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barrier Product: Cray XMT
In code, a barrier is used after a phase. The barrier delays the streams that were executing parallel operations in the phase until all the streams from the phase reach the barrier. Once all the streams reach the barrier, the streams begin work on the next phase.
blade Product: Cray XMT
1) A field-replaceable physical entity. A Cray XMT service blade consists of AMD Opteron sockets, memory, Cray SeaStar chips, PCI-X or PCIe cards, and a blade control processor. A Cray XMT compute blade consists of Threadstorm processors, memory, Cray SeaStar chips, and a blade control processor. 2) From a system management perspective, a logical grouping of nodes and blade control processor that monitors the nodes on that blade.
blade control processor Product: Cray X2, Cray XMT, Cray XT series, Cray XE series
A microprocessor on a blade that communicates with a cabinet control processor through the HSS network to monitor and control the nodes on the blade. See also blade L0 controller Hardware Supervisory System (HSS)
block scheduling Product: Cray XMT
Method of thread execution used by the compiler where contiguous blocks of loop iterations are divided equally and assigned to available streams. For example, if there are 100 loop iterations and 10 streams, the compiler assigns 10 iterations to each stream. The advantage to this method is that data in registers can be reused across adjacent iterations rather than releasing a stream after each iteration.
cabinet control processor Product: Cray X2, Cray XE series, Cray XMT, Cray XT series
A microprocessor in the cabinet that communicates with the HSS via the HSS network to monitor and control the devices in a system cabinet. See also Hardware Supervisory System (HSS)
cage Product: Cray XMT
A chassis on a Cray XMT series system. See chassis
chassis Product: Cray XMT
The hardware component of a Cray XMT cabinet that houses blades. Each cabinet contains three vertically stacked chassis, and each chassis contains eight vertically mounted blades. See also cage
Cray SeaStar chip Product: Cray XMT
The component of the system interconnection network that provides message routing and communication services. See also system interconnection network
dependence analysis Product: Cray XMT
A technique used by the compiler to determine if any iteration of a loop depends on any other iteration (this is known as a loop-carried dependency).
dynamic scheduling Product: Cray XMT
In a dynamic schedule, the compiler does not bind iterations to streams at loop startup. Instead, streams compete for each iteration using a shared counter.
future Product: Cray XMT
Implements user-specified or explicit parallelism by starting new threads. A future is a sequence of code that can be executed by a newly created thread that is running concurrently with other threads in the program. Futures delay the execution of code if the code is using a value that is computed by a future, until the future completes. The thread that spawns the future uses parameters to pass information from the future to the waiting thread, which then executes. In a program, the term future is used as a type qualifier for a synchronization variable or as a keyword for a future statement.
induction variable Product: Cray XMT
A variable that is increased or decreased by a fixed amount on each iteration of a loop.
inductive loop Product: Cray XMT
An inductive loop is one which contains no loop-carried dependencies and has the following characteristics: a single entrance at the top of the loop; controlled by an induction variable; and has a single exit that is controlled by comparing the induction variable against an invariant.
interleaved scheduling Product: Cray XMT
Method of executing loop iterations used by the compiler where contiguous iterations are assigned to distinct streams. For example, for a loop with 100 iterations and 10 streams, one stream performs iterations 1, 11, 21,... while another stream performs iterations 2, 12, 22, ..., and so on. This method is typically used for triangular loops because it reduces imbalances. One disadvantage to using this method is that there is loss of data reuse between loop iterations because the stream is released at the end of the iteration.
L0 processor Product: Cray XMT
See blade control processor
linear recurrence Product: Cray XMT
A special type of recurrence that can be parallelized.
logical machine Product: Cray XMT
An administrator-defined portion of a physical Cray XMT system, operating as an independent computing resource.
loop-carried dependences Product: Cray XMT
The value from one iteration of a loop is used during a subsequent iteration of the loop. This type of loop cannot be parallelized by the compiler.
multicore Product: Cascade, Cray X2, Cray XMT, Cray XT series
A processor that combines multiple independent execution engines ("cores"), each with its own cache and cache controller.
multiprocessor mode Product: Cray XMT
A mode that can be set at compile time that ensures that when the compiled application is run, iterations of a loop are run on multiple processors.
node Product: Cray XT series, Cray XMT, Cray XE series, Cray X2
For CLE systems, the logical group of processor(s), memory, and network components that acts as a network end point on the system interconnection network.
phase Product: Cray XMT
A set of one or more sections of code that the stream executes in parallel. Each section contains an iteration of a loop. Phases and sections are contained in control flow code generated by the compiler to control the parallel execution of a function.
recurrence Product: Cray XMT
A recurrence occurs when a loop uses values computed in one iteration in subsequent iterations. These subsequent uses of the value imply loop-carried dependences and thus usually prevent parallelization. To increase parallelization, use linear recurrence.
reduction Product: Cray XMT
A simple form of recurrence that reduces a large amount of data to a single value. It is commonly used to find the minimum and maximum elements of a vector. Although similar to a reduction, it is easier to parallelize and uses less memory.
region Product: Cray XMT
A region is an area in code where threads are forked in order to perform a parallel operation. The region ends at the point where the threads join back together at the end of the parallel operation.
service node Product: Cray XMT
Performs support functions for applications and system services such as login, network, I/O, boot, and service database (SDB). Service nodes run a version of CLE.
single-processor mode Product: Cray XMT
A mode that can be set at compile time that ensures that when the compiled application is run, iterations of a loop are run on a single processor.
Source :
http://docs.cray.com/cgi-bin/craydoc.cgi?mode=Glossary;q=product%3dxmt
Knowledge Base
http://docs.cray.com/kbase/plat.html
Accéder au manuel utilisateur
Overview of Gemini Hardware Counters
http://docs.cray.com/books/S-0025-10//S-0025-10.pdf
Accéder au manuel utilisateur
TotalView
New Feature
http://docs.cray.com/books/S-6503-65/S-6503-65.pdf
Accéder au manuel utilisateur
PGI® User’s Guide Parallel Fortran, C and C++ for Scientists and Engineers :
http://docs.cray.com/books/S-6516-71/S-6516-71-apr08.pdf
Accéder au manuel utilisateur
About the guide :
http://docs.cray.com/books/004-2182-003/03preface.pdf
Scienti?c Libraries User’s Guide
004–2151–002
http://docs.cray.com/books/004-2151-002//004-2151-002-manual.pdf
PGI
®
User’s Guide
Parallel Fortran, C and C++
for Scientists and Engineer
http://docs.cray.com/books/S-6516-61/pgi61ug.pdf
PGI®
User’s Guide
Parallel Fortran, C and C++ for Scientists and
Engineers
http://docs.cray.com/books/S-6516-70/S-6516-70-mar07.pdf
PAPI USER’S GUIDE
http://docs.cray.com/books/S-6515-35/S-6515-35.pdf
SuperLU Users' Guide
James W. Demmel
1
John R. Gilbert
2 Xiaoye S. Li
3
Septemb er, 1999
Last update: October, 2003
http://docs.cray.com/books/S-6532-10/ug.pdf
SuperLU Users’ Guide
James W. Demmel
1
John R. Gilbert
2 Xiaoye S. Li
3
September 1999
Last update: June 2009
http://docs.cray.com/books/S-6532-20/6532-20.pdf
February 2011 Programming Environments Release Announcement
http://docs.cray.com/books/S-9401-1102//S-9401-1102.pdf
Guide to Parallel Vector Applications
004–2182–003
http://docs.cray.com/books/004-2182-003/004-2182-003-manual.pdf
CrayDoc™ Installation and
Administration Guide
S–2340–21
http://docs.cray.com/books/S-2340-21/S-2340-21-manual.pdf
Comparing Binaries Between Cray Linux Environment
(CLE) Systems, Standalone Whiteboxes, and ESLogin
Nodes
http://docs.cray.com/books/S-0019-10//S-0019-10.pdf
Cray Application Developer's Environment User's
Guid
http://docs.cray.com/books/S-2396-601/S-2396-601.pdf
Cray Application Developer's Environment User's
Guide
http://docs.cray.com/books/S-2396-60/S-2396-60.pdf
Cray Application Developer's Environment User's
Guid
http://docs.cray.com/books/S-2396-50/S-2396-50.pdf
AMD Core Math Library (ACML)
Version 4.3.0
http://docs.cray.com/books/S-6511-43/S-6511-43.pdf
AMD Core Math Library (ACML)
Version 4.0.0
http://docs.cray.com/books/S-6511-40/acml_400_userguide.pdf
Cray Fortran Reference Manual
http://docs.cray.com/books/S-3901-80/S-3901-80.pdf
Cray C and C++ Reference Manual
http://docs.cray.com/books/S-2179-80/S-2179-80.pdf
Lustre File System
Operations Manual - Version 1.8
http://docs.cray.com/books/S-6540-1815/S-6540-1815.pdf
Cray Linux Environment™ (CLE) 4.0 Software Release
Overvie
http://docs.cray.com/books/S-2425-40/S-2425-40.pdf
Cray XT™ System Overview :
http://docs.cray.com/books/S-2423-22/S-2423-22.pdf
Cray X1™ Series System Overview
S–2346–25
http://docs.cray.com/books/S-2346-25/S-2346-25.pdf
Migrating Applications to the
Cray X1™ Series Systems
S–2378–54
http://docs.cray.com/books/S-2378-54/S-2378-54.pdf
intro_biolib(3)
http://docs.cray.com/cgi-bin/craydoc.cgi?idx=man_search;q=id%3dintro_biolib.3;mode=Show;f=man/biolibm/30/cat3/intro_biolib.3.html
Getting Started on Cray X2™
Systems
S–2471–60 :
http://docs.cray.com/books/S-2471-60/S-2471-60.pdf
Cray XT5h
™ System Overview
S–2472–21 :
http://docs.cray.com/books/S-2472-21/S-2472-21.pdf
Cray®
Programming Environment
6.0 Releases Overview and
Installation Guide
S–5212–60
http://docs.cray.com/books/S-5212-60/S-5212-60.pdf
Cray®
Fortran Reference Manual
S–3901–60
http://docs.cray.com/books/S-3901-60/S-3901-60.pdf
Cray®
C and C++ Reference
Manual
S–2179–60 :
http://docs.cray.com/books/S-2179-60/S-2179-60.pdf
Cray Performance Analysis Tools 5.3 Release
Overview and Installation Guid
http://docs.cray.com/books/S-2474-53/S-2474-53.pdf
Cray XMT™ System Overview
http://docs.cray.com/books/S-2466-20/S-2466-20.pdf
Cray XMT™ Programming Environment User's Guide
http://docs.cray.com/books/S-2479-20/S-2479-20.pdf
Cray XMT™ Programming Model
http://docs.cray.com/books/S-2367-20/S-2367-20.pdf
Cray XMT™ Debugger Reference Guid
http://docs.cray.com/books/S-2467-20/S-2467-20.pdf
Cray XMT™ Performance Tools User's Guide
http://docs.cray.com/books/S-2462-20/S-2462-20.pdf
Optimizing Loop-Level Parallelism in Cray XMT™
Applications :
http://docs.cray.com/books/S-2487-14/S-2487-14.pdf
Limiting Loop Parallelism in Cray XMT™ Applications
June 21, 2010
http://docs.cray.com/books/S-0027-14/S-0027-14.pdf
Cray DVS Installation and
Configuration
Private
S–0005–10
http://docs.cray.com/books/S-0005-10//S-0005-10.pdf
Application Cleanup by ALPS and Node Health Monitoring :
http://docs.cray.com/books/S-0014-22/S-0014-22.pdf
Application Programmer’s I/O
Guide
S–3695–36 :
http://docs.cray.com/books/S-3695-36/S-3695-36-manual.pdf
Overview of Gemini Hardware Counters
This document describes the Gemini Performance Counters and how to use them to
optimize individual applications and system traf?c.
Send e-mail to docs@cray.com with any comments that will help us to improve the
accuracy and usability of this document. Be sure to include the title and number
of the document with your comments. We value your comments and will respond
to them promptly.
Accessing network performance counters is desirable for application developers,
system library developers (e.g. MPI), and system administrators. Application
developers want to improve their application run-times or measure what affect other
traf?c on the system has on their application. System library developers want to
optimize their collective operations. System Administrators want to observe the
system, looking for hotspots. Effective with the CrayPat (Cray performance analysis
tool) version 5.1 and Cray Linux Environment (CLE) version 3.1 software releases
for the Cray XE platform, users can monitor many of the performance counters that
reside on the Gemini networking chip.
There are two categories of Gemini performance counters available to users. NIC
performance counters record information about the data moving through theNetwork
Interface Controller (NIC). On the Gemini ASIC there are two NICs, each attached
to a compute node. Thus, the data from the NIC performance counters re?ects
network transfers beginning and ending on the node. These performance counters
are read-only.
Network router tile counters are available on a per-Gemini basis. There are both
read-only and read/write tile counters. Each chip has 48 router tiles, arranged in a
6x8 grid. Eight processor tiles connect to each of the two Gemini NICs. Each NIC
connects to a different node, running separate Linux instances.
If collection at other points of the application is desired, use the CrayPat API to
insert regions as described in the pat_build man page. It is recommended that
you do not collect any other performance data when collecting network counters.
Data collection of network counters is much more expensive than other performance
data collection, and will skew other results. At the time the instrumented executable
program is launched with the aprun command, a set of environment variables,
PAT_RT_NWPC_*, provide access to the Gemini network performance counters.
These environment variables are described in the intro_craypat man page.
S–0025–10 1Using the Cray Gemini Hardware Counters
1.1 Using CrayPat to Monitor Gemini Counters
The CrayPat utility pat_build instruments an executable ?le. One aspect of the
instrumentation includes intercepting entries into and returns out of a function. This
is known formally as tracing. Information such as time stamps and performance
counter values are recorded at this time.
CrayPat supports instrumentation of an application binary for collection of Gemini
counters. Counter values are recorded at application runtime, and are presented to the
user through a table generated by pat_report. The CrayPat user interface to request
instrumentation is similar to that for processor performance counters. There is no
Gemini counter display available in Cray Apprentice2 at this time. A new display will
be available in a subsequent release of the Cray Apprentice2 software.
Although the user interface to request network counters is similar to processor
counters, there are some signi?cant differences that must be understood. Depending
on the type of counters requested, some are shared across all processors within a
node, some are shared between two nodes and some are shared across all applications
passing through a chip. Some counters monitor all traf?c for your application, even
on nodes that are not reserved for your application, and some monitor locally, that is
they monitor only traf?c associated with nodes assigned to a Gemini chip and no
other traf?c from the network.
Users should also be aware that access to the network counters is more
resource-intensive than access to the processor performance counters. Because
Gemini counters are a shared resource, the system software is designed to provide
dedicated access whenever possible. This is done through the Application Level
Placement Scheduler (ALPS) by ensuring that an application collecting counters is
not placed on the same Gemini chip as another application collecting performance
counters. It does not prevent a second application from being placed on the same
Gemini chip that is not collecting counters however. This compromise assures better
system utilization because compute nodes are not left unavailable for use by another
application.
The CrayPat 5.1 release focuses on the use of the NIC and ORB counters available
within the Gemini chip. The values collected from these counters are local to a
node and therefore speci?c to an application. Traf?c between MPI ranks cannot be
distinguished through the counters. The event names that CrayPat supports are listed
at the end of this document. Network counters are only collected for the MAIN
thread. Values are collected at the beginning and end of the instrumented application.
Instrumentation overhead is minimal. This gives a high-level view of the program's
use of the networking router in terms of the counters speci?ed. Currently the time to
access counter data is too expensive to collect more frequently. A future release of
CLE will address these performance limitations.
2 S–0025–10Overview of Gemini Hardware Counters
Before attempting the following examples verify that your system has a Gemini
network:
$ module list
xtpe-network-gemini
Attempting to collect Gemini performance counters on a system that does not have
the Gemini network will result in a fatal error:
$ aprun -n 16 my_program+pat
CrayPat/X: Version 5.1 Revision 3329 05/20/10 11:26:16
pat[FATAL][0]: initialization of NW performance counter API failed
[No such file or directory]
Example 1. Collect stalls associated with node traf?c to and from the network
This example enables tracing of MAIN.
$ pat_build -w my_program
$ export PAT_RT_NWPC=GM_ORB_PERF_VC0_STALLED,GM_ORB_PERF_VC1_STALLED
$ aprun my_program+pat
Example 2. Display network counter data
$ pat_report my_program+pat+11171-41tdot.xf> counter_rpt
Example output from pat_report:
NWPC Data by Function Group and Function Group / Function / Node Id=0='HIDE'
=====================================================================
Total
---------------------------------------------------------------------
Time% 100.0%
Time 2.476423 secs
GM_ORB_PERF_VC1_STALLED 0
GM_ORB_PERF_VC1_BLOCKED 0
GM_ORB_PERF_VC1_BLOCKED_PKT_GEN 0
GM_ORB_PERF_VC1_PKTS 48
GM_ORB_PERF_VC1_FLITS 48
GM_ORB_PERF_VC0_STALLED 111
GM_ORB_PERF_VC0_PKTS 48
GM_ORB_PERF_VC0_FLITS 201
=====================================================================
S–0025–10 3Using the Cray Gemini Hardware Counters
Example 3. Collect data for a custom group of network counters
In this example a user creates a group of network events in a ?le called
my_nwpc_groups, one called 1 and the other called CQ_AMO:
$ cat my_nwpc_groups
# Group 1: Outstanding Request Buffer
1 =
GM_ORB_PERF_VC1_STALLED,
GM_ORB_PERF_VC1_BLOCKED,
GM_ORB_PERF_VC1_BLOCKED_PKT_GEN,
GM_ORB_PERF_VC1_PKTS,
GM_ORB_PERF_VC1_FLITS,
GM_ORB_PERF_VC0_STALLED,
GM_ORB_PERF_VC0_PKTS,
GM_ORB_PERF_VC0_FLITS
# Group CQ_AMO:
CQ_AMO =
GM_AMO_PERF_COUNTER_EN,
GM_AMO_PERF_CQ_FLIT_CNTR,
GM_AMO_PERF_CQ_PKT_CNTR,
GM_AMO_PERF_CQ_STALLED_CNTR,
GM_AMO_PERF_CQ_BLOCKED_CNTR
$ pat_build -w my_program
$ export PAT_RT_NWPC_FILE=my_nwpc_groups
$ export PAT_RT_NWPC=1,CQ_AMO
$ aprun -n16 my_program+pat
4 S–0025–10Overview of Gemini Hardware Counters
Example output from pat_report:
NWPC Data by Function Group and Function
Group / Function / Node Id=0='HIDE'
=====================================================================
Total
---------------------------------------------------------------------
Time% 100.0%
Time 2.639046 secs
GM_ORB_PERF_VC1_STALLED 72525
GM_ORB_PERF_VC1_PKTS 50457
GM_AMO_PERF_COUNTER_EN 0
GM_AMO_PERF_CQ_FLIT_CNTR 11752
GM_AMO_PERF_CQ_PKT_CNTR 5876
GM_AMO_PERF_CQ_STALLED_CNTR 5092
GM_AMO_PERF_CQ_BLOCKED_CNTR 29
=====================================================================
Example 4. Suppress instrumented entry points from recording performance
data to reduce overhead
This example assumes a NWPC group FMAS exists and is available for use. Because
the program is traced, the PAT_RT_TRACE_FUNCTION_NAME is set to suppress
any data collection by already instrumented entry points in my_program+pat. This
means that NWPC values will only be recorded for the MAIN thread at the start and
the end of the instrumented program. Instrumentation overhead is minimal.
$ pat_build -u -g mpi my_program
$ export PAT_RT_NWPC=FMAS
$ export PAT_RT_TRACE_FUNCITON_NAME=*:0
$ aprun -n32 my_program+pat
This gives a high-level view of the program's use of the networking router in terms of
what the FMAS group describes. If more details about NWPC use during execution
of the program are desired, the PAT_RT_TRACE_FUNCTION_NAME environment
variable need not be set, but the signi?cant overhead injected by reading the NWPCs
may make the resulting performance data inaccurate.
To selectively collect NWPCs and the other performance data for traced functions,
add them to the end of PAT_RT_TRACE_FUNCTION_NAME:
$ export PAT_RT_TRACE_FUNCTION_NAME=0:*,mxm,MPI_Bcast
S–0025–10 5Using the Cray Gemini Hardware Counters
1.2 Gemini NIC Counters
To better understand how to use the NIC counters, you need to understand some of
the terminology speci?c to the Gemini network architecture.
The Block Transfer Engine (BTE)
A Gemini network packet typically consists of one or more ?its, which are the units
of ?ow control for the network. Because ?its are usually larger than the physical
datapath, they are divided into phits, which are the units of data that the network can
handle physically. A packet must contain at least two phits, one for the header and
one for the cyclical redundancy check (CRC).
The V0 counters support the request channel and the V1 counters support the
response channel. A ?it/pkt ratio can tell the user if the data entering the network was
not aligned, eg a ratio greater than 1 indicates misaligned data is being sent across
the network. Because there is a bandwidth/pipe size difference between outgoing
and incoming (outgoing is smaller), in general you will notice more stalls on the V0
(request) channel.
The following counters are recommended as a way to begin using the Gemini NWPC:
GM_ORB_PERF_VC0_STALLED
GM_ORB_PERF_VC1_STALLED
GM_ORB_PERF_VC0_PKTS
GM_ORB_PERF_VC1_PKTS
GM_ORB_PERF_VC0_FLITS
GM_ORB_PERF_VC1_FLITS
Table 1. Atomic Memory Operations Performance Counters
Name Description
GM_AMO_PERF_ACP_COMP_CNTR Number of Atomic Memory Operation (AMO)
computations that have occurred.
GM_AMO_PERF_ACP_MEM_UPDATE_CNTR Number of AMO logic cache write-throughs that
have occurred.
GM_AMO_PERF_ACP_STALL_CNTR Number of AMO logic pipeline stalls that have
occurred.
GM_AMO_PERF_AMO_HEADER_CNTR Number of request headers processed by
the Decode Logic that have had an AMO
computation. Error packets are not counted.
GM_AMO_PERF_COUNTER_EN When set, counting is enabled. When cleared,
counting is disabled.
GM_AMO_PERF_CQ_BLOCKED_CNTR Number of cycles the CQ FIFO is blocked.
6 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_AMO_PERF_CQ_FLIT_CNTR Number of ?its (network ?ow control units) that
are read from the CQ FIFO.
GM_AMO_PERF_CQ_PKT_CNTR Number of packets that are read from the CQ
FIFO.
GM_AMO_PERF_CQ_STALLED_CNTR Number of cycles the CQ FIFO is stalled.
GM_AMO_PERF_DONE_INV_CNTR Number of times a valid cache entry was
invalidated because there were no more
outstanding AMO requests targeting it and the last
request did not have the cacheable bit set.
GM_AMO_PERF_ERROR_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had errors.
GM_AMO_PERF_FLUSH_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had a Flush command.
Error packets are not counted.
GM_AMO_PERF_FULL_INV_CNTR Number of times a valid but inactive cache entry
was invalidated to make room for a new AMO
address. A high value in this counter indicates that
there are too many cacheable AMO addresses and
that the cache is being thrashed.
GM_AMO_PERF_GET_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had an GET command.
Error packets are not counted.
GM_AMO_PERF_MSGCOMP_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had a MsgComplete
command. Error packets are not counted.
GM_AMO_PERF_PUT_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had an PUT command.
Error packets are not counted.
GM_AMO_PERF_REQLIST_FULL_STALL_CNTR Number of times an AMO request causes the NRP
to stall waiting for a Request List entry to become
free.
GM_AMO_PERF_RMT_BLOCKED_CNTR Number cycles the RMT FIFO is blocked
GM_AMO_PERF_RMT_FLIT_CNTR Number of ?its that are read from the RMT FIFO
GM_AMO_PERF_RMT_PKT_CNTR Number of packets that are read from the RMT
FIFO
GM_AMO_PERF_RMT_STALLED_CNTR Number cycles the RMT FIFO is stalled
S–0025–10 7Using the Cray Gemini Hardware Counters
Name Description
GM_AMO_PERF_TAG_HIT_CNTR Number of AMO requests that have been
processed in the Tag Store and have resulted in a
cache hit.
GM_AMO_PERF_TAG_MISS_CNTR Number of AMO requests that have been
processed in the Tag Store and have resulted in a
cache miss.
GM_AMO_PERF_TAG_STALL_CNTR Number of times a GET/PUT request hits in the
cache and causes the NRP to stall.
Table 2. Fast Memory Access Performance Counters
Name Description
GM_FMA_PERF_CQ_PKT_CNT Number of packets from Fast Memory Access
(FMA) to CQ.
GM_FMA_PERF_CQ_STALLED_CNT Number of clock cycles FMA_CQ was stalled due to
lack of credits.
GM_FMA_PERF_HT_NP_REQ_FLIT_CNT Number of HT NP request ?its to FMA.
GM_FMA_PERF_HT_NP_REQ_PKT_CNT Number of HT NP request packets to FMA.
GM_FMA_PERF_HT_P_REQ_FLIT_CNT Number of HT P request ?its to FMA.
GM_FMA_PERF_HT_P_REQ_PKT_CNT Number of HT P request packets to FMA.
GM_FMA_PERF_HT_RSP_PKT_CNT Number of HT response packets from FMA to HT.
GM_FMA_PERF_HT_RSP_STALLED_CNT Number of clock cycles FMA_HT_RSP was stalled
due to lack of credits.
GM_FMA_PERF_TARB_FLIT_CNT Number of ?its from FMA to TARB.
GM_FMA_PERF_TARB_PKT_CNT Number of packets from FMA to TARB.
GM_FMA_PERF_TARB_STALLED_CNT Number of clock cycles FMA_TARB was stalled
due to lack of credits.
8 S–0025–10Overview of Gemini Hardware Counters
Table 3. Hyper-transport Arbiter Performance Counters
Name Description
GM_HARB_PERF_AMO_NP_BLOCKED Number of times AMO Non-Posted Queue has an
entry, but is blocked from using the Non-Posted
Initiator Request output channel by the BTE
Non-Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_NP_FLITS Number of ?its coming out of the AMO Non-Posted
Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_NP_PKTS Number of packets coming out of the AMO
Non-Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_NP_STALLED Number of cycles the AMO Non-Posted Queue
is stalled due to a lack credits on the Non-Posted
Initiator Request channel. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_ACP_BLOCKED Number of times AMO Posted AMO Computation
Pipe Queue has an entry, but is blocked from
using the Posted Initiator Request output channel
by another Posted Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_ACP_FLITS Number of ?its coming out of the AMO Posted
AMO Computation Pipe Queue. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
S–0025–10 9Using the Cray Gemini Hardware Counters
Name Description
GM_HARB_PERF_AMO_P_ACP_PKTS Number of packets coming out of the AMO Posted
AMO Computation Pipe Queue. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_ACP_STALLED Number of cycles the AMO Posted AMO
Computation Pipe Queue is stalled due to a lack
credits on the Posted Initiator Request channel.
The Local Block has read/write access to the full
counter. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_BLOCKED Number of times AMO Posted New Request Pipe
Queue has an entry, but is blocked from using the
Posted Initiator Request output channel by another
Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_FLITS Number of ?its coming out of the AMO Posted
New Request Pipe Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_PKTS Number of packets coming out of the AMO Posted
New Request Pipe Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_STALLED Number of cycles the AMO Posted New Request
Pipe Queue is stalled due to a lack credits on the
Posted Initiator Request channel. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
10 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_HARB_PERF_BTE_NP_BLOCKED Number of times AMO Non-Posted BTE Queue has
an entry, but is blocked from using the Non-Posted
Initiator Request output channel by another
Non-Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_NP_FLITS Number of ?its coming out of the AMO Non-Posted
BTE Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_NP_PKTS Number of packets coming out of the AMO
Non-Posted BTE Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_NP_STALLED Number of cycles the AMO Non-Posted BTE Queue
is stalled due to a lack credits on the Posted Initiator
Request channel. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_P_BLOCKED Number of times AMO Posted BTE Queue has an
entry, but is blocked from using the Posted Initiator
Request output channel by another Posted Queue.
The Local Block has read/write access to the full
counter. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_BTE_P_FLITS Number of ?its coming out of the AMO Posted
BTE Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
S–0025–10 11Using the Cray Gemini Hardware Counters
Name Description
GM_HARB_PERF_BTE_P_PKTS Number of packets coming out of the AMO Posted
BTE Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_P_STALLED Number of cycles the AMO Posted BTE Queue is
stalled due to a lack credits on the Posted Initiator
Request channel. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_COUNTER_EN When set, counting is enabled. When clear, counting
is disabled. This MMR is reset by the chip reset
(i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_NP_FLITS Number of ?its on the non-posted initiator request
output of the HARB block. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_IREQ_NP_PKTS Number of packets on the non-posted initiator
request output of the HARB Block. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_NP_STALLED Number of cycles on the non-posted initiator request
output of the HARB is stalled due to a lack credits
on the Non-Posted Initiator Request channel. The
Local Block has read/write access to the full counter.
Bits 63:48 of this MMR are unimplemented and
always return zero. This MMR is reset to all zeros
by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
12 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_HARB_PERF_IREQ_P_FLITS Number of ?its on the posted initiator request output
of the HARB block. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. Bits
63:48 of this MMR are unimplemented and always
return zero. This MMR is reset to all zeros by the
chip reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_P_PKTS Number of packets on the posted initiator request
output of the HARB Block. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_P_STALLED Number of cycles on the posted initiator request
output of the HARB is stalled due to a lack credits
on the Posted Initiator Request channel. The Local
Block has read/write access to the full counter. Bits
63:48 of this MMR are unimplemented and always
return zero. This MMR is reset to all zeros by the
chip reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_RAT_P_BLOCKED Number of times AMO Posted RAT Queue has an
entry, but is blocked from using the Posted Initiator
Request output channel by another Posted Queue.
The Local Block has read/write access to the full
counter. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_RAT_P_FLITS Number of ?its coming out of the AMO Posted
RAT Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
S–0025–10 13Using the Cray Gemini Hardware Counters
Name Description
GM_HARB_PERF_RAT_P_PKTS Number of packets coming out of the AMO Posted
RAT Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_RAT_P_STALLED Number of cycles the AMO Posted RAT Queue is
stalled due to a lack credits on the Posted Initiator
Request channel. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
Table 4. Network Address Translation Performance Counters
Name Description
GM_NAT_PERF_BTE_BLOCKED Number of cycles a BTE translation is blocked due
to arbitration loss.
GM_NAT_PERF_BTE_STALLED Number of cycles a BTE translation is stalled due to
MMR access.
GM_NAT_PERF_BTE_TRANSLATIONS Number of translations performed for the BTE
interface.
GM_NAT_PERF_COUNTER_EN When set, counting is enabled. When cleared,
counting is disabled.
GM_NAT_PERF_REQ_BLOCKED Number of cycles a REQ translation is blocked due
to arbitration loss.
GM_NAT_PERF_REQ_STALLED Number of cycles a REQ translation is stalled due to
MMR access.
GM_NAT_PERF_REQ_TRANSLATIONS Number of translations performed for the REQ
interface.
GM_NAT_PERF_RSP_BLOCKED Number of cycles a RSP translation is blocked due
to arbitration loss.
GM_NAT_PERF_RSP_STALLED Number of cycles a RSP translation is stalled due to
MMR access.
GM_NAT_PERF_RSP_TRANSLATIONS Number of translations performed for the RSP
interface.
GM_NAT_PERF_TRANS_ERROR0 Number of translations that failed due to error 0
(Uncorrectable error in translation).
14 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_NAT_PERF_TRANS_ERROR1 Number of translations that failed due to error 1
(VMDH table invalid entry).
GM_NAT_PERF_TRANS_ERROR2 Number of translations that failed due to error 2
(MDDT/MRT invalid or illegal entry).
GM_NAT_PERF_TRANS_ERROR3 Number of translations that failed due to error 3
(Protection tag violation).
GM_NAT_PERF_TRANS_ERROR4 Number of translations that failed due to error 4
(memory bounds error).
GM_NAT_PERF_TRANS_ERROR5 Number of translations that failed due to error 5
(write permission error)
Table 5. Netlink Performance Counters
Name Description
GM_NL_PERF_ALL_LCBS_REQS_TO_NIC_0_STALLED Number of ticks all LCBs requests have
stalled to NIC 0.
GM_NL_PERF_ALL_LCBS_REQS_TO_NIC_1_STALLED Number of ticks all LCBs requests have
stalled to NIC 1.
GM_NL_PERF_ALL_LCBS_RSP_TO_NIC_0_STALLED Number of ticks all LCBs responses have
stalled to NIC 0.
GM_NL_PERF_ALL_LCBS_RSP_TO_NIC_1_STALLED Number of ticks all LCBs responses have
stalled to NIC 1.
GM_NL_PERF_CNTRL Controls the performance counters.
Writing a 1 to the Start ?eld starts the
counters. Writing a 1 to the Stop ?eld
stops the counters. Writing a 1 to the
Clear ?eld clears the counters.
GM_NL_PERF_LCB_n_REQ_CMP_22 Decompressed request data to two phit
LCB_n, where n is a value from 0 to 7
that speci?es the LCB.
GM_NL_PERF_LCB_n_REQ_CMP_44 Decompressed request data to one phit
LCB_n, where n is a value from 0 to 7
that speci?es the LCB.
GM_NL_PERF_LCB_n_REQ_TO_NIC_0 Number of requests from LCB_n to NIC
0.
GM_NL_PERF_LCB_n_REQ_TO_NIC_0_STALLED Number of ticks LCB_n requests are
blocked to NIC 0.
GM_NL_PERF_LCB_n_REQ_TO_NIC_1 Number of requests from LCB_n to NIC
1.
S–0025–10 15Using the Cray Gemini Hardware Counters
Name Description
GM_NL_PERF_LCB_n_REQ_TO_NIC_1_STALLED Number of ticks LCB_n requests are
blocked to NIC 1.
GM_NL_PERF_LCB_n_REQ_TO_PHITS Number of request phits received on
LCB_n.
GM_NL_PERF_LCB_n_REQ_TO_PKTS Number of request packets received on
LCB_n.
GM_NL_PERF_LCB_n_RSP_CMP_22 Decompressed response data to two phit
LCB_n
GM_NL_PERF_LCB_n_RSP_TO_NIC_1 Number of responses from LCB_n to
NIC 1.
GM_NL_PERF_LCB_n_RSP_TO_NIC_1_STALLED Number of ticks LCB_n responses are
blocked to NIC 1.
GM_NL_PERF_NIC_0_REQ_STALLED_TO_ALL_LCBS Number of ticks NIC_0 requests are
blocked to all LCBs.
GM_NL_PERF_NIC_0_REQ_TO_LCB_n Number of requests from NIC_0 LCB_
n.
GM_NL_PERF_NIC_0_REQ_TO_LCB_n_STALLED Number of ticks NIC_0 requests are
blocked to LCB_n.
GM_NL_PERF_NIC_0_RSP_STALLED_TO_ALL_LCBS Number of ticks NIC_0 responses are
blocked to all LCBs.
GM_NL_PERF_NIC_0_RSP_TO_LCB_n Number of responses from NIC_0 LCB_
n.
GM_NL_PERF_NIC_0_RSP_TO_LCB_n_STALLED Number of ticks NIC_0 responses are
blocked to LCB_n.
GM_NL_PERF_NIC_1_REQ_STALLED_TO_ALL_LCBS Number of ticks NIC_0 requests are
blocked to all LCBs.
GM_NL_PERF_NIC_1_REQ_TO_LCB_n Number of requests from NIC_1 to
LCB_ n.
GM_NL_PERF_NIC_1_REQ_TO_LCBn_STALLED Number of ticks NIC_1 requests are
blocked to LCB_n.
GM_NL_PERF_NIC_1_RSP_STALLED_TO_ALL_LCBS Number of ticks NIC_1 responses are
blocked to all LCBs.
GM_NL_PERF_NIC_1_RSP_TO_LCB_n Number of responses from NIC_1 LCB_
n.
GM_NL_PERF_NIC_1_RSP_TO_LCB_n_STALLED Number of ticks NIC_1 responses are
blocked to LCB_n.
16 S–0025–10Overview of Gemini Hardware Counters
Table 6. NPT Performance Counters
Name Description
GM_NPT_PERF_ACP_BLOCKED_CNTR Number of cycles the ACP FIFO is blocked.
GM_NPT_PERF_ACP_FLIT_CNTR Number of ?its that are read from the ACP FIFO.
GM_NPT_PERF_ACP_PKT_CNTR Number of packets that are read from the ACP
FIFO.
GM_NPT_PERF_ACP_STALLED_CNTR Number of cycles the ACP FIFO is stalled.
GM_NPT_PERF_BTE_RSP_PKT_CNTR Number of packets that are sent to the Netlink as Get
or Flush responses.
GM_NPT_PERF_COUNTER_EN Provides the count enable.
GM_NPT_PERF_FILL_RSP_PKT_CNTR Number of packets that are sent to the AMO block
as ?ll responses.
GM_NPT_PERF_HTIRSP_ERR_CNTR Number of packets that are received from the HT
cave and have an error status.
GM_NPT_PERF_HTIRSP_FLIT_CNTR Number of ?its that are received from the HT cave.
GM_NPT_PERF_HTIRSP_PKT_CNTR Number of packets that are received from the HT
cave.
GM_NPT_PERF_LB_BLOCKED_CNTR Number of cycles the LB FIFO is blocked.
GM_NPT_PERF_LB_FLIT_CNTR Number of ?its that are read from the LB FIFO.
GM_NPT_PERF_LB_PKT_CNTR Number of packets that are read from the LB FIFO.
GM_NPT_PERF_LB_STALLED_CNTR Number of cycles the LB FIFO is stalled.
GM_NPT_PERF_NL_RSP_PKT_CNTR Number of packets that are sent to the AMO block
as ?ll responses.
GM_NPT_PERF_NPT_BLOCKED_CNTR Number of cycles the NPT FIFO is blocked.
GM_NPT_PERF_NPT_FLIT_CNTR Number of ?its that are read from the NPT FIFO.
GM_NPT_PERF_NPT_PKT_CNTR Number of packets that are read from the NPT FIFO.
GM_NPT_PERF_NPT_STALLED_CNTR Number of cycles the NPT FIFO is stalled.
GM_NPT_PERF_NRP_BLOCKED_CNTR Number of cycles the NRP FIFO is blocked.
GM_NPT_PERF_NRP_FLIT_CNTR Number of ?its that are read from the NRP FIFO.
GM_NPT_PERF_NRP_PKT_CNTR Number of packets that are read from the NRP
FIFO.
GM_NPT_PERF_NRP_STALLED_CNTR Number of cycles the NRP FIFO is stalled.
S–0025–10 17Using the Cray Gemini Hardware Counters
Table 7. ORB Performance Counters
Name Description
GM_ORB_PERF_VC0_FLITS Number of ?its to come into the TX Input Queue
from the SSID.
GM_ORB_PERF_VC0_PKTS Number of packets to come into the TX Input Queue
from the SSID.
GM_ORB_PERF_VC0_STALLED Number of packets not given access to the TX
Control Logic because there is not enough credits
available from the NL Block, or there are no
available memory locations from the ORD RAM,
or a tail ?it has not been received in the ORB Input
Queue when performing store-and-forward.
GM_ORB_PERF_VC1_BLOCKED Number of packets not given access to the RX
Control Logic because the read address and write
address into the ORD RAM are attempting to access
the same bank of the ORD RAM or because there
is a read access to the ORD RAM from the Local
Block.
GM_ORB_PERF_VC1_BLOCKED_PKT_GEN Number of times the RX Response FIFO is blocked
because a packet in the RX Control Logic is being
translated into the format used by the rest of the
NIC.
GM_ORB_PERF_VC1_FLITS Number of ?its to come into the Receive Response
FIFO from the network.
GM_ORB_PERF_VC1_PKTS Number of packets to come into the Receive
Response FIFO from the network.
GM_ORB_PERF_VC1_STALLED Number of packets not given access to the RX
Control Logic because there is not enough credits
available from the RAT.
18 S–0025–10Overview of Gemini Hardware Counters
Table 8. RAT Performance Counters
Name Description
GM_RAT_PERF_COUNTER_EN Enables the performance counters.
GM_RAT_PERF_DATA_FLITS_VC0 Number of data ?its received on VC0 (request
pipeline).
GM_RAT_PERF_DATA_FLITS_VC1 Number of data ?its received on VC1 (request
pipeline).
GM_RAT_PERF_HEADER_FLITS_VC0 Number of header ?its received on VC0 (request
pipeline).
GM_RAT_PERF_HEADER_FLITS_VC1 Number of header ?its received on VC1 (request
pipeline).
GM_RAT_PERF_STALLED_CREDITS_VC0 Number of cycles VC0 (request pipeline) is stalled
due to insuf?cient credits.
GM_RAT_PERF_STALLED_CREDITS_VC1 Number of cycles VC1 (request pipeline) is stalled
due to insuf?cient credits.
GM_RAT_PERF_STALLED_TRANSLATION_VC0 Number of cycles VC0 (request pipeline) is stalled
due to unavailable translation data.
GM_RAT_PERF_STALLED_TRANSLATION_VC1 Number of cycles VC1 (request pipeline) is stalled
due to unavailable translation data.
GM_RAT_PERF_TRANSLATION_ERRORS_VC0 Number of translation errors seen on VC0 (request
pipeline).
GM_RAT_PERF_TRANSLATION_ERRORS_VC1 Number of translation errors seen on VC1 (request
pipeline).
GM_RAT_PERF_TRANSLATIONS_VC0 Number of translations requested on VC0 (request
pipeline).
GM_RAT_PERF_TRANSLATIONS_VC1 Number of translations requested on VC1 (request
pipeline).
S–0025–10 19Using the Cray Gemini Hardware Counters
Table 9. RMT Performance Counters
Name Description
GM_RMT_PERF_PUT_BYTES_RX Tally of bytes received in all PUT packets that had
the RMT Enable ?eld set that entered and exited the
RMT with OK status.
GM_RMT_PERF_PUT_CAM_EVIT PUT sequences evicted from the CAM.
GM_RMT_PERF_PUT_CAM_FILL New PUT sequence packet arrived and successfully
allocated in the CAM.
GM_RMT_PERF_PUT_CAM_HITS Packet for PUT sequence currently stored in RMT
arrived and successfully located entry in CAM.
GM_RMT_PERF_PUT_CAM_MISS New PUT sequence packet arrived, but did not
allocate because CAM was full.
GM_RMT_PERF_PUT_PARITY Number of sequences evicted from CAM due to
uncorrectable parity errors.
GM_RMT_PERF_PUT_RECV_COMPLETE Number of MsgRcvComplete packets received
which evicted a CAM entry.
GM_RMT_PERF_PUT_TIMEOUTS Number of sequences evicted from CAM due to
timeout.
GM_RMT_PERF_SEND_BYTES_RX Tally of bytes received in all SEND packets that had
the RMT Enable ?eld set and entered and exited the
RMT with OK status.
GM_RMT_PERF_SEND_CAM_EVIT SEND sequences evicted from the CAM.
GM_RMT_PERF_SEND_CAM_FILL New SEND sequence packet arrived and
successfully allocated in the CAM.
GM_RMT_PERF_SEND_CAM_HITS Packet for SEND sequence currently stored in RMT
arrived and successfully located entry in CAM.
GM_RMT_PERF_SEND_CAM_MISS New SEND sequence packet arrived, but did not
allocate because CAM was full.
GM_RMT_PERF_SEND_PARITY Number of sequences evicted from CAM due to
uncorrectable parity errors.
GM_RMT_PERF_SEND_ABORTS Number of SEND sequences that were aborted.
GM_RMT_PERF_SEND_TIMEOUTS Number of sequences evicted from CAM due to
timeout.
20 S–0025–10Overview of Gemini Hardware Counters
Table 10. SSID Performance Counters
Name Description
GM_SSID_PERF_COMPLETION_COUNT_1 Provides a count of completed request packet
sequences. The type of sequence completions
counted by this register is controlled by the
SSID Performance – Completion Count
Selector Register.
GM_SSID_PERF_COMPLETION_COUNT_2 Provides a count of completed request packet
sequences. The type of sequence completions
counted by this register is controlled by the
SSID Performance – Completion Count
Selector Register.
GM_SSID_PERF_COMPLETION_COUNT_SELECTOR Speci?es the types of completion events
that are counted in the SSID Performance
– Completion Count 1 Register (bits 3-0)
and the SSID Performance – Completion
Count 2 Register (bits 11-8). See the table of
SSID_PerfCompletionCountSelect Encoding
values for encoding of these ?elds.
GM_SSID_PERF_OUT_STALLED_DURATION The accumulated number of cycles of cclk for
which the SSID had a valid ?it available to
send to the ORB but sending of the ?it had
to be stalled while waiting for a credit from
the ORB. This value is cleared by writing any
value to this register.
GM_SSID_PERF_OUTOFSSIDS_COUNT The number of Allocate SSID requests that
have been received for which processing of
the request had to be stalled for one or more
clock cycles because a free SSID was not
immediately available to service the request.
This value is cleared by writing any value to
this register.
GM_SSID_PERF_OUTOFSSIDS_DURATION The accumulated number of cycles of cclk for
which processing of Allocate SSID requests
has been stalled because a free SSID is not
available to service the request. This value is
cleared by writing any value to this register.
S–0025–10 21Using the Cray Gemini Hardware Counters
Name Description
GM_SSID_PERF_SSID_ALLOCATE_COUNT The total number of Allocate SSID requests
that have been received, across all channels
(all FMA descriptors and all BTE VCs),
because this register was last cleared, and that
resulted in a SSID actually being allocated.
Allocate SSID requests that do not result
in a SSID being allocated (i.e. redundant
Allocate requests) are not counted. This value
is cleared by writing any value to this register.
GM_SSID_PERF_SSIDS_IN_USE Bits 7-0 specify the number of SSIDs
currently in use across all Request Channels.
This value is not affected by writes to this
register. This ?eld is initialized to its reset
value by a full reset and by an ht reset.
Bits 23-16 specify the maximum number of
SSIDs that have been in use simultaneously,
across all channels (all FMA descriptors
and all BTE Vcs), since this register was
last initialized. This value is initialized to
CurrentSSIDsInUse by writing any
value to this register. This ?eld is initialized
to its reset value by a full reset.
Table 11. Transmit Arbiter Performance Counters
Name Description
GM_TARB_PERF_BTE_BLOCKED Transmit Arbiter (TARB) Performance BTE
Blocked Count
GM_TARB_PERF_BTE_FLITS TARB Performance BTE Flit Count
GM_TARB_PERF_BTE_PKTS TARB Performance BTE Packet Count
GM_TARB_PERF_BTE_STALLED TARB Performance BTE Stalled Count
GM_TARB_PERF_FMA_BLOCKED TARB Performance FMA Blocked Count
GM_TARB_PERF_FMA_FLITS TARB Performance FMA Flit Count
GM_TARB_PERF_FMA_PKTS TARB Performance FMA Packet Count
GM_TARB_PERF_FMA_STALLED TARB Performance FMA Stalled Count
GM_TARB_PERF_LB_BLOCKED TARB Performance LB Blocked Count
GM_TARB_PERF_LB_FLITS TARB Performance LB Flit Count
GM_TARB_PERF_LB_PKTS TARB Performance LB Packet Count
22 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_TARB_PERF_LB_STALLED TARB Performance LB Stalled Count
GM_TARB_PERF_OUT_FLITS TARB Performance Output Flit Count
GM_TARB_PERF_OUT_PKTS TARB Performance Output Packet Count
GM_TARB_PERF_OUT_STALLED TARB Performance Output Stalled Count
1.3 Gemini Tile MMRs
The Gemini network consists of 48 tiles, arranged in 6 rows of 8 columns. Within
each tile there are memory-mapped registers associated with the LCB and with the
rest of the tile. The local block has shared connections to each row of tiles.
By default, when only the name of the MMR is used, an event is counted on all 48
tiles. To address an individual tile, append the row (0-5) and column (0-7) to the
name, as shown in the table.
Table 12. Description of Gemini Tile MMRs
Name Description
GM_TILE_PERF_VC0_PHIT_CNT:n:m Number of vc0 phits read from inq buffer
GM_TILE_PERF_VC1_PHIT_CNT:n:m Number of vc1 phits read from inq buffer
GM_TILE_PERF_VC0_PKT_CNT:n:m Number of vc0 packets read from inq buffer
GM_TILE_PERF_VC10_PKT_CNT:n:m Number of vc1 packets read from inq buffer
GM_TILE_PERF_INQ_STALL:n:m Number of clock periods a valid reference is blocked
from the routing pipeline.
GM_TILE_PERF_CREDIT_STALL:n:m Number of clock periods a valid reference is stalled in
the column buffers, waiting on transmissions credits.
S–0025–10 23Using the Cray Gemini Hardware Counters
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permitted by contract or by written permission of Cray Inc.
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Version 1.0 Published July 2010 Supports CrayPat release 5.1 and CLE release 3.1 running on Cray XT systems.
24 S–0025–10
Overview of Gemini Hardware Counters
This document describes the Gemini Performance Counters and how to use them to
optimize individual applications and system traf?c.
Send e-mail to docs@cray.com with any comments that will help us to improve the
accuracy and usability of this document. Be sure to include the title and number
of the document with your comments. We value your comments and will respond
to them promptly.
Accessing network performance counters is desirable for application developers,
system library developers (e.g. MPI), and system administrators. Application
developers want to improve their application run-times or measure what affect other
traf?c on the system has on their application. System library developers want to
optimize their collective operations. System Administrators want to observe the
system, looking for hotspots. Effective with the CrayPat (Cray performance analysis
tool) version 5.1 and Cray Linux Environment (CLE) version 3.1 software releases
for the Cray XE platform, users can monitor many of the performance counters that
reside on the Gemini networking chip.
There are two categories of Gemini performance counters available to users. NIC
performance counters record information about the data moving through theNetwork
Interface Controller (NIC). On the Gemini ASIC there are two NICs, each attached
to a compute node. Thus, the data from the NIC performance counters re?ects
network transfers beginning and ending on the node. These performance counters
are read-only.
Network router tile counters are available on a per-Gemini basis. There are both
read-only and read/write tile counters. Each chip has 48 router tiles, arranged in a
6x8 grid. Eight processor tiles connect to each of the two Gemini NICs. Each NIC
connects to a different node, running separate Linux instances.
If collection at other points of the application is desired, use the CrayPat API to
insert regions as described in the pat_build man page. It is recommended that
you do not collect any other performance data when collecting network counters.
Data collection of network counters is much more expensive than other performance
data collection, and will skew other results. At the time the instrumented executable
program is launched with the aprun command, a set of environment variables,
PAT_RT_NWPC_*, provide access to the Gemini network performance counters.
These environment variables are described in the intro_craypat man page.
S–0025–10 1Using the Cray Gemini Hardware Counters
1.1 Using CrayPat to Monitor Gemini Counters
The CrayPat utility pat_build instruments an executable ?le. One aspect of the
instrumentation includes intercepting entries into and returns out of a function. This
is known formally as tracing. Information such as time stamps and performance
counter values are recorded at this time.
CrayPat supports instrumentation of an application binary for collection of Gemini
counters. Counter values are recorded at application runtime, and are presented to the
user through a table generated by pat_report. The CrayPat user interface to request
instrumentation is similar to that for processor performance counters. There is no
Gemini counter display available in Cray Apprentice2 at this time. A new display will
be available in a subsequent release of the Cray Apprentice2 software.
Although the user interface to request network counters is similar to processor
counters, there are some signi?cant differences that must be understood. Depending
on the type of counters requested, some are shared across all processors within a
node, some are shared between two nodes and some are shared across all applications
passing through a chip. Some counters monitor all traf?c for your application, even
on nodes that are not reserved for your application, and some monitor locally, that is
they monitor only traf?c associated with nodes assigned to a Gemini chip and no
other traf?c from the network.
Users should also be aware that access to the network counters is more
resource-intensive than access to the processor performance counters. Because
Gemini counters are a shared resource, the system software is designed to provide
dedicated access whenever possible. This is done through the Application Level
Placement Scheduler (ALPS) by ensuring that an application collecting counters is
not placed on the same Gemini chip as another application collecting performance
counters. It does not prevent a second application from being placed on the same
Gemini chip that is not collecting counters however. This compromise assures better
system utilization because compute nodes are not left unavailable for use by another
application.
The CrayPat 5.1 release focuses on the use of the NIC and ORB counters available
within the Gemini chip. The values collected from these counters are local to a
node and therefore speci?c to an application. Traf?c between MPI ranks cannot be
distinguished through the counters. The event names that CrayPat supports are listed
at the end of this document. Network counters are only collected for the MAIN
thread. Values are collected at the beginning and end of the instrumented application.
Instrumentation overhead is minimal. This gives a high-level view of the program's
use of the networking router in terms of the counters speci?ed. Currently the time to
access counter data is too expensive to collect more frequently. A future release of
CLE will address these performance limitations.
2 S–0025–10Overview of Gemini Hardware Counters
Before attempting the following examples verify that your system has a Gemini
network:
$ module list
xtpe-network-gemini
Attempting to collect Gemini performance counters on a system that does not have
the Gemini network will result in a fatal error:
$ aprun -n 16 my_program+pat
CrayPat/X: Version 5.1 Revision 3329 05/20/10 11:26:16
pat[FATAL][0]: initialization of NW performance counter API failed
[No such file or directory]
Example 1. Collect stalls associated with node traf?c to and from the network
This example enables tracing of MAIN.
$ pat_build -w my_program
$ export PAT_RT_NWPC=GM_ORB_PERF_VC0_STALLED,GM_ORB_PERF_VC1_STALLED
$ aprun my_program+pat
Example 2. Display network counter data
$ pat_report my_program+pat+11171-41tdot.xf> counter_rpt
Example output from pat_report:
NWPC Data by Function Group and Function Group / Function / Node Id=0='HIDE'
=====================================================================
Total
---------------------------------------------------------------------
Time% 100.0%
Time 2.476423 secs
GM_ORB_PERF_VC1_STALLED 0
GM_ORB_PERF_VC1_BLOCKED 0
GM_ORB_PERF_VC1_BLOCKED_PKT_GEN 0
GM_ORB_PERF_VC1_PKTS 48
GM_ORB_PERF_VC1_FLITS 48
GM_ORB_PERF_VC0_STALLED 111
GM_ORB_PERF_VC0_PKTS 48
GM_ORB_PERF_VC0_FLITS 201
=====================================================================
S–0025–10 3Using the Cray Gemini Hardware Counters
Example 3. Collect data for a custom group of network counters
In this example a user creates a group of network events in a ?le called
my_nwpc_groups, one called 1 and the other called CQ_AMO:
$ cat my_nwpc_groups
# Group 1: Outstanding Request Buffer
1 =
GM_ORB_PERF_VC1_STALLED,
GM_ORB_PERF_VC1_BLOCKED,
GM_ORB_PERF_VC1_BLOCKED_PKT_GEN,
GM_ORB_PERF_VC1_PKTS,
GM_ORB_PERF_VC1_FLITS,
GM_ORB_PERF_VC0_STALLED,
GM_ORB_PERF_VC0_PKTS,
GM_ORB_PERF_VC0_FLITS
# Group CQ_AMO:
CQ_AMO =
GM_AMO_PERF_COUNTER_EN,
GM_AMO_PERF_CQ_FLIT_CNTR,
GM_AMO_PERF_CQ_PKT_CNTR,
GM_AMO_PERF_CQ_STALLED_CNTR,
GM_AMO_PERF_CQ_BLOCKED_CNTR
$ pat_build -w my_program
$ export PAT_RT_NWPC_FILE=my_nwpc_groups
$ export PAT_RT_NWPC=1,CQ_AMO
$ aprun -n16 my_program+pat
4 S–0025–10Overview of Gemini Hardware Counters
Example output from pat_report:
NWPC Data by Function Group and Function
Group / Function / Node Id=0='HIDE'
=====================================================================
Total
---------------------------------------------------------------------
Time% 100.0%
Time 2.639046 secs
GM_ORB_PERF_VC1_STALLED 72525
GM_ORB_PERF_VC1_PKTS 50457
GM_AMO_PERF_COUNTER_EN 0
GM_AMO_PERF_CQ_FLIT_CNTR 11752
GM_AMO_PERF_CQ_PKT_CNTR 5876
GM_AMO_PERF_CQ_STALLED_CNTR 5092
GM_AMO_PERF_CQ_BLOCKED_CNTR 29
=====================================================================
Example 4. Suppress instrumented entry points from recording performance
data to reduce overhead
This example assumes a NWPC group FMAS exists and is available for use. Because
the program is traced, the PAT_RT_TRACE_FUNCTION_NAME is set to suppress
any data collection by already instrumented entry points in my_program+pat. This
means that NWPC values will only be recorded for the MAIN thread at the start and
the end of the instrumented program. Instrumentation overhead is minimal.
$ pat_build -u -g mpi my_program
$ export PAT_RT_NWPC=FMAS
$ export PAT_RT_TRACE_FUNCITON_NAME=*:0
$ aprun -n32 my_program+pat
This gives a high-level view of the program's use of the networking router in terms of
what the FMAS group describes. If more details about NWPC use during execution
of the program are desired, the PAT_RT_TRACE_FUNCTION_NAME environment
variable need not be set, but the signi?cant overhead injected by reading the NWPCs
may make the resulting performance data inaccurate.
To selectively collect NWPCs and the other performance data for traced functions,
add them to the end of PAT_RT_TRACE_FUNCTION_NAME:
$ export PAT_RT_TRACE_FUNCTION_NAME=0:*,mxm,MPI_Bcast
S–0025–10 5Using the Cray Gemini Hardware Counters
1.2 Gemini NIC Counters
To better understand how to use the NIC counters, you need to understand some of
the terminology speci?c to the Gemini network architecture.
The Block Transfer Engine (BTE)
A Gemini network packet typically consists of one or more ?its, which are the units
of ?ow control for the network. Because ?its are usually larger than the physical
datapath, they are divided into phits, which are the units of data that the network can
handle physically. A packet must contain at least two phits, one for the header and
one for the cyclical redundancy check (CRC).
The V0 counters support the request channel and the V1 counters support the
response channel. A ?it/pkt ratio can tell the user if the data entering the network was
not aligned, eg a ratio greater than 1 indicates misaligned data is being sent across
the network. Because there is a bandwidth/pipe size difference between outgoing
and incoming (outgoing is smaller), in general you will notice more stalls on the V0
(request) channel.
The following counters are recommended as a way to begin using the Gemini NWPC:
GM_ORB_PERF_VC0_STALLED
GM_ORB_PERF_VC1_STALLED
GM_ORB_PERF_VC0_PKTS
GM_ORB_PERF_VC1_PKTS
GM_ORB_PERF_VC0_FLITS
GM_ORB_PERF_VC1_FLITS
Table 1. Atomic Memory Operations Performance Counters
Name Description
GM_AMO_PERF_ACP_COMP_CNTR Number of Atomic Memory Operation (AMO)
computations that have occurred.
GM_AMO_PERF_ACP_MEM_UPDATE_CNTR Number of AMO logic cache write-throughs that
have occurred.
GM_AMO_PERF_ACP_STALL_CNTR Number of AMO logic pipeline stalls that have
occurred.
GM_AMO_PERF_AMO_HEADER_CNTR Number of request headers processed by
the Decode Logic that have had an AMO
computation. Error packets are not counted.
GM_AMO_PERF_COUNTER_EN When set, counting is enabled. When cleared,
counting is disabled.
GM_AMO_PERF_CQ_BLOCKED_CNTR Number of cycles the CQ FIFO is blocked.
6 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_AMO_PERF_CQ_FLIT_CNTR Number of ?its (network ?ow control units) that
are read from the CQ FIFO.
GM_AMO_PERF_CQ_PKT_CNTR Number of packets that are read from the CQ
FIFO.
GM_AMO_PERF_CQ_STALLED_CNTR Number of cycles the CQ FIFO is stalled.
GM_AMO_PERF_DONE_INV_CNTR Number of times a valid cache entry was
invalidated because there were no more
outstanding AMO requests targeting it and the last
request did not have the cacheable bit set.
GM_AMO_PERF_ERROR_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had errors.
GM_AMO_PERF_FLUSH_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had a Flush command.
Error packets are not counted.
GM_AMO_PERF_FULL_INV_CNTR Number of times a valid but inactive cache entry
was invalidated to make room for a new AMO
address. A high value in this counter indicates that
there are too many cacheable AMO addresses and
that the cache is being thrashed.
GM_AMO_PERF_GET_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had an GET command.
Error packets are not counted.
GM_AMO_PERF_MSGCOMP_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had a MsgComplete
command. Error packets are not counted.
GM_AMO_PERF_PUT_HEADER_CNTR Number of request headers processed by the
Decode Logic that have had an PUT command.
Error packets are not counted.
GM_AMO_PERF_REQLIST_FULL_STALL_CNTR Number of times an AMO request causes the NRP
to stall waiting for a Request List entry to become
free.
GM_AMO_PERF_RMT_BLOCKED_CNTR Number cycles the RMT FIFO is blocked
GM_AMO_PERF_RMT_FLIT_CNTR Number of ?its that are read from the RMT FIFO
GM_AMO_PERF_RMT_PKT_CNTR Number of packets that are read from the RMT
FIFO
GM_AMO_PERF_RMT_STALLED_CNTR Number cycles the RMT FIFO is stalled
S–0025–10 7Using the Cray Gemini Hardware Counters
Name Description
GM_AMO_PERF_TAG_HIT_CNTR Number of AMO requests that have been
processed in the Tag Store and have resulted in a
cache hit.
GM_AMO_PERF_TAG_MISS_CNTR Number of AMO requests that have been
processed in the Tag Store and have resulted in a
cache miss.
GM_AMO_PERF_TAG_STALL_CNTR Number of times a GET/PUT request hits in the
cache and causes the NRP to stall.
Table 2. Fast Memory Access Performance Counters
Name Description
GM_FMA_PERF_CQ_PKT_CNT Number of packets from Fast Memory Access
(FMA) to CQ.
GM_FMA_PERF_CQ_STALLED_CNT Number of clock cycles FMA_CQ was stalled due to
lack of credits.
GM_FMA_PERF_HT_NP_REQ_FLIT_CNT Number of HT NP request ?its to FMA.
GM_FMA_PERF_HT_NP_REQ_PKT_CNT Number of HT NP request packets to FMA.
GM_FMA_PERF_HT_P_REQ_FLIT_CNT Number of HT P request ?its to FMA.
GM_FMA_PERF_HT_P_REQ_PKT_CNT Number of HT P request packets to FMA.
GM_FMA_PERF_HT_RSP_PKT_CNT Number of HT response packets from FMA to HT.
GM_FMA_PERF_HT_RSP_STALLED_CNT Number of clock cycles FMA_HT_RSP was stalled
due to lack of credits.
GM_FMA_PERF_TARB_FLIT_CNT Number of ?its from FMA to TARB.
GM_FMA_PERF_TARB_PKT_CNT Number of packets from FMA to TARB.
GM_FMA_PERF_TARB_STALLED_CNT Number of clock cycles FMA_TARB was stalled
due to lack of credits.
8 S–0025–10Overview of Gemini Hardware Counters
Table 3. Hyper-transport Arbiter Performance Counters
Name Description
GM_HARB_PERF_AMO_NP_BLOCKED Number of times AMO Non-Posted Queue has an
entry, but is blocked from using the Non-Posted
Initiator Request output channel by the BTE
Non-Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_NP_FLITS Number of ?its coming out of the AMO Non-Posted
Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_NP_PKTS Number of packets coming out of the AMO
Non-Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_NP_STALLED Number of cycles the AMO Non-Posted Queue
is stalled due to a lack credits on the Non-Posted
Initiator Request channel. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_ACP_BLOCKED Number of times AMO Posted AMO Computation
Pipe Queue has an entry, but is blocked from
using the Posted Initiator Request output channel
by another Posted Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_ACP_FLITS Number of ?its coming out of the AMO Posted
AMO Computation Pipe Queue. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
S–0025–10 9Using the Cray Gemini Hardware Counters
Name Description
GM_HARB_PERF_AMO_P_ACP_PKTS Number of packets coming out of the AMO Posted
AMO Computation Pipe Queue. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_ACP_STALLED Number of cycles the AMO Posted AMO
Computation Pipe Queue is stalled due to a lack
credits on the Posted Initiator Request channel.
The Local Block has read/write access to the full
counter. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_BLOCKED Number of times AMO Posted New Request Pipe
Queue has an entry, but is blocked from using the
Posted Initiator Request output channel by another
Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_FLITS Number of ?its coming out of the AMO Posted
New Request Pipe Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_PKTS Number of packets coming out of the AMO Posted
New Request Pipe Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_AMO_P_NRP_STALLED Number of cycles the AMO Posted New Request
Pipe Queue is stalled due to a lack credits on the
Posted Initiator Request channel. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
10 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_HARB_PERF_BTE_NP_BLOCKED Number of times AMO Non-Posted BTE Queue has
an entry, but is blocked from using the Non-Posted
Initiator Request output channel by another
Non-Posted Queue. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_NP_FLITS Number of ?its coming out of the AMO Non-Posted
BTE Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_NP_PKTS Number of packets coming out of the AMO
Non-Posted BTE Queue. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_NP_STALLED Number of cycles the AMO Non-Posted BTE Queue
is stalled due to a lack credits on the Posted Initiator
Request channel. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_P_BLOCKED Number of times AMO Posted BTE Queue has an
entry, but is blocked from using the Posted Initiator
Request output channel by another Posted Queue.
The Local Block has read/write access to the full
counter. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_BTE_P_FLITS Number of ?its coming out of the AMO Posted
BTE Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
S–0025–10 11Using the Cray Gemini Hardware Counters
Name Description
GM_HARB_PERF_BTE_P_PKTS Number of packets coming out of the AMO Posted
BTE Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_BTE_P_STALLED Number of cycles the AMO Posted BTE Queue is
stalled due to a lack credits on the Posted Initiator
Request channel. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
GM_HARB_PERF_COUNTER_EN When set, counting is enabled. When clear, counting
is disabled. This MMR is reset by the chip reset
(i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_NP_FLITS Number of ?its on the non-posted initiator request
output of the HARB block. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_IREQ_NP_PKTS Number of packets on the non-posted initiator
request output of the HARB Block. The Local Block
has read/write access to the full counter. Bits 63:48
of this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_NP_STALLED Number of cycles on the non-posted initiator request
output of the HARB is stalled due to a lack credits
on the Non-Posted Initiator Request channel. The
Local Block has read/write access to the full counter.
Bits 63:48 of this MMR are unimplemented and
always return zero. This MMR is reset to all zeros
by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
12 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_HARB_PERF_IREQ_P_FLITS Number of ?its on the posted initiator request output
of the HARB block. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. Bits
63:48 of this MMR are unimplemented and always
return zero. This MMR is reset to all zeros by the
chip reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_P_PKTS Number of packets on the posted initiator request
output of the HARB Block. The Local Block has
read/write access to the full counter. Bits 63:48 of
this MMR are unimplemented and always return
zero. This MMR is reset to all zeros by the chip
reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_IREQ_P_STALLED Number of cycles on the posted initiator request
output of the HARB is stalled due to a lack credits
on the Posted Initiator Request channel. The Local
Block has read/write access to the full counter. Bits
63:48 of this MMR are unimplemented and always
return zero. This MMR is reset to all zeros by the
chip reset (i_reset), but not by HT reset (i_ht_reset).
GM_HARB_PERF_RAT_P_BLOCKED Number of times AMO Posted RAT Queue has an
entry, but is blocked from using the Posted Initiator
Request output channel by another Posted Queue.
The Local Block has read/write access to the full
counter. Bits 63:48 of this MMR are unimplemented
and always return zero. This MMR is reset to all
zeros by the chip reset (i_reset), but not by HT reset
(i_ht_reset).
GM_HARB_PERF_RAT_P_FLITS Number of ?its coming out of the AMO Posted
RAT Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
S–0025–10 13Using the Cray Gemini Hardware Counters
Name Description
GM_HARB_PERF_RAT_P_PKTS Number of packets coming out of the AMO Posted
RAT Queue. The Local Block has read/write access
to the full counter. Bits 63:48 of this MMR are
unimplemented and always return zero. This MMR
is reset to all zeros by the chip reset (i_reset), but not
by HT reset (i_ht_reset).
GM_HARB_PERF_RAT_P_STALLED Number of cycles the AMO Posted RAT Queue is
stalled due to a lack credits on the Posted Initiator
Request channel. The Local Block has read/write
access to the full counter. Bits 63:48 of this MMR
are unimplemented and always return zero. This
MMR is reset to all zeros by the chip reset (i_reset),
but not by HT reset (i_ht_reset).
Table 4. Network Address Translation Performance Counters
Name Description
GM_NAT_PERF_BTE_BLOCKED Number of cycles a BTE translation is blocked due
to arbitration loss.
GM_NAT_PERF_BTE_STALLED Number of cycles a BTE translation is stalled due to
MMR access.
GM_NAT_PERF_BTE_TRANSLATIONS Number of translations performed for the BTE
interface.
GM_NAT_PERF_COUNTER_EN When set, counting is enabled. When cleared,
counting is disabled.
GM_NAT_PERF_REQ_BLOCKED Number of cycles a REQ translation is blocked due
to arbitration loss.
GM_NAT_PERF_REQ_STALLED Number of cycles a REQ translation is stalled due to
MMR access.
GM_NAT_PERF_REQ_TRANSLATIONS Number of translations performed for the REQ
interface.
GM_NAT_PERF_RSP_BLOCKED Number of cycles a RSP translation is blocked due
to arbitration loss.
GM_NAT_PERF_RSP_STALLED Number of cycles a RSP translation is stalled due to
MMR access.
GM_NAT_PERF_RSP_TRANSLATIONS Number of translations performed for the RSP
interface.
GM_NAT_PERF_TRANS_ERROR0 Number of translations that failed due to error 0
(Uncorrectable error in translation).
14 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_NAT_PERF_TRANS_ERROR1 Number of translations that failed due to error 1
(VMDH table invalid entry).
GM_NAT_PERF_TRANS_ERROR2 Number of translations that failed due to error 2
(MDDT/MRT invalid or illegal entry).
GM_NAT_PERF_TRANS_ERROR3 Number of translations that failed due to error 3
(Protection tag violation).
GM_NAT_PERF_TRANS_ERROR4 Number of translations that failed due to error 4
(memory bounds error).
GM_NAT_PERF_TRANS_ERROR5 Number of translations that failed due to error 5
(write permission error)
Table 5. Netlink Performance Counters
Name Description
GM_NL_PERF_ALL_LCBS_REQS_TO_NIC_0_STALLED Number of ticks all LCBs requests have
stalled to NIC 0.
GM_NL_PERF_ALL_LCBS_REQS_TO_NIC_1_STALLED Number of ticks all LCBs requests have
stalled to NIC 1.
GM_NL_PERF_ALL_LCBS_RSP_TO_NIC_0_STALLED Number of ticks all LCBs responses have
stalled to NIC 0.
GM_NL_PERF_ALL_LCBS_RSP_TO_NIC_1_STALLED Number of ticks all LCBs responses have
stalled to NIC 1.
GM_NL_PERF_CNTRL Controls the performance counters.
Writing a 1 to the Start ?eld starts the
counters. Writing a 1 to the Stop ?eld
stops the counters. Writing a 1 to the
Clear ?eld clears the counters.
GM_NL_PERF_LCB_n_REQ_CMP_22 Decompressed request data to two phit
LCB_n, where n is a value from 0 to 7
that speci?es the LCB.
GM_NL_PERF_LCB_n_REQ_CMP_44 Decompressed request data to one phit
LCB_n, where n is a value from 0 to 7
that speci?es the LCB.
GM_NL_PERF_LCB_n_REQ_TO_NIC_0 Number of requests from LCB_n to NIC
0.
GM_NL_PERF_LCB_n_REQ_TO_NIC_0_STALLED Number of ticks LCB_n requests are
blocked to NIC 0.
GM_NL_PERF_LCB_n_REQ_TO_NIC_1 Number of requests from LCB_n to NIC
1.
S–0025–10 15Using the Cray Gemini Hardware Counters
Name Description
GM_NL_PERF_LCB_n_REQ_TO_NIC_1_STALLED Number of ticks LCB_n requests are
blocked to NIC 1.
GM_NL_PERF_LCB_n_REQ_TO_PHITS Number of request phits received on
LCB_n.
GM_NL_PERF_LCB_n_REQ_TO_PKTS Number of request packets received on
LCB_n.
GM_NL_PERF_LCB_n_RSP_CMP_22 Decompressed response data to two phit
LCB_n
GM_NL_PERF_LCB_n_RSP_TO_NIC_1 Number of responses from LCB_n to
NIC 1.
GM_NL_PERF_LCB_n_RSP_TO_NIC_1_STALLED Number of ticks LCB_n responses are
blocked to NIC 1.
GM_NL_PERF_NIC_0_REQ_STALLED_TO_ALL_LCBS Number of ticks NIC_0 requests are
blocked to all LCBs.
GM_NL_PERF_NIC_0_REQ_TO_LCB_n Number of requests from NIC_0 LCB_
n.
GM_NL_PERF_NIC_0_REQ_TO_LCB_n_STALLED Number of ticks NIC_0 requests are
blocked to LCB_n.
GM_NL_PERF_NIC_0_RSP_STALLED_TO_ALL_LCBS Number of ticks NIC_0 responses are
blocked to all LCBs.
GM_NL_PERF_NIC_0_RSP_TO_LCB_n Number of responses from NIC_0 LCB_
n.
GM_NL_PERF_NIC_0_RSP_TO_LCB_n_STALLED Number of ticks NIC_0 responses are
blocked to LCB_n.
GM_NL_PERF_NIC_1_REQ_STALLED_TO_ALL_LCBS Number of ticks NIC_0 requests are
blocked to all LCBs.
GM_NL_PERF_NIC_1_REQ_TO_LCB_n Number of requests from NIC_1 to
LCB_ n.
GM_NL_PERF_NIC_1_REQ_TO_LCBn_STALLED Number of ticks NIC_1 requests are
blocked to LCB_n.
GM_NL_PERF_NIC_1_RSP_STALLED_TO_ALL_LCBS Number of ticks NIC_1 responses are
blocked to all LCBs.
GM_NL_PERF_NIC_1_RSP_TO_LCB_n Number of responses from NIC_1 LCB_
n.
GM_NL_PERF_NIC_1_RSP_TO_LCB_n_STALLED Number of ticks NIC_1 responses are
blocked to LCB_n.
16 S–0025–10Overview of Gemini Hardware Counters
Table 6. NPT Performance Counters
Name Description
GM_NPT_PERF_ACP_BLOCKED_CNTR Number of cycles the ACP FIFO is blocked.
GM_NPT_PERF_ACP_FLIT_CNTR Number of ?its that are read from the ACP FIFO.
GM_NPT_PERF_ACP_PKT_CNTR Number of packets that are read from the ACP
FIFO.
GM_NPT_PERF_ACP_STALLED_CNTR Number of cycles the ACP FIFO is stalled.
GM_NPT_PERF_BTE_RSP_PKT_CNTR Number of packets that are sent to the Netlink as Get
or Flush responses.
GM_NPT_PERF_COUNTER_EN Provides the count enable.
GM_NPT_PERF_FILL_RSP_PKT_CNTR Number of packets that are sent to the AMO block
as ?ll responses.
GM_NPT_PERF_HTIRSP_ERR_CNTR Number of packets that are received from the HT
cave and have an error status.
GM_NPT_PERF_HTIRSP_FLIT_CNTR Number of ?its that are received from the HT cave.
GM_NPT_PERF_HTIRSP_PKT_CNTR Number of packets that are received from the HT
cave.
GM_NPT_PERF_LB_BLOCKED_CNTR Number of cycles the LB FIFO is blocked.
GM_NPT_PERF_LB_FLIT_CNTR Number of ?its that are read from the LB FIFO.
GM_NPT_PERF_LB_PKT_CNTR Number of packets that are read from the LB FIFO.
GM_NPT_PERF_LB_STALLED_CNTR Number of cycles the LB FIFO is stalled.
GM_NPT_PERF_NL_RSP_PKT_CNTR Number of packets that are sent to the AMO block
as ?ll responses.
GM_NPT_PERF_NPT_BLOCKED_CNTR Number of cycles the NPT FIFO is blocked.
GM_NPT_PERF_NPT_FLIT_CNTR Number of ?its that are read from the NPT FIFO.
GM_NPT_PERF_NPT_PKT_CNTR Number of packets that are read from the NPT FIFO.
GM_NPT_PERF_NPT_STALLED_CNTR Number of cycles the NPT FIFO is stalled.
GM_NPT_PERF_NRP_BLOCKED_CNTR Number of cycles the NRP FIFO is blocked.
GM_NPT_PERF_NRP_FLIT_CNTR Number of ?its that are read from the NRP FIFO.
GM_NPT_PERF_NRP_PKT_CNTR Number of packets that are read from the NRP
FIFO.
GM_NPT_PERF_NRP_STALLED_CNTR Number of cycles the NRP FIFO is stalled.
S–0025–10 17Using the Cray Gemini Hardware Counters
Table 7. ORB Performance Counters
Name Description
GM_ORB_PERF_VC0_FLITS Number of ?its to come into the TX Input Queue
from the SSID.
GM_ORB_PERF_VC0_PKTS Number of packets to come into the TX Input Queue
from the SSID.
GM_ORB_PERF_VC0_STALLED Number of packets not given access to the TX
Control Logic because there is not enough credits
available from the NL Block, or there are no
available memory locations from the ORD RAM,
or a tail ?it has not been received in the ORB Input
Queue when performing store-and-forward.
GM_ORB_PERF_VC1_BLOCKED Number of packets not given access to the RX
Control Logic because the read address and write
address into the ORD RAM are attempting to access
the same bank of the ORD RAM or because there
is a read access to the ORD RAM from the Local
Block.
GM_ORB_PERF_VC1_BLOCKED_PKT_GEN Number of times the RX Response FIFO is blocked
because a packet in the RX Control Logic is being
translated into the format used by the rest of the
NIC.
GM_ORB_PERF_VC1_FLITS Number of ?its to come into the Receive Response
FIFO from the network.
GM_ORB_PERF_VC1_PKTS Number of packets to come into the Receive
Response FIFO from the network.
GM_ORB_PERF_VC1_STALLED Number of packets not given access to the RX
Control Logic because there is not enough credits
available from the RAT.
18 S–0025–10Overview of Gemini Hardware Counters
Table 8. RAT Performance Counters
Name Description
GM_RAT_PERF_COUNTER_EN Enables the performance counters.
GM_RAT_PERF_DATA_FLITS_VC0 Number of data ?its received on VC0 (request
pipeline).
GM_RAT_PERF_DATA_FLITS_VC1 Number of data ?its received on VC1 (request
pipeline).
GM_RAT_PERF_HEADER_FLITS_VC0 Number of header ?its received on VC0 (request
pipeline).
GM_RAT_PERF_HEADER_FLITS_VC1 Number of header ?its received on VC1 (request
pipeline).
GM_RAT_PERF_STALLED_CREDITS_VC0 Number of cycles VC0 (request pipeline) is stalled
due to insuf?cient credits.
GM_RAT_PERF_STALLED_CREDITS_VC1 Number of cycles VC1 (request pipeline) is stalled
due to insuf?cient credits.
GM_RAT_PERF_STALLED_TRANSLATION_VC0 Number of cycles VC0 (request pipeline) is stalled
due to unavailable translation data.
GM_RAT_PERF_STALLED_TRANSLATION_VC1 Number of cycles VC1 (request pipeline) is stalled
due to unavailable translation data.
GM_RAT_PERF_TRANSLATION_ERRORS_VC0 Number of translation errors seen on VC0 (request
pipeline).
GM_RAT_PERF_TRANSLATION_ERRORS_VC1 Number of translation errors seen on VC1 (request
pipeline).
GM_RAT_PERF_TRANSLATIONS_VC0 Number of translations requested on VC0 (request
pipeline).
GM_RAT_PERF_TRANSLATIONS_VC1 Number of translations requested on VC1 (request
pipeline).
S–0025–10 19Using the Cray Gemini Hardware Counters
Table 9. RMT Performance Counters
Name Description
GM_RMT_PERF_PUT_BYTES_RX Tally of bytes received in all PUT packets that had
the RMT Enable ?eld set that entered and exited the
RMT with OK status.
GM_RMT_PERF_PUT_CAM_EVIT PUT sequences evicted from the CAM.
GM_RMT_PERF_PUT_CAM_FILL New PUT sequence packet arrived and successfully
allocated in the CAM.
GM_RMT_PERF_PUT_CAM_HITS Packet for PUT sequence currently stored in RMT
arrived and successfully located entry in CAM.
GM_RMT_PERF_PUT_CAM_MISS New PUT sequence packet arrived, but did not
allocate because CAM was full.
GM_RMT_PERF_PUT_PARITY Number of sequences evicted from CAM due to
uncorrectable parity errors.
GM_RMT_PERF_PUT_RECV_COMPLETE Number of MsgRcvComplete packets received
which evicted a CAM entry.
GM_RMT_PERF_PUT_TIMEOUTS Number of sequences evicted from CAM due to
timeout.
GM_RMT_PERF_SEND_BYTES_RX Tally of bytes received in all SEND packets that had
the RMT Enable ?eld set and entered and exited the
RMT with OK status.
GM_RMT_PERF_SEND_CAM_EVIT SEND sequences evicted from the CAM.
GM_RMT_PERF_SEND_CAM_FILL New SEND sequence packet arrived and
successfully allocated in the CAM.
GM_RMT_PERF_SEND_CAM_HITS Packet for SEND sequence currently stored in RMT
arrived and successfully located entry in CAM.
GM_RMT_PERF_SEND_CAM_MISS New SEND sequence packet arrived, but did not
allocate because CAM was full.
GM_RMT_PERF_SEND_PARITY Number of sequences evicted from CAM due to
uncorrectable parity errors.
GM_RMT_PERF_SEND_ABORTS Number of SEND sequences that were aborted.
GM_RMT_PERF_SEND_TIMEOUTS Number of sequences evicted from CAM due to
timeout.
20 S–0025–10Overview of Gemini Hardware Counters
Table 10. SSID Performance Counters
Name Description
GM_SSID_PERF_COMPLETION_COUNT_1 Provides a count of completed request packet
sequences. The type of sequence completions
counted by this register is controlled by the
SSID Performance – Completion Count
Selector Register.
GM_SSID_PERF_COMPLETION_COUNT_2 Provides a count of completed request packet
sequences. The type of sequence completions
counted by this register is controlled by the
SSID Performance – Completion Count
Selector Register.
GM_SSID_PERF_COMPLETION_COUNT_SELECTOR Speci?es the types of completion events
that are counted in the SSID Performance
– Completion Count 1 Register (bits 3-0)
and the SSID Performance – Completion
Count 2 Register (bits 11-8). See the table of
SSID_PerfCompletionCountSelect Encoding
values for encoding of these ?elds.
GM_SSID_PERF_OUT_STALLED_DURATION The accumulated number of cycles of cclk for
which the SSID had a valid ?it available to
send to the ORB but sending of the ?it had
to be stalled while waiting for a credit from
the ORB. This value is cleared by writing any
value to this register.
GM_SSID_PERF_OUTOFSSIDS_COUNT The number of Allocate SSID requests that
have been received for which processing of
the request had to be stalled for one or more
clock cycles because a free SSID was not
immediately available to service the request.
This value is cleared by writing any value to
this register.
GM_SSID_PERF_OUTOFSSIDS_DURATION The accumulated number of cycles of cclk for
which processing of Allocate SSID requests
has been stalled because a free SSID is not
available to service the request. This value is
cleared by writing any value to this register.
S–0025–10 21Using the Cray Gemini Hardware Counters
Name Description
GM_SSID_PERF_SSID_ALLOCATE_COUNT The total number of Allocate SSID requests
that have been received, across all channels
(all FMA descriptors and all BTE VCs),
because this register was last cleared, and that
resulted in a SSID actually being allocated.
Allocate SSID requests that do not result
in a SSID being allocated (i.e. redundant
Allocate requests) are not counted. This value
is cleared by writing any value to this register.
GM_SSID_PERF_SSIDS_IN_USE Bits 7-0 specify the number of SSIDs
currently in use across all Request Channels.
This value is not affected by writes to this
register. This ?eld is initialized to its reset
value by a full reset and by an ht reset.
Bits 23-16 specify the maximum number of
SSIDs that have been in use simultaneously,
across all channels (all FMA descriptors
and all BTE Vcs), since this register was
last initialized. This value is initialized to
CurrentSSIDsInUse by writing any
value to this register. This ?eld is initialized
to its reset value by a full reset.
Table 11. Transmit Arbiter Performance Counters
Name Description
GM_TARB_PERF_BTE_BLOCKED Transmit Arbiter (TARB) Performance BTE
Blocked Count
GM_TARB_PERF_BTE_FLITS TARB Performance BTE Flit Count
GM_TARB_PERF_BTE_PKTS TARB Performance BTE Packet Count
GM_TARB_PERF_BTE_STALLED TARB Performance BTE Stalled Count
GM_TARB_PERF_FMA_BLOCKED TARB Performance FMA Blocked Count
GM_TARB_PERF_FMA_FLITS TARB Performance FMA Flit Count
GM_TARB_PERF_FMA_PKTS TARB Performance FMA Packet Count
GM_TARB_PERF_FMA_STALLED TARB Performance FMA Stalled Count
GM_TARB_PERF_LB_BLOCKED TARB Performance LB Blocked Count
GM_TARB_PERF_LB_FLITS TARB Performance LB Flit Count
GM_TARB_PERF_LB_PKTS TARB Performance LB Packet Count
22 S–0025–10Overview of Gemini Hardware Counters
Name Description
GM_TARB_PERF_LB_STALLED TARB Performance LB Stalled Count
GM_TARB_PERF_OUT_FLITS TARB Performance Output Flit Count
GM_TARB_PERF_OUT_PKTS TARB Performance Output Packet Count
GM_TARB_PERF_OUT_STALLED TARB Performance Output Stalled Count
1.3 Gemini Tile MMRs
The Gemini network consists of 48 tiles, arranged in 6 rows of 8 columns. Within
each tile there are memory-mapped registers associated with the LCB and with the
rest of the tile. The local block has shared connections to each row of tiles.
By default, when only the name of the MMR is used, an event is counted on all 48
tiles. To address an individual tile, append the row (0-5) and column (0-7) to the
name, as shown in the table.
Table 12. Description of Gemini Tile MMRs
Name Description
GM_TILE_PERF_VC0_PHIT_CNT:n:m Number of vc0 phits read from inq buffer
GM_TILE_PERF_VC1_PHIT_CNT:n:m Number of vc1 phits read from inq buffer
GM_TILE_PERF_VC0_PKT_CNT:n:m Number of vc0 packets read from inq buffer
GM_TILE_PERF_VC10_PKT_CNT:n:m Number of vc1 packets read from inq buffer
GM_TILE_PERF_INQ_STALL:n:m Number of clock periods a valid reference is blocked
from the routing pipeline.
GM_TILE_PERF_CREDIT_STALL:n:m Number of clock periods a valid reference is stalled in
the column buffers, waiting on transmissions credits.
S–0025–10 23Using the Cray Gemini Hardware Counters
© 2010 Cray Inc. All Rights Reserved. This document or parts thereof may not be reproduced in any form unless
permitted by contract or by written permission of Cray Inc.
Cray, LibSci, PathScale, and UNICOS are federally registered trademarks and Active Manager, Baker, Cascade,
Cray Apprentice2, Cray Apprentice2 Desktop, Cray C++ Compiling System, Cray CX, Cray CX1, Cray CX1-iWS,
Cray CX1-LC, Cray CX1000, Cray CX1000-C, Cray CX1000-G, Cray CX1000-S, Cray CX1000-SC,
Cray CX1000-SM, Cray CX1000-HN, Cray Fortran Compiler, Cray Linux Environment, Cray SHMEM, Cray X1,
Cray X1E, Cray X2, Cray XD1, Cray XE, Cray XE6, Cray XMT, Cray XR1, Cray XT, Cray XTm, Cray XT3,
Cray XT4, Cray XT5, Cray XT5
h
, Cray XT5m, Cray XT6, Cray XT6m, CrayDoc, CrayPort, CRInform, ECOphlex,
Gemini, Libsci, NodeKARE, RapidArray, SeaStar, SeaStar2, SeaStar2+, Threadstorm, UNICOS/lc, UNICOS/mk,
and UNICOS/mp are trademarks of Cray Inc.
Version 1.0 Published July 2010 Supports CrayPat release 5.1 and CLE release 3.1 running on Cray XT systems.
24 S–0025–10
Using the Cray XMT™ for all streams Pragmas
Abstract
This document describes the for all streams compiler directives and how to
use them to execute a block of code on multiple streams.© 2010 Cray Inc. All Rights Reserved. This document or parts thereof may not be reproduced in any form unless
permitted by contract or by written permission of Cray Inc.
Cray, LibSci, and PathScale are federally registered trademarks and Active Manager, Baker, Cascade, Cray Apprentice2,
Cray Apprentice2 Desktop, Cray C++ Compiling System, Cray CX, Cray CX1, Cray CX1-iWS, Cray CX1-LC,
Cray CX1000, Cray CX1000-C, Cray CX1000-G, Cray CX1000-S, Cray CX1000-SC, Cray CX1000-SM,
Cray CX1000-HN, Cray Fortran Compiler, Cray Linux Environment, Cray SHMEM, Cray X1, Cray X1E, Cray X2,
Cray XD1, Cray XE, Cray XE6, Cray XMT, Cray XR1, Cray XT, Cray XTm, Cray XT3, Cray XT4, Cray XT5,
Cray XT5
h
, Cray XT5m, Cray XT6, Cray XT6m, CrayDoc, CrayPort, CRInform, ECOphlex, Gemini, Libsci,
NodeKARE, RapidArray, SeaStar, SeaStar2, SeaStar2+, Threadstorm, and UNICOS/lc are trademarks of Cray Inc.
UNIX, the “X device,” X Window System, and X/Open are trademarks of The Open Group in the United States and other
countries. All other trademarks are the property of their respective owners.
RECORD OF REVISION
S–0038–14 Published October 2010 Supports 1.4 and later releases running on the Cray XMT hardware.Using the Cray XMT™ for all streams Pragmas
Using the Cray XMT for all streams Pragmas
Overview
In some programming situations it is useful to specify that a block of code should execute exactly once
on each stream of a parallel region, allowing the application to manage data on a per-thread basis.
Effective with the 1.4 release two pragma compiler directives were added that support this.
Description
The syntax of the for all streams pragmas is as follows:
#pragma mta for all streams
This directive starts up a parallel region (if the code is not already in a parallel region)
and cause the next statement or block of statements to be executed exactly once
on every stream allocated to the region. If the pragmas appear in code that would
otherwise not be parallel, they cause it to go parallel. For example,
#pragma mta for all streams
printf("Stream checking in\n");
would cause every stream to print the phrase "Stream checking in" once.
In this example the pragma executes a block of code that increments a counter before
printing the phrase:
int counter = 0;
#pragma mta for all streams
{
counter++;
printf("%d streams checked in \n", counter)
};
#pragma mta for all streams i of n
This directive is similar to the for all streams pragma except that it also sets the
variable n to the total number of streams executing the region, and the variable i to a
unique per-stream identifier between 0 and n-1. For example:
int i, n;
int check_in_array[MAX_PROCESSORS * MAX_STREAMS_PER_PROCESSOR];
for (int i = 0; i < MAX_PROCESSORS * MAX_STREAMS_PER_PROCESSOR; i++)
check_in_array[i] = 0;
#pragma mta for all streams i of n
{
check_in_array[i] = 1;
printf("Stream %d of %d checked in.\n", i, n);
}
Note that the integer variables i and n must be declared separately from the pragma.
S–0038–14 3Using the Cray XMT™ for all streams Pragmas
You can use the for all streams pragmas in conjunction with the use n streams pragma to
ask the compiler to allocate a certain number of streams per processor to the parallel region executing
the for all streams block.
#pragma mta use 100 streams
#pragma mta for all streams
{// do something
}
Be aware, however, that there is no guarantee that the runtime will grant the requested number of
streams. For example, sufficient streams may not be available due to other jobs, the OS, or other
simultaneous parallel regions in the current job.
Examples
In the following example, taken from a breadth-first search procedure, the for all streams
pragma is used to divide a data structure between threads.
int processQueue(int *Q,unsigned &head, unsigned &tail, unsigned qcap,
const Neighbor neighbors[],
const int numNeighbors[], sync int *Marked)
{
#pragma mta trace "process"
#pragma mta noalias *Q, *Marked, *neighbors, *numNeighbors
// elements [head,tail) are readonly
// we can write to other elements of Q
const unsigned oldtail = tail;
const unsigned oldhead = head;
unsigned newhead = head;
unsigned stubbed = 0;
#pragma mta use 100 streams
#pragma mta for all streams
{
unsigned outhead = 0, outtail = 0;
for(;;) {
// grab INBLOCK nodes (& stubs) from the input
unsigned inhead = int_fetch_add(&newhead, INBLOCK);
// avoid overrun
unsigned intail = std::min(inhead + INBLOCK, oldtail);
if (inhead>=intail) break; // stop if we ran out of work
#pragma mta assert nodep *Q,*numNeighbors,*neighbors
for(int i=inhead; i=0) {
int begin = numNeighbors[u]; // |N|
int end = numNeighbors[u+1]; // |N|
#pragma mta assert nodep *Q, *neighbors, *Marked
for(int j=begin;j=outtail) {
outhead = int_fetch_add(&tail, OUTBLOCK);
outtail = outhead+OUTBLOCK;
}
Q[(outhead++)%qcap] = v; // |N|
}else {
Marked[v] = mark; // unlock & keep mark
}
}
}
}
}
#ifdef PHASES
stubbed += outtail-outhead;
#endif
// stub-out the rest of reserved space
// ), where is the number
of streams the compiler requests.Limiting Loop Parallelism in Cray XMT™ Application
S–0027–14 Cray Inc. 7
? Limits the number of processors used by a multiprocessor parallel loop to max(1, c /
), where is the number
of streams the compiler requests for each processor used by the parallel loop.
? If c is larger than or equal to , the total number of
streams used by the parallel loop will be at most c.
? If c is less than , one processor will be used and
streams will be requested by the compiler.
? Limits the number of futures created for a loop that uses loop future parallelism to c.
? If multiple max concurrency c pragmas are specified on one loop, the value of c
specified by the last pragma will be used.
? For collapsible loop nests, the max concurrency value specified by the outer loop (if
any) will be used for the collapsed loop.
? The max concurrency c pragma is not allowed to be used on a loop that also uses the
use n streams pragma.
Examples
The following example illustrates using the max concurrency c pragma on a single processor
parallel loop.
/* Use at most 95 streams. */
#pragma mta loop single processor
#pragma mta max concurrency 95
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}
The following example illustrates using the max concurrency c pragma on a multiprocessor
parallel loop.
/* Use at most 512 streams across all processors. */
#pragma mta max concurrency 512
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}Limiting Loop Parallelism in Cray XMT™ Application
S–0027–14 Cray Inc. 8
The following example illustrates using the max concurrency c pragma on a loop that uses
loop future parallelism.
/* Create at most 512 futures. */
#pragma mta loop future
#pragma mta max concurrency 512
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}
Multiprocessor parallel loops are allowed to use both the max n processors and max
concurrency c pragmas, and can use both on a single loop. In cases where both pragmas are
used, the lower bound of the number of processors estimated by the two limits will be the
limit used on the loop. For example, the following code illustrates the use of both pragmas on
one multiprocessor parallel loop.
/* Use at most 512 streams across all processors or
* at most 8 processors, whichever is smaller.
*/
#pragma mta max concurrency 512
#pragma mta max 8 processors
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}
In the above example, if the compiler were to request 64 streams per processor, then the max
concurrency 512 would estimate that 8 processors should be used for the loop (i.e., 512/64).
The max 8 processors has the same limit on the number of processors so the loop would be
limited to 8 processors. If the compiler instead requested 32 streams per processor, then the
max concurrency 512 would estimate that 16 processors should be used, which is more than
the limit of 8 specified by the max 8 processors, so the loop would be limited to 8 processors.
Because the use n streams pragma cannot be used on the same loop as a max concurrency c
pragma, the loop will use the default number of streams determined by the compiler. The user
will need to look at the canal details for a loop to determine the default number of streams
being requested by the compiler.
Effect of Pragmas on Loop Fusion and Parallel Region Merging
The new pragmas can prevent the compiler from fusing loops if the loops involved do not
have the same limits for the max processors and max concurrency. This is because the
compiler will need to put the loops into different parallel regions in order to limit the
processors and/or concurrency as requested by the user. This could potentially have a negative
impact on the performance of a user's application, so users may need to look at the canal
output to see what loops the compiler fused.Limiting Loop Parallelism in Cray XMT™ Application
S–0027–14 Cray Inc. 9
The pragmas could also prevent the compiler from merging the parallel regions for different
loops into a single parallel region. The limitation for concurrency or processors specified by
the new pragmas applies to the current parallel region that contains the loop with the pragmas.
The compiler must ensure that all loops in a parallel region have the same limits for max
processors and max concurrency. If the loops do not have matching limits, the compiler will
put them in different parallel regions to ensure the user's limits on processors and/or
concurrency can be correctly applied. This could potentially have a negative impact on the
performance of a user's application because more time will be spent tearing down and starting
new parallel regions. In the case of nested parallel regions, any limitations for concurrency or
processors specified with the pragmas on either region do not affect the other region. For
example, if the outer parallel region has a max 8 processors, that pragma will not affect the
inner parallel region because the pragmas apply to the current parallel region only. The user
can determine what loops the compiler placed in a parallel region by looking at the canal
output. The “Additional Loop Details” shows which parallel region a loop is in, and the
details for parallel regions state what limits for processors or concurrency (if any) are being
applied to the region.
The following is an example of two loops that have matching limits for max n processors
that could be fused and placed into one parallel region by the compiler.
#pragma mta max 64 processors
for(i = 0; i < size; i++)
array[i] = i;
#pragma mta max 64 processors
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}
The following is an example of two loops that cannot be fused or put into one parallel region
because the loops specify different limits for the max processors.
#pragma mta max 256 processors
for(i = 0; i < size; i++)
array[i] = i;
#pragma mta max 512 processors
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}
The following is another example of two loops that cannot be fused or put into one parallel
region because the loops specify different limits for the max processors. The first loop does
not use the max n processors pragma, which implies there is no user specified limit.
for(i = 0; i < size; i++)
array[i] = i;Limiting Loop Parallelism in Cray XMT™ Application
S–0027–14 Cray Inc. 10
#pragma mta max 512 processors
for(i = 0; i < size; i++) {
array[i] += array[i] + (size + i);
}
Use Case: Applying Max Processors Pragma to GraphCT
An example application that uses nested parallelism to improve system utilization and reduce
contention on shared data structures is GraphCT (Graph Characterization Toolkit) [1].
GraphCT consists of multiple kernels that perform operations on a graph and the kernel
focused on in this example is betweenness centrality.
The betweenness centrality kernel of GraphCT is executed concurrently by a small number of
threads using loop future parallelism, and each thread uses multiprocessor parallelism to
compute the betweenness centrality of a node. The betweenness centrality kernel of GraphCT
can see significant variance in performance due to issues with load balancing across the
threads. The max n processors pragma can be used to help improve load balancing and
increase utilization by evenly distributing the processors across the threads.
The betweenness centrality kernel of GraphCT consists of two functions, kcentrality and
kcent_core. The kcentrality function creates a small number of threads using loop
future parallelism, and each of those threads calls kcent_core to compute the betweenness
centrality for the nodes in the graph. Both of these functions were updated to make use of the
new max n processors pragma.
The changes to kcent_core are limited to applying the max n processors pragma to each
parallel loop in the function. The limit for the number of processors to use per thread was
determined experimentally based on the default number of threads created in kcentrality
in the release version 0.4 of GraphCT, which is 20. This would give each thread
approximately 6 processors on a 128P XMT system if each thread got the same number of
processors. This led to trying a limit of 8 processors per thread in kcent_core.
Experiments showed that using 8 processors per thread performed better than the release
version of GraphCT with 20 threads and no max n processors pragmas. A power of two was
chosen so the number of processors in the system could be easily divided by the number of
processors used per thread. A limit of 16 processors per thread was also tested and was shown
to have reasonable performance that could be very similar to the performance with a limit of
8, especially for larger graphs (scale >= 28). The following code snippets show how the max
n processors pragma was used for each loop in kcent_core. In these examples,
MAX_PROCS is a preprocessor macro that has been defined as 8.
<...>
#pragma mta max MAX_PROCS processors
#pragma mta assert nodep
for (j = 0; j < NV; j++) {marks[j] = sigma[NV*(K+1) + j] =
0;}
<...>Limiting Loop Parallelism in Cray XMT™ Application
S–0027–14 Cray Inc. 11
#pragma mta max MAX_PROCS processors
#pragma mta assert nodep
for (j = 0; j < (K+1)*NV; j++) {
dist[j] = -1;
sigma[j] = child_count[j] = 0;
}
<...>
#pragma mta max MAX_PROCS processors
#pragma mta assert no dependence
#pragma mta block dynamic schedule
#pragma mta use 100 streams
for (j = Qstart; j < Qend; j++) {
<...>
#pragma mta max MAX_PROCS processors
#pragma mta assert nodep
#pragma mta assert no alias *sigma *Q *child *start *QHead
#pragma mta use 100 streams
for (n = QHead[p]; n < QHead[p+1]; n++) {
<...>
#pragma mta max MAX_PROCS processors
for (j=0; j<(K+1)*NV; j++) delta[j] = 0.0;
<...>
#pragma mta max MAX_PROCS processors
#pragma mta assert nodep
#pragma mta block dynamic schedule
#pragma mta assert no alias *sigma *Q *BC *delta *child *start
*QHead
#pragma mta use 100 streams
for (n = Qstart; n < Qend; n++) {
<...>
The pragma was used on all parallel loops in the function to ensure that each thread that calls
kcent_core is limited to the desired number of processors, which is 8 in this case. Also,
because all of the parallel loops in kcent_core have the same limit for the max processors,
the compiler will not need to put the loops into different parallel regions because of a
mismatch in limits. Grouping the loops into one region can help reduce the cost of going
parallel and improve performance by avoiding starting and tearing down multiple parallel
regions.
The kcentrality function was modified to compute the number of threads at runtime
based on the number of processors used by the application and the number of processors used
per thread in kcent_core. The number of threads, INC, is a preprocessor macro in version
0.4 of GraphCT. However, the modifications to kcentrality changed INC to a variable
that is computed at runtime. The following code snippet shows the changes made to
kcentrality. Again, MAX_PROCS used in the example below has been defined as 8.Limiting Loop Parallelism in Cray XMT™ Application
S–0027–14 Cray Inc. 12
<...>
/*Compute INC based on the number of processors we're using
and limiting each thread to MAX_PROCS processors (in
kcent_core()).*/
int INC;
INC = mta_get_max_teams();
INC = INC / MAX_PROCS;
INC = MTA_INT_MAX(1, INC);
<...>
#pragma mta loop future
for(x=0; x
for (int claimedk = int_fetch_add (&k, 1);
claimedk < Vs;
claimedk = int_fetch_add (&k, 1))
{
<...>
kcent_core(G, BC, K, s, Q, dist, sigma, marks, QHead,
child, child_count);
<...>
}
}
<...>
These changes to GraphCT helped the betweenness centrality kernel have better load
balancing across the threads and achieve higher system utilization, which improved the
performance and scalability of the kernel.
References
[1] “GraphCT – Streaming Graph Analysis”,
http://trac.research.cc.gatech.edu/graphs/wiki/GraphCT, May 4, 2010.
June 2004
version 6.5
TotalView
New FeaturesCopyright © 1999–2004 by Etnus LLC. All rights reserved.
Copyright © 1996–1998 by Dolphin Interconnect Solutions, Inc.
Copyright © 1993–1996 by BBN Systems and Technologies, a division of BBN Corporation.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written permission of Etnus LLC. (Etnus).
Use, duplication, or disclosure by the Government is subject to restrictions as set forth in subparagraph (c)(1)(ii) of the Rights
in Technical Data and Computer Software clause at DFARS 252.227-7013.
Etnus has prepared this manual for the exclusive use of its customers, personnel, and licensees. The information in this manual is subject to change without notice, and should not be construed as a commitment by Etnus. Etnus assumes no responsibility for any errors that appear in this document.
TotalView and Etnus are registered trademarks of Etnus LLC.
TotalView uses a modified version of the Microline widget library. Under the terms of its license, you are entitled to use these
modifications. The source code is available at http://www.etnus.com/Products/TotalView/developers.
All other brand names are the trademarks of their respective holders.TotalView New Features: 6.5 iii
Contents
New Features
New Platforms and Compilers ................................................................................. 1
New and Changed GUI Features ............................................................................. 2
Tools > Memory Debugging Command Added ....................................................... 2
Node Display in the Variable Window ....................................................................... 4
STL String data types Transformed .......................................................................... 4
Type Transformations ............................................................................................... 4Contents
iv 6.5TotalView New Features: version 6.5 1
New Features
This booklet contains information about changes made to TotalView for
version 6.5.
The information in this document is to let you know what changes have
occurred. You’ll find descriptions for all changes within the TotalVie w Us e r s
Guide.
TotalView has many features and it gives you a great number of tools for
finding your program’s problems. An easy way to get acquainted with these
features is to subscribe to the “Tip of the Week”. If you subscribe to this
mailing list, you’ll receive an email message every week that tells you something about TotalView.
¦ All of the tips are archived on our web site at http://www.etnus.com/
Support/Tips/index.html.
¦ If you like what you see, you can subscribe at http://www.etnus.com/
mojo/mojo.cgi.
New Platforms and Compilers
TotalView now supports the following operating system versions:
¦ Red Hat Fedora Core 1 on x86 architectures.
¦ SuSE Linux Profession 9.0 and SuSe Linux Personal on x86 and x86-64
architectures.
TotalView now supports the following compilers:
¦ gcc 3.4.0 for C and C++ on most platforms.
¦ gcc 3.4.0 for Fortran 77 on x86, x86-64, and ia64 Linux.
¦ Intel C and C++ 8.0.066 on x86 and ia64 Linux.
¦ Intel Fortran 8.0.046 on x86 and ia64 Linux
¦ Portland Group C and C++ 5.1 on x86 and x86-64 Linux.
For complete information, see the TotalView Platforms Guide.New Features
2 version 6.5
New and Changed GUI Features
Tools > Memory
Debugging
Command Added
This release of TotalView adds to the memory debugging features that previously existed within TotalView. It also consolidates memory debugging
interactions within one window.
The TotalView Memory Debugger can help you locate many of your
program’s memory problems. For example, you can:
¦ Stop execution when free(), realloc(), and other heap API problems occur.
If your program tries to free memory that it can’t or shouldn’t free, the
Memory Debugger can stop execution. This lets you can identify the
statement that caused the problem.
¦ List leaks.
The Memory Debugger can display your program’s leaks. (Leaks are memory blocks that are allocated, but which are no longer referenced.)
When your program allocates a memory block, the Memory Debugger creates a backtrace. When it makes a list of your leaks, it includes this backtrace in the list. This lets you see the place where your program allocated
the memory block.
¦ Paint allocated and deallocated blocks.
When your program’s memory manager allocates or deallocates memory,
the Memory Debugger can write a bit pattern into it. Writing this bit pattern is called painting.
When you see this bit pattern in a Variable or Expression List Window, you
can tell that you are using memory before your program initializes it or
after your program deallocates it. Depending upon the architecture, you
might even be able to force an exception when your program accesses
this memory.
¦ Identify dangling pointers.
A dangling pointer is a pointer that points into deallocated memory. If the
pointer being displayed in a Variable is dangling, TotalView adds information to the data element so that you know about the problem.
¦ Hold onto deallocated memory.
When trying to identify memory problems, holding on to memory after
your program releases it can sometimes help locate problems. Holding
onto freed memory is called hoarding.
For example, retaining a block can sometimes force a memory error to
occur. Or, when coupled with painting, you’ll be able to tell when your
program is trying to access deallocated memory.New and Changed GUI Features
TotalView New Features 3
After you select the Tools > Memory Debugging command, TotalView displays the following window:New Features
4 version 6.5
If memory debugging is enabled, you can tell the Memory Debugger to display information whenever execution stops. For example, here is a window
showing leak information:
The Backtrace Pane shows the stack frames that existed when your program allocated a memory block. The Source Pane shows the line where it
made the allocation.
For more information, see the Debugging Memory Problems Using TotalView
document.
Node Display in
the Variable
Window
The View > Nodes command was removed. This command was only used
when viewing UPC variables. You can see the nodes upon which a variable
resides by right-clicking on the column headers and selecting Node.
STL String data
types Transformed
STLView now transforms String data types.
Type
Transformations
The way in which you create type transformations has been simplified.
While older methods still work, the new methods are more direct. For information, see the “Creating Type Transformations” chapter of the TotalView Reference Guide.
The Type Transformations Guide has been archived on our web site. It is will no
longer be updated. However, it may be useful if you are attempting to
transform a very difficult data structure or class.
PGI
®
User’s Guide
Parallel Fortran, C and C++ for Scientists and Engineers
The Portland Group™
STMicroelectronics
Two Centerpointe Drive
Lake Oswego, OR 97035While every precaution has been taken in the preparation of this document, The Portland Group™, a wholly-owned subsidiary of STMicroelectronics, makes no warranty
for the use of its products and assumes no responsibility for any errors that may appear, or for damages resulting from the use of the information contained herein. The
Portland Group retains the right to make changes to this information at any time, without notice. The software described in this document is distributed under license from
STMicroelectronics and may be used or copied only in accordance with the terms of the license agreement. No part of this document may be reproduced or transmitted in any
form or by any means, for any purpose other than the purchaser's personal use without the express written permission of The Portland Group.
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this manual, The
Portland Group was aware of a trademark claim. The designations have been printed in caps or initial caps. Thanks is given to the Parallel Tools Consortium and, in particular,
to the High Performance Debugging Forum for their efforts.
PGF95, PGF90, PGC++, Cluster Development Kit, CDK, PGI Unified Binary, PGI Visual Fortran, PVF and The Portland Group are trademarks and PGI, PGHPF, PGF77, PGCC,
PGPROF, and PGDBG are registered trademarks of STMicroelectronics, Inc. Other brands and names are the property of their respective owners. The use of STLport, a C++
Library, is licensed separately and license, distribution and copyright notice can be found in the online documentation for a given release of the PGI compilers and tools.
PGI
®
User’s Guide
Copyright © 1998 – 2000 The Portland Group, Inc.
Copyright © 2000 – 2006 STMicroelectronics, Inc.
All rights reserved.
Printed in the United States of America
First Printing: Release 1.7, Jun 1998
Second Printing: Release 3.0, Jan 1999
Third Printing: Release 3.1, Sep 1999
Fourth Printing: Release 3.2, Sep 2000
Fifth Printing: Release 4.0, May 2002
Sixth Printing: Release 5.0, Jun 2003
Seventh Printing: Release 5.1, Nov 2003
Eight Printing: Release 5.2, Jun 2004
Ninth Printing: Release 6.0, Mar 2005
Tenth Printing: Release 6.1, Dec 2005
Eleventh Printing: Release 6.2, Aug 2006
Twelfth printing: Release 7.0-1, December, 2006
Thirteenth printing: Release 7.1, October, 2007
Technical support: trs@pgroup.com
Sales: sales@pgroup.com
Web: www.pgroup.com/iii
Contents
Preface .................................................................................................................................... xix
Audience Description ............................................................................................................ xix
Compatibility and Conformance to Standards ............................................................................ xix
Organization ......................................................................................................................... xx
Hardware and Software Constraints ........................................................................................ xxii
Conventions ........................................................................................................................ xxii
Related Publications ........................................................................................................... xxvii
1. Getting Started .................................................................................................................... 1
Overview ................................................................................................................................ 1
Invoking the Command-level PGI Compilers ............................................................................... 1
Command-line Syntax ...................................................................................................... 2
Command-line Options .................................................................................................... 3
Fortran Directives and C/C++ Pragmas .............................................................................. 3
Filename Conventions .............................................................................................................. 3
Input Files ..................................................................................................................... 3
Output Files ................................................................................................................... 5
Fortran, C, and C++ Data Types ............................................................................................... 6
Parallel Programming Using the PGI Compilers ........................................................................... 7
Running SMP Parallel Programs ...................................................................................... 7
Running Data Parallel HPF Programs ................................................................................. 8
Platform-specific considerations ................................................................................................ 8
Using the PGI Compilers on Linux .................................................................................... 9
Using the PGI Compilers on Windows .............................................................................. 10
Using the PGI Compilers on SUA and SFU ........................................................................ 11
Using the PGI Compilers on Mac OS X ............................................................................. 11
Site-specific Customization of the Compilers .............................................................................. 12
Using siterc Files ........................................................................................................... 12
Using User rc Files ........................................................................................................ 12
Common Development Tasks .................................................................................................. 13
2. Using Command Line Options ....................................................................................... 15PGI® User’s Guide
iv
Command Line Option Overview ............................................................................................. 15
Command-line Options Syntax ......................................................................................... 15
Command-line Suboptions .............................................................................................. 16
Command-line Conflicting Options ................................................................................... 16
Help with Command-line Options ............................................................................................ 16
Getting Started with Performance ............................................................................................ 18
Using –fast and –fastsse Options ..................................................................................... 18
Other Performance-related Options ................................................................................. 19
Targeting Multiple Systems; Using the -tp Option ....................................................................... 19
Frequently-used Options ......................................................................................................... 19
3. Using Optimization & Parallelization .......................................................................... 21
Overview of Optimization ....................................................................................................... 21
Local Optimization ........................................................................................................ 22
Global Optimization ....................................................................................................... 22
Loop Optimization: Unrolling, Vectorization, and Parallelization ........................................... 22
Interprocedural Analysis (IPA) and Optimization .............................................................. 22
Function Inlining ........................................................................................................... 22
Profile-Feedback Optimization (PFO) .............................................................................. 22
Getting Started with Optimizations ........................................................................................... 23
Local and Global Optimization using -O .................................................................................. 24
Scalar SSE Code Generation ............................................................................................ 26
Loop Unrolling using –Munroll ............................................................................................... 27
Vectorization using –Mvect ..................................................................................................... 28
Vectorization Sub-options ............................................................................................... 28
Vectorization Example Using SSE/SSE2 Instructions ............................................................ 30
Auto-Parallelization using -Mconcur ......................................................................................... 32
Auto-parallelization Sub-options ...................................................................................... 33
Loops That Fail to Parallelize ......................................................................................... 34
Processor-Specific Optimization and the Unified Binary .............................................................. 36
Interprocedural Analysis and Optimization using –Mipa .............................................................. 37
Building a Program Without IPA – Single Step ................................................................... 37
Building a Program Without IPA - Several Steps ................................................................. 38
Building a Program Without IPA Using Make .................................................................... 38
Building a Program with IPA .......................................................................................... 38
Building a Program with IPA - Single Step ........................................................................ 39
Building a Program with IPA - Several Steps ..................................................................... 39
Building a Program with IPA Using Make ........................................................................ 40
Questions about IPA ...................................................................................................... 40
Profile-Feedback Optimization using –Mpfi/–Mpfo ..................................................................... 41
Default Optimization Levels ..................................................................................................... 42
Local Optimization Using Directives and Pragmas ...................................................................... 42
Execution Timing and Instruction Counting ............................................................................... 43
Portability of Multi-Threaded Programs on Linux ....................................................................... 43
libpgbind ..................................................................................................................... 44
libnuma ....................................................................................................................... 44PGI
®
User’s Guide
v
4. Using Function Inlining .................................................................................................. 45
Invoking Function Inlining ..................................................................................................... 45
Using an Inline Library .................................................................................................. 46
Creating an Inline Library ...................................................................................................... 47
Working with Inline Libraries ......................................................................................... 48
Updating Inline Libraries - Makefiles ............................................................................... 48
Error Detection during Inlining ............................................................................................... 49
Examples ............................................................................................................................. 49
Restrictions on Inlining .......................................................................................................... 49
5. Using OpenMP .................................................................................................................. 51
Fortran Parallelization Directives ............................................................................................. 51
C/C++ Parallelization Pragmas ............................................................................................... 52
Directive and Pragma Recognition ........................................................................................... 53
Directive and Pragma Summary Table ...................................................................................... 53
Directive and Pragma Clauses ................................................................................................. 54
Run-time Library Routines ...................................................................................................... 55
Environment Variables ........................................................................................................... 59
OMP_DYNAMIC ............................................................................................................ 59
OMP_NESTED ............................................................................................................... 59
OMP_NUM_THREADS ................................................................................................... 59
OMP_SCHEDULE ........................................................................................................... 60
OMP_STACK_SIZE ......................................................................................................... 60
OMP_WAIT_POLICY ...................................................................................................... 60
6. Using Directives and Pragmas ....................................................................................... 63
PGI Proprietary Fortran Directives ........................................................................................... 63
PGI Proprietary C and C++ Pragmas ....................................................................................... 64
PGI Proprietary Optimization Fortran Directive and C/C++ Pragma Summary ................................. 64
Scope of Fortran Directives and Command-Line options ............................................................. 66
Scope of C/C++ Pragmas and Command-Line Options ............................................................... 67
Prefetch Directives ............................................................................................................... 69
Format Requirements .................................................................................................... 70
Sample Usage ............................................................................................................... 70
!DEC$ Directive .................................................................................................................... 70
Format Requirements .................................................................................................... 71
ALIAS Directive ............................................................................................................. 71
ATTRIBUTES Directive ................................................................................................... 71
DISTRIBUTE Directive .................................................................................................... 72
ALIAS Directive ............................................................................................................. 72
C$PRAGMA C ........................................................................................................................ 72
7. Creating and Using Libraries ........................................................................................ 75
Using builtin Math Functions in C/C++ .................................................................................... 75
Creating and Using Shared Object Files on Linux ....................................................................... 76PGI® User’s Guide
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Creating and Using Shared Object Files in SFU and 32-bit SUA ..................................................... 77
Shared Object Error Message ......................................................................................... 78
Shared Object-Related Compiler Switches ......................................................................... 78
PGI Runtime Libraries on Windows ......................................................................................... 79
Creating and Using Static Libraries on Windows ........................................................................ 79
ar command ................................................................................................................ 79
ranlib command ........................................................................................................... 80
Creating and Using Dynamic-Link Libraries on Windows ............................................................. 80
Using LIB3F ........................................................................................................................ 88
LAPACK, BLAS and FFTs ......................................................................................................... 88
The C++ Standard Template Library ........................................................................................ 88
8. Using Environment Variables ........................................................................................ 89
Setting Environment Variables ................................................................................................. 89
Setting Environment Variables on Linux ............................................................................ 89
Setting Environment Variables on Windows ....................................................................... 90
Setting Environment Variables on Mac OSX ....................................................................... 90
PGI-Related Environment Variables .......................................................................................... 91
PGI Environment Variables ..................................................................................................... 92
FLEXLM_BATCH ............................................................................................................ 93
FORTRAN_OPT ............................................................................................................. 93
GMON_OUT_PREFIX ...................................................................................................... 93
LD_LIBRARY_PATH ....................................................................................................... 93
LM_LICENSE_FILE ......................................................................................................... 93
MANPATH .................................................................................................................... 94
MPSTKZ ....................................................................................................................... 94
MP_BIND ..................................................................................................................... 94
MP_BLIST .................................................................................................................... 95
MP_SPIN ..................................................................................................................... 95
MP_WARN ................................................................................................................... 95
NCPUS ......................................................................................................................... 96
NCPUS_MAX ................................................................................................................. 96
NO_STOP_MESSAGE ...................................................................................................... 96
PATH ........................................................................................................................... 96
PGI ............................................................................................................................. 96
PGI_CONTINUE ............................................................................................................. 97
PGI_OBJSUFFIX ............................................................................................................. 97
PGI_STACK_USAGE ........................................................................................................ 97
PGI_TERM ................................................................................................................... 97
PGI_TERM_DEBUG ....................................................................................................... 99
PWD ............................................................................................................................ 99
STATIC_RANDOM_SEED ................................................................................................. 99
TMP .......................................................................................................................... 100
TMPDIR ..................................................................................................................... 100
Using Environment Modules ................................................................................................. 100
Stack Traceback and JIT Debugging ....................................................................................... 101PGI
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9. Distributing Files - Deployment .................................................................................. 103
Deploying Applications on Linux ............................................................................................ 103
Runtime Library Considerations ..................................................................................... 103
64-bit Linux Considerations .......................................................................................... 104
Linux Redistributable Files ............................................................................................ 104
Restrictions on Linux Portability .................................................................................... 104
Installing the Linux Portability Package ........................................................................... 104
Licensing for Redistributable Files ................................................................................. 105
Deploying Applications on Windows ....................................................................................... 105
PGI Redistributables .................................................................................................... 105
Microsoft Redistributables ............................................................................................ 105
Code Generation and Processor Architecture ........................................................................... 106
Generating Generic x86 Code ........................................................................................ 106
Generating Code for a Specific Processor ........................................................................ 106
Generating Code for Multiple Types of Processors in One Executable .......................................... 106
Unified Binary Command-line Switches ........................................................................... 107
Unified Binary Directives and Pragma ............................................................................. 107
10. Inter-language Calling ................................................................................................ 109
Overview of Calling Conventions ............................................................................................ 109
Inter-language Calling Considerations ..................................................................................... 110
Functions and Subroutines ................................................................................................... 110
Upper and Lower Case Conventions, Underscores .................................................................... 111
Compatible Data Types ......................................................................................................... 111
Fortran Named Common Blocks .................................................................................... 112
Argument Passing and Return Values ..................................................................................... 113
Passing by Value (%VAL) ............................................................................................. 113
Character Return Values ............................................................................................... 113
Complex Return Values ................................................................................................ 114
Array Indices ...................................................................................................................... 114
Examples ........................................................................................................................... 115
Example - Fortran Calling C .......................................................................................... 115
Example - C Calling Fortran .......................................................................................... 115
Example - C ++ Calling C ............................................................................................ 116
Example - C Calling C++ ............................................................................................. 117
Example - Fortran Calling C++ ..................................................................................... 118
Example - C++ Calling Fortran ..................................................................................... 119
Win32 Calling Conventions ................................................................................................... 120
Win32 Fortran Calling Conventions ................................................................................ 120
Symbol Name Construction and Calling Example .............................................................. 121
Using the Default Calling Convention .............................................................................. 122
Using the STDCALL Calling Convention ............................................................................ 122
Using the C Calling Convention ...................................................................................... 122
Using the UNIX Calling Convention ................................................................................. 123
11. Programming Considerations for 64-Bit Environments ....................................... 125PGI® User’s Guide
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Data Types in the 64-Bit Environment .................................................................................... 125
C/C++ Data Types ....................................................................................................... 126
Fortran Data Types ...................................................................................................... 126
Large Static Data in Linux ..................................................................................................... 126
Large Dynamically Allocated Data .......................................................................................... 126
64-Bit Array Indexing .......................................................................................................... 126
Compiler Options for 64-bit Programming .............................................................................. 127
Practical Limitations of Large Array Programming .................................................................... 128
Example: Medium Memory Model and Large Array in C ............................................................ 129
Example: Medium Memory Model and Large Array in Fortran .................................................... 130
Example: Large Array and Small Memory Model in Fortran ....................................................... 131
12. C/C++ Inline Assembly and Intrinsics ..................................................................... 133
Inline Assembly ................................................................................................................... 133
Extended Inline Assembly ..................................................................................................... 134
Output Operands ......................................................................................................... 135
Input Operands ........................................................................................................... 137
Clobber List ................................................................................................................ 138
Additional Constraints .................................................................................................. 139
Operand Aliases .......................................................................................................... 145
Assembly String Modifiers ............................................................................................. 145
Extended Asm Macros .................................................................................................. 147
Intrinsics ............................................................................................................................ 148
13. Fortran, C and C++ Data Types ................................................................................ 151
Fortran Data Types .............................................................................................................. 151
Fortran Scalars ........................................................................................................... 151
FORTRAN 77 Aggregate Data Type Extensions .................................................................. 153
Fortran 90 Aggregate Data Types (Derived Types) ............................................................ 154
C and C++ Data Types ....................................................................................................... 154
C and C++ Scalars ...................................................................................................... 154
C and C++ Aggregate Data Types .................................................................................. 156
Class and Object Data Layout ........................................................................................ 156
Aggregate Alignment .................................................................................................... 157
Bit-field Alignment ....................................................................................................... 158
Other Type Keywords in C and C++ .............................................................................. 158
14. C++ Name Mangling ................................................................................................... 159
Types of Mangling ............................................................................................................... 160
Mangling Summary .............................................................................................................. 160
Type Name Mangling ................................................................................................... 160
Nested Class Name Mangling ......................................................................................... 161
Local Class Name Mangling ........................................................................................... 161
Template Class Name Mangling ..................................................................................... 161
15. Command-Line Options Reference ........................................................................... 163PGI
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PGI Compiler Option Summary ............................................................................................. 163
Build-Related PGI Options ............................................................................................ 163
PGI Debug-Related Compiler Options ............................................................................. 166
PGI Optimization-Related Compiler Options .................................................................... 167
PGI Linking and Runtime-Related Compiler Options ......................................................... 167
C and C++ Compiler Options ............................................................................................... 168
Generic PGI Compiler Options .............................................................................................. 170
C and C++ -specific Compiler Options ................................................................................... 208
–M Options by Category ....................................................................................................... 219
–M Code Generation Controls .......................................................................... 220
–M C/C++ Language Controls .......................................................................... 223
–M Environment Controls ................................................................................ 225
–M Fortran Language Controls ......................................................................... 226
–M Inlining Controls ....................................................................................... 228
–M Optimization Controls ................................................................................ 229
–M Miscellaneous Controls .............................................................................. 238
16. OpenMP Reference Information ............................................................................... 243
Parallelization Directives and Pragmas ................................................................................... 243
ATOMIC ............................................................................................................................ 244
BARRIER ............................................................................................................................ 244
CRITICAL ... END CRITICAL and omp critical .......................................................................... 245
C$DOACROSS .................................................................................................................... 246
DO ... END DO and omp for ................................................................................................ 247
FLUSH and omp flush pragma .............................................................................................. 249
MASTER ... END MASTER and omp master pragma ................................................................. 250
ORDERED ......................................................................................................................... 251
PARALLEL ... END PARALLEL and omp parallel ....................................................................... 251
PARALLEL DO .................................................................................................................... 254
PARALLEL SECTIONS ........................................................................................................... 255
PARALLEL WORKSHARE ....................................................................................................... 256
SECTIONS … END SECTIONS .............................................................................................. 257
SINGLE ... END SINGLE ........................................................................................................ 257
THREADPRIVATE ................................................................................................................ 258
WORKSHARE ... END WORKSHARE ......................................................................................... 259
Directive and Pragma Clauses ............................................................................................... 260
Schedule Clause .......................................................................................................... 261
17. Directives and Pragmas Reference ........................................................................... 263
PGI Proprietary Fortran Directive and C/C++ Pragma Summary ................................................. 263
altcode (noaltcode) ............................................................................................................ 263
assoc (noassoc) .................................................................................................................. 264
bounds (nobounds) ........................................................................................................... 265
cncall (nocncall) ................................................................................................................ 265
concur (noconcur) ............................................................................................................ 265
depchk (nodepchk) ............................................................................................................ 265PGI® User’s Guide
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eqvchk (noeqvchk) ............................................................................................................ 265
fcon (nofcon) ..................................................................................................................... 265
invarif (noinvarif) ............................................................................................................... 265
ivdep ................................................................................................................................. 266
lstval (nolstval) ................................................................................................................... 266
opt .................................................................................................................................... 266
safe (nosafe) ...................................................................................................................... 266
safe_lastval ......................................................................................................................... 266
safeptr (nosafeptr) .............................................................................................................. 267
single (nosingle) ................................................................................................................. 268
tp ...................................................................................................................................... 268
unroll (nounroll) ................................................................................................................ 268
vector (novector) ................................................................................................................ 269
vintr (novintr) .................................................................................................................... 269
18. Run-time Environment ................................................................................................ 271
Linux86 and Win32 Programming Model ................................................................................ 271
Function Calling Sequence ............................................................................................ 271
Function Return Values ................................................................................................ 273
Argument Passing ........................................................................................................ 275
Linux86-64 Programming Model ........................................................................................... 277
Function Calling Sequence ............................................................................................ 278
Function Return Values ................................................................................................ 280
Argument Passing ........................................................................................................ 281
Linux86-64 Fortran Supplement .................................................................................... 283
Win64 Programming Model .................................................................................................. 287
Function Calling Sequence ............................................................................................ 288
Function Return Values ................................................................................................ 290
Argument Passing ........................................................................................................ 291
Win64/SUA64 Fortran Supplement ................................................................................. 293
19. C++ Dialect Supported ............................................................................................... 299
Extensions Accepted in Normal C++ Mode ............................................................................. 299
cfront 2.1 Compatibility Mode ............................................................................................... 300
cfront 2.1/3.0 Compatibility Mode ......................................................................................... 301
20. C/C++ MMX/SSE Inline Intrinsics ............................................................................. 303
Using Intrinsic functions ....................................................................................................... 303
Required Header File ................................................................................................... 304
Intrinsic Data Types ..................................................................................................... 304
Intrinsic Example ........................................................................................................ 304
MMX Intrinsics ................................................................................................................... 305
SSE Intrinsics ...................................................................................................................... 306
ABM Intrinsics .................................................................................................................... 309
21. Fortran Module/Library Interfaces ........................................................................... 311PGI
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Data Types ......................................................................................................................... 311
Using DFLIB and DFPORT .................................................................................................... 312
DFLIB ........................................................................................................................ 312
DFPORT ..................................................................................................................... 312
Using the DFWIN module ..................................................................................................... 312
Supported Libraries and Modules .......................................................................................... 313
advapi32 .................................................................................................................... 313
comdlg32 ................................................................................................................... 315
dfwbase ..................................................................................................................... 315
dfwinty ....................................................................................................................... 315
gdi32 ......................................................................................................................... 316
kernel32 .................................................................................................................... 319
shell32 ....................................................................................................................... 327
user32 ....................................................................................................................... 327
winver ....................................................................................................................... 331
wsock32 .................................................................................................................... 332
22. Messages ........................................................................................................................ 333
Diagnostic Messages ............................................................................................................ 333
Phase Invocation Messages ................................................................................................... 334
Fortran Compiler Error Messages .......................................................................................... 334
Message Format .......................................................................................................... 334
Message List ............................................................................................................... 334
Fortran Runtime Error Messages ........................................................................................... 360
Message Format .......................................................................................................... 360
Message List ............................................................................................................... 360
Index ...................................................................................................................................... 363xiixiii
Figures
13.1. Internal Padding in a Structure ............................................................................................. 157
13.2. Tail Padding in a Structure ................................................................................................... 158xivxv
Tables
1. PGI Compilers and Commands .................................................................................................. xxvi
2. Processor Options ................................................................................................................... xxvi
1.1. Stop-after Options, Inputs and Outputs ........................................................................................ 5
1.2. Examples of Using siterc and User rc Files ................................................................................. 13
2.1. Commonly Used Command Line Options .................................................................................... 20
3.1. Optimization and –O, –g and –M Options ........................................................................ 42
5.1. Directive and Pragma Summary Table ....................................................................................... 53
5.2. Run-time Library Call Summary ................................................................................................ 55
5.3. OpenMP-related Environment Variable Summary Table ................................................................ 59
6.1. Proprietary Optimization-Related Fortran Directive and C/C++ Pragma Summary ............................. 65
8.1. PGI-related Environment Variable Summary Table ....................................................................... 91
8.2. Supported PGI_TERM Values ................................................................................................... 98
10.1. Fortran and C/C++ Data Type Compatibility ............................................................................ 111
10.2. Fortran and C/C++ Representation of the COMPLEX Type ......................................................... 112
10.3. Calling Conventions Supported by the PGI Fortran Compilers ..................................................... 120
11.1. 64-bit Compiler Options ....................................................................................................... 127
11.2. Effects of Options on Memory and Array Sizes ......................................................................... 127
11.3. 64-Bit Limitations ................................................................................................................ 128
12.1. Simple Constraints ............................................................................................................... 139
12.2. x86/x86_64 Machine Constraints .......................................................................................... 141
12.3. Multiple Alternative Constraints ............................................................................................. 143
12.4. Constraint Modifier Characters .............................................................................................. 144
12.5. Assembly String Modifier Characters ...................................................................................... 145
12.6. Intrinsic Header File Organization ......................................................................................... 148
13.1. Representation of Fortran Data Types ..................................................................................... 151
13.2. Real Data Type Ranges ........................................................................................................ 152
13.3. Scalar Type Alignment ......................................................................................................... 152
13.4. C/C++ Scalar Data Types ..................................................................................................... 154
13.5. Scalar Alignment ................................................................................................................. 155
15.1. PGI Build-Related Compiler Options ...................................................................................... 164
15.2. PGI Debug-Related Compiler Options ..................................................................................... 166
15.3. Optimization-Related PGI Compiler Options ............................................................................ 167
15.4. Linking and Runtime-Related PGI Compiler Options ................................................................. 167PGI® User’s Guide
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15.5. C and C++ -specific Compiler Options ................................................................................... 168
15.6. Subgroups for –help Option ................................................................................................. 179
15.7. –M Options Summary .......................................................................................................... 185
15.8. Optimization and –O, –g, –Mvect, and –Mconcur Options ........................................................ 193
16.1. Initialization of REDUCTION Variables .................................................................................... 253
16.2. Directive and Pragma Clauses .............................................................................................. 260
18.1. Register Allocation .............................................................................................................. 271
18.2. Standard Stack Frame .......................................................................................................... 272
18.3. Stack Contents for Functions Returning struct/union ................................................................. 274
18.4. Integral and Pointer Arguments ............................................................................................. 275
18.5. Floating-point Arguments ...................................................................................................... 275
18.6. Structure and Union Arguments ............................................................................................ 276
18.7. Register Allocation .............................................................................................................. 278
18.8. Standard Stack Frame .......................................................................................................... 278
18.9. Register Allocation for Example A-2 ....................................................................................... 282
18.10. Linux86-64 Fortran Fundamental Types ................................................................................ 284
18.11. Fortran and C/C++ Data Type Compatibility .......................................................................... 285
18.12. Fortran and C/C++ Representation of the COMPLEX Type ....................................................... 286
18.13. Register Allocation ............................................................................................................. 288
18.14. Standard Stack Frame ........................................................................................................ 288
18.15. Register Allocation for Example A-4 ..................................................................................... 292
18.16. Win64 Fortran Fundamental Types ....................................................................................... 293
18.17. Fortran and C/C++ Data Type Compatibility .......................................................................... 295
18.18. Fortran and C/C++ Representation of the COMPLEX Type ....................................................... 296
20.1. MMX Intrinsics (mmintrin.h) ................................................................................................ 305
20.2. SSE Intrinsics (xmmintrin.h) ................................................................................................ 306
20.3. SSE2 Intrinsics (emmintrin.h) ............................................................................................. 307
20.4. SSE3 Intrinsics (pmmintrin.h) .............................................................................................. 309
20.5. SSSE3 Intrinsics (tmmintrin.h) .............................................................................................. 309
20.6. SSE4a Intrinsics (ammintrin.h) ............................................................................................. 309
20.7. SSE4a Intrinsics (intrin.h) .................................................................................................... 310
21.1. Fortran Data Type Mappings ................................................................................................. 311xvii
Examples
1.1. Hello program ......................................................................................................................... 2
2.1. Makefiles with Options ............................................................................................................ 16
3.1. Dot Product Code ................................................................................................................... 27
3.2. Unrolled Dot Product Code ...................................................................................................... 27
3.3. Vector operation using SSE instructions ..................................................................................... 31
3.4. Using SYSTEM_CLOCK code fragment ........................................................................................ 43
4.1. Sample Makefile ..................................................................................................................... 48
6.1. Prefetch Directive Use ............................................................................................................. 70
7.1. Build a DLL: Fortran ............................................................................................................... 82
7.2. Build a DLL: C ....................................................................................................................... 83
7.3. Build DLLs Containing Circular Mutual Imports: C ....................................................................... 84
7.4. Build DLLs Containing Circular Mutual Imports: Fortran ............................................................... 86
7.5. Import a Fortran module from a DLL ........................................................................................ 87
10.1. Character Return Parameters ................................................................................................ 114
10.2. COMPLEX Return Values ...................................................................................................... 114
10.3. Fortran Main Program fmain.f .............................................................................................. 115
10.4. C function cfunc_ ............................................................................................................... 115
10.5. Fortran Subroutine forts.f ..................................................................................................... 116
10.6. C Main Program cmain.c ..................................................................................................... 116
10.7. Simple C Function cfunc.c .................................................................................................... 116
10.8. C++ Main Program cpmain.C Calling a C Function .................................................................. 117
10.9. Simple C++ Function cpfunc.C with Extern C .......................................................................... 117
10.10. C Main Program cmain.c Calling a C++ Function .................................................................. 117
10.11. Fortran Main Program fmain.f calling a C++ function ............................................................ 118
10.12. C++ function cpfunc.C ...................................................................................................... 118
10.13. Fortran Subroutine forts.f ................................................................................................... 119
10.14. C++ main program cpmain.C ............................................................................................. 119
18.1. C Program Calling an Assembly-language Routine .................................................................... 277
18.2. Parameter Passing ............................................................................................................... 282
18.3. C Program Calling an Assembly-language Routine .................................................................... 283
18.4. Parameter Passing ............................................................................................................... 291
18.5. C Program Calling an Assembly-language Routine .................................................................... 293xviiixix
Preface
This guide is part of a set of manuals that describe how to use The Portland Group (PGI) Fortran, C, and
C++ compilers and program development tools. These compilers and tools include the PGF77, PGF95,
PGHPF, PGC++, and PGCC ANSI C compilers, the PGPROF profiler, and the PGDBG debugger. They work in
conjunction with an x86 or x64 assembler and linker. You can use the PGI compilers and tools to compile,
debug, optimize, and profile serial and parallel applications for x86 (Intel Pentium II/III/4/M, Intel Centrino,
Intel Xeon, AMD Athlon XP/MP) or x64 (AMD Athlon64/Opteron/Turion, Intel EM64T, Intel Core Duo, Intel
Core 2 Duo) processor-based systems.
The PGI User's Guide provides operating instructions for the PGI command-level development environment. It
also contains details concerning the PGI compilers' interpretation of the Fortran language, implementation of
Fortran language extensions, and command-level compilation. Users are expected to have previous experience
with or knowledge of the Fortran programming language.
Audience Description
This manual is intended for scientists and engineers using the PGI compilers. To use these compilers, you
should be aware of the role of high-level languages, such as Fortran, C, and C++, as well as assembly-language
in the software development process; and you should have some level of understanding of programming. The
PGI compilers are available on a variety of x86 or x64 hardware platforms and operating systems. You need to
be familiar with the basic commands available on your system.
Compatibility and Conformance to Standards
Your system needs to be running a properly installed and configured version of the compilers. For information
on installing PGI compilers and tools, refer to the Release and Installation notes included with your software.
For further information, refer to the following:
• American National Standard Programming Language FORTRAN, ANSI X3. -1978 (1978).
• ISO/IEC 1539-1 : 1991, Information technology – Programming Languages – Fortran, Geneva, 1991
(Fortran 90).
• ISO/IEC 1539-1 : 1997, Information technology – Programming Languages – Fortran, Geneva, 1997
(Fortran 95).PGI® User’s Guide
xx
• Fortran 95 Handbook Complete ISO/ANSI Reference, Adams et al, The MIT Press, Cambridge, Mass, 1997.
• High Performance Fortran Language Specification, Revision 1.0, Rice University, Houston, Texas (1993),
http://www.crpc.rice.edu/HPFF.
• High Performance Fortran Language Specification, Revision 2.0, Rice University, Houston, Texas (1997),
http://www.crpc.rice.edu/HPFF.
• OpenMP Application Program Interface, Version 2.5, May 2005, http://www.openmp.org.
• Programming in VAX Fortran, Version 4.0, Digital Equipment Corporation (September, 1984).
• IBM VS Fortran, IBM Corporation, Rev. GC26-4119.
• Military Standard, Fortran, DOD Supplement to American National Standard Programming Language
Fortran, ANSI x.3-1978, MIL-STD-1753 (November 9, 1978).
• American National Standard Programming Language C, ANSI X3.159-1989.
• ISO/IEC 9899:1999, Information technology – Programming Languages – C, Geneva, 1999 (C99).
Organization
Users typically begin by wanting to know how to use a product and often then find that they need more
information and facts about specific areas of the product. Knowing how as well as why you might use certain
options or perform certain tasks is key to using the PGI compilers and tools effectively and efficiently.
However, once you have this knowledge and understanding, you very likely might find yourself wanting to
know much more about specific areas or specific topics. Consequently, his manual is divided into the following
two parts:
• Part I, Compiler Usage, contains the essential information on how to use the compiler.
• Part II, Reference Information, contains more detailed reference information about specific aspects of the
compiler, such as the details of compiler options, directives, and more.
Part I, Compiler Usage, contains these chapters:
Chapter 1, “Getting Started” provides an introduction to the PGI compilers and describes their use and
overall features.
Chapter 2, “Using Command Line Options” provides an overview of the command-line options as well as
task-related lists of options.
Chapter 3, “Using Optimization & Parallelization” describes standard optimization techniques that, with
little effort, allow users to significantly improve the performance of programs.
Chapter 4, “Using Function Inlining” describes how to use function inlining and shows how to create an
inline library.
Chapter 5, “Using OpenMP” provides a description of the OpenMP Fortran parallelization directives and of the
OpenMP C and C++ parallelization pragmas and shows examples of their use.
Chapter 6, “Using Directives and Pragmas” provides a description of each Fortran optimization directive and
C/C++ optimization pragma, and shows examples of their use.Preface
xxi
Chapter 7, “Creating and Using Libraries” discusses PGI support libraries, shared object files, and
environment variables that affect the behavior of the PGI compilers.
Chapter 8, “ Using Environment Variables” describes the environment variables that affect the behavior of the
PGI compilers.
Chapter 9, “Distributing Files - Deployment” describes the deployment of your files once you have built,
debugged and compiled them successfully.
Chapter 10, “Inter-language Calling” provides examples showing how to place C Language calls in a Fortran
program and Fortran Language calls in a C program.
Chapter 11, “Programming Considerations for 64-Bit Environments” discusses issues of which
programmers should be aware when targeting 64-bit processors.
Chapter 12, “C/C++ Inline Assembly and Intrinsics” describes how to use inline assembly code in C
and C++ programs, as well as how to use intrinsic functions that map directly to x86 and x64 machine
instructions.
Part II, Reference Information, contains these chapters:
Chapter 13, “Fortran, C and C++ Data Types” describes the data types that are supported by the PGI Fortran,
C, and C++ compilers.
Chapter 14, “C++ Name Mangling” describes the name mangling facility and explains the transformations of
names of entities to names that include information on aspects of the entity’s type and a fully qualified name.
Chapter 15, “Command-Line Options Reference” provides a detailed description of each command-line
option.
Chapter 16, “OpenMP Reference Information”contains detailed descriptions of each of the OpenMP
directives and pragmas that PGI supports.
Chapter 17, “Directives and Pragmas Reference”contains detailed descriptions of PGI’s proprietary directives
and pragmas.
Chapter 18, “Run-time Environment” describes the assembly language calling conventions and examples of
assembly language calls.
Chapter 19, “C++ Dialect Supported” lists more details of the version of the C++ language that PGC++
supports.
Chapter 20, “C/C++ MMX/SSE Inline Intrinsics,” on page 303 provides tables that list the MMX Inline
Intrinsics (mmintrin.h), the SSE1 inline intrinsics (xmmintrin.h), and SSE2 inline intrinsics (emmintrin.h).
Chapter 21, “Fortran Module/Library Interfaces” provides a description of the Fortran module library
interfaces that PVF supports, describing each property available.
Chapter 22, “Messages” provides a list of compiler error messages.PGI® User’s Guide
xxii
Hardware and Software Constraints
This guide describes versions of the PGI compilers that produce assembly code for x86 and x64 processorbased systems. Details concerning environment-specific values and defaults and system-specific features or
limitations are presented in the release notes delivered with the PGI compilers.
Conventions
The PGI User's Guide uses the following conventions:
italic
Italic font is for commands, filenames, directories, arguments, options and for emphasis.
Constant Width
Constant width font is for examples and for language statements in the text, including assembly language
statements.
[ item1 ]
Square brackets indicate optional items. In this case item1 is optional.
{ item2 | item 3}
Braces indicate that a selection is required. In this case, you must select either item2 or item3.
filename...
Ellipsis indicate a repetition. Zero or more of the preceding item may occur. In this example, multiple
filenames are allowed.
FORTRAN
Fortran language statements are shown in the text of this guide using upper-case characters and a reduced
point size.
The PGI compilers and tools are supported on both 32-bit and 64-bit variants of Linux, Windows, and Mac
OS operating systems on a variety of x86-compatible processors. There are a wide variety of releases and
distributions of each of these types of operating systems. The PGI User’s Guide defines the following terms with
respect to these platforms:
AMD64
a 64-bit processor from AMD, designed to be binary compatible with IA32 processors, and incorporating
new features such as additional registers and 64-bit addressing support for improved performance and
greatly increased memory range.
Barcelona
the Quad-Core AMD Opteron(TM) Processor, that is, Opteron Rev x10
DLL
a dynamic linked library on Win32 or Win64 platforms of the form xxx.dll containing objects that are
dynamically linked into a program at the time of execution.
driver
the compiler driver controls the compiler, linker, and assembler, and adds objects and libraries to create
an executable. The -dryrun option illustrates operation of the driver. pgf77, pgf95, pghpf, pgcc, pgCCPreface
xxiii
(Linux), and pgcpp are drivers for the PGI compilers. A pgf90 driver is retained for compatibility with
existing makefiles, even though pgf90 and pgf95 drivers are identical.
Dual-core
Dual-, Quad-, or Multi-core - some x64 CPUs incorporate two or four complete processor cores
(functional units, registers, level 1 cache, level 2 cache, etc) on a single silicon die. These are referred to
as Dual-core or Quad-core (in general, Multi-core) processors. For purposes of OpenMP or auto-parallel
threads, or MPI process parallelism, these cores function as distinct processors. However, the processing
cores are on a single chip occupying a single socket on the system motherboard. In PGI 7.1, there are no
longer software licensing limits on OpenMP threads for Multi-core.
EM64T
a 64-bit IA32 processor with Extended Memory 64-bit Technology extensions that are binary compatible
with AMD64 processors. This includes Intel Pentium 4, Intel Xeon, and Intel Core 2 processors.
hyperthreading (HT)
some IA32 CPUs incorporate extra registers that allow 2 threads to run on a single CPU with improved
performance for some tasks. This is called hyperthreading and abbreviated HT. Some linux86 and
linux86-64 environments treat IA32 CPUs with HT as though there were a 2nd pseudo CPU, even though
there is only one physical CPU. Unless the Linux kernel is hyperthread-aware, the second thread of an
OpenMP program will be assigned to the pseudo CPU, rather than a real second physical processor (if one
exists in the system). OpenMP Programs can run very slowly if the second thread is not properly assigned.
IA32
an Intel Architecture 32-bit processor, designed to be binary compatible with x86 processors, and
incorporating new features such as streaming SIMD extensions (SSE) for improved performance.
Large Arrays
arrays with aggregate size larger than 2GB, which require 64-bit index arithmetic for accesses to elements
of arrays. If -Mlarge_arrays is specified and -mcmodel=medium is not specified, the default small memory
model is used, and all index arithmetic is performed in 64-bits. This can be a useful mode of execution
for certain existing 64-bit applications that use the small memory model but allocate and manage a single
contiguous data space larger than 2GB.
linux86
32-bit Linux operating system running on an x86 or x64 processor-based system, with 32-bit GNU tools,
utilities and libraries used by the PGI compilers to assemble and link for 32-bit execution.
linux86-64
64-bit Linux operating system running on an x64 processor-based system, with 64-bit and 32-bit GNU
tools, utilities and libraries used by the PGI compilers to assemble and link for execution in either linux86
or linux86-64 environments. The 32-bit development tools and execution environment under linux86-64
are considered a cross development environment for x86 processor-based applications.
Mac OS X
collectively, all osx86 and osx86-64 platforms supported by the PGI compilers.
-mcmodel=small
compiler/linker switch to produce small memory model format objects/executables in which both code
(.text) and data (.bss) sections are limited to less than 2GB. This switch is the default and only possible
format for linux86 32-bit executables. This switch is the default format for linux86-64 executables.PGI® User’s Guide
xxiv
Maximum address offset range is 32-bits, and total memory used for OS+Code+Data must be less than
2GB.
-mcmodel=medium
compiler/linker switch to produce medium memory model format objects/executables in which code
sections are limited to less than 2GB, but data sections can be greater than 2GB. This option is supported
only in linux86-64 environments. It must be used to compile any program unit that will be linked in to a
64-bit executable that will use aggregate data sets larger than 2GB and will access data requiring address
offsets greater than 2GB. This option must be used to link any 64-bit executable that will use aggregate
data sets greater than 2GB in size. Executables linked using -mcmodel=medium can incorporate objects
compiled using -mcmodel=small as long as the small objects are from a shared library.
NUMA
A type of multi-processor system architecture in which the memory latency from a given processor to a
given portion of memory can vary, resulting in the possibility for compiler or programming optimizations
to ensure frequently accessed data is "close" to a given processor as determined by memory latency.
osx86
32-bit Apple Mac OS Operating Systems running on an x86 Core 2 or Core 2 Duo processor-based system
with the 32-bit Apple and GNU tools, utilities, and libraries used by the PGI compilers to assemble and link
for 32-bit execution. The PGI Workstation preview supports Mac OS 10.4.9 only.
osx86-64
64-bit Apple Mac OS Operating Systems running on an x64 Core 2 Duo processor-based system with the
64-bit and 32-bit Apple and GNU tools, utilities, and libraries used by the PGI compilers to assemble and
link for either 64- or 32-bit execution. The PGI Workstation preview supports Mac OS 10.4.9 only.
SFU
Windows Services for Unix, a 32-bit-only predecessor of SUA, the Subsystem for Unix Applications. See
SUA.
Shared library
a Linux library of the form libxxx.so containing objects that are dynamically linked into a program at the
time of execution.
SSE
collectively, all SSE extensions supported by the PGI compilers.
SSE1
32-bit IEEE 754 FPU and associated streaming SIMD extensions (SSE) instructions on Pentium III,
AthlonXP* and later 32-bit x86, AMD64 and EM64T compatible CPUs, enabling scalar and packed vector
arithmetic on single-precision floating-point data.
SSE2
64-bit IEEE 754 FPU and associated SSE instructions on P4/Xeon and later 32-bit x86, AMD64 and EM64T
compatible CPUs. SSE2 enables scalar and packed vector arithmetic on double-precision floating-point
data.
SSE3
additional 32-bit and 64-bit SSE instructions to enable more efficient support of arithmetic on complex
floating-point data on 32-bit x86, AMD64 and EM64T compatible CPUs with so-called Prescott NewPreface
xxv
Instructions (PNI), such as Intel IA32 processors with EM64T extensions and newer generation (Revision
E and beyond) AMD64 processors.
SSE4A and ABM
AMD Instruction Set enhancements for the Quad-Core AMD Opteron Processor. Support for these
instructions is enabled by the -tp barcelona or -tp barcelona-64 switch.
SSSE3
an extension of the SSE3 instruction set found on the Intel Core 2.
Static linking
a method of linking:
On Linux, use - to ensure all objects are included in a generated executable at link time. Static linking
causes objects from static library archives of the form libxxx.a to be linked in to your executable, rather
than dynamically linking the corresponding libxxx.so shared library. Static linking of executables linked
using the -mcmodel=medium option is supported.
On Windows, the Windows linker links statically or dynamically depending on whether the libraries on the
link-line are DLL import libraries or static libraries. By default, the static PGI libraries are included on the
link line. To link with DLL versions of the PGI libraries instead of static libraries, use the -Mdll option.
SUA
Subsystem for UNIX-based Applications (SUA) is source-compatibility subsystem for compiling and
running custom UNIX-based applications on a computer running 32-bit or 64-bit Windows server-class
operating system. It provides an operating system for Portable Operating System Interface (POSIX)
processes. SUA supports a package of support utilities (including shells and >300 Unix commands),
case-sensitive file names, and job control. The subsystem installs separately from the Windows kernel to
support UNIX functionality without any emulation.
Win32
any of the 32-bit Microsoft Windows Operating Systems (XP/2000/Server 2003) running on an x86 or x64
processor-based system. On these targets, the PGI compiler products include all of the tools and libraries
needed to build executables for 32-bit Windows systems.
Win64
any of the 64-bit Microsoft Windows Operating Systems (XP Professional /Windows Server 2003 x64
Editions) running on an x64 processor-based system. On these targets, the PGI compiler products include
all of the tools and libraries needed to build executables for 32-bit Windows systems.
Windows
collectively, all Win32 and Win64 platforms supported by the PGI compilers.
x64
collectively, all AMD64 and EM64T processors supported by the PGI compilers.
x86
a processor designed to be binary compatible with i386/i486 and previous generation processors from
Intel* Corporation. Refers collectively to such processors up to and including 32-bit variants.
x87
- 80-bit IEEE stack-based floating-point unit (FPU) and associated instructions on x86-compatible CPUs.PGI® User’s Guide
xxvi
The following table lists the PGI compilers and tools and their corresponding commands:
Table 1. PGI Compilers and Commands
Compiler or Tool Language or Function Command
PGF77 FORTRAN 77 pgf77
PGF95 Fortran 90/95 pgf95
PGHPF High Performance Fortran pghpf
PGCC C ANSI C99 and K&R C pgcc
PGC++ ANSI C++ with cfront features pgcpp (pgCC)
PGDBG Source code debugger pgdbg
PGPROF Performance profiler pgprof
In general, the designation PGF95 is used to refer to The Portland Group’s Fortran 90/95 compiler, and pgf95
is used to refer to the command that invokes the compiler. A similar convention is used for each of the PGI
compilers and tools.
For simplicity, examples of command-line invocation of the compilers generally reference the pgf95
command, and most source code examples are written in Fortran. Usage of the PGF77 compiler, whose
features are a subset of PGF95, is similar. Usage of PGHPF, PGC++, and PGCC ANSI C99 is consistent with
PGF95 and PGF77, but there are command-line options and features of these compilers that do not apply to
PGF95 and PGF77 and vice versa.
There are a wide variety of x86-compatible processors in use. All are supported by the PGI compilers and
tools. Most of these processors are forward-compatible, but not backward-compatible, meaning that code
compiled to target a given processor will not necessarily execute correctly on a previous-generation processor.
The following table provides a partial list, including the most important processor types, along with the
features utilized by the PGI compilers that distinguish them from a compatibility standpoint:
Table 2. Processor Options
Processor Prefetch SSE1 SSE2 SSE3 32-bit 64-bit Scalar FP
Default
AMD Athlon N N N N Y N x87
AMD Athlon XP/MP Y Y N N Y N x87
AMD Athlon64 Y Y Y N Y Y SSE
AMD Opteron Y Y Y N Y Y SSE
AMD Opteron Rev E Y Y Y Y Y Y SSE
AMD Opteron Rev F Y Y Y Y Y Y SSE
AMD Turion Y Y Y Y Y Y SSE
Intel Celeron N N N N Y N x87Preface
xxvii
Processor Prefetch SSE1 SSE2 SSE3 32-bit 64-bit Scalar FP
Default
Intel Pentium II N N N N Y N x87
Intel Pentium III Y Y N N Y N x87
Intel Pentium 4 Y Y Y N Y N SSE
Intel Pentium M Y Y Y N Y N SSE
Intel Centrino Y Y Y N Y N SSE
Intel Pentium 4 EM64T Y Y Y Y Y Y SSE
Intel Xeon EM64T Y Y Y Y Y Y SSE
Intel Core Duo EM64T Y Y Y Y Y Y SSE
Intel Core 2 Duo
EM64T
Y Y Y Y Y Y SSE
In this manual, the convention is to use “x86” to specify the group of processors in the previous table that are
listed as “32-bit” but not “64-bit.” The convention is to use “x64” to specify the group of processors that are
listed as both “32-bit” and “64-bit.” x86 processor-based systems can run only 32-bit operating systems. x64
processor-based systems can run either 32-bit or 64-bit operating systems, and can execute all 32-bit x86
binaries in either case. x64 processors have additional registers and 64-bit addressing capabilities that are
utilized by the PGI compilers and tools when running on a 64-bit operating system. The prefetch, SSE1, SSE2
and SSE3 processor features further distinguish the various processors. Where such distinctions are important
with respect to a given compiler option or feature, it is explicitly noted in this manual.
Note that the default for performing scalar floating-point arithmetic is to use SSE instructions on targets that
support SSE1 and SSE2. See section 2.3.1, Scalar SSE Code Generation, for a detailed discussion of this topic.
Related Publications
The following documents contain additional information related to the x86 and x64 architectures, and the
compilers and tools available from The Portland Group.
• PGI Fortran Reference manual describes the FORTRAN 77, Fortran 90/95, and HPF statements, data
types, input/output format specifiers, and additional reference material related to use of the PGI Fortran
compilers.
• System V Application Binary Interface Processor Supplement by AT&T UNIX System Laboratories, Inc.
(Prentice Hall, Inc.).
• System V Application Binary Interface X86-64 Architecture Processor Supplement, http://www.x86-
64.org/abi.pdf.
• Fortran 95 Handbook Complete ISO/ANSI Reference, Adams et al, The MIT Press, Cambridge, Mass, 1997.
• Programming in VAX Fortran, Version 4.0, Digital Equipment Corporation (September, 1984).
• IBM VS Fortran, IBM Corporation, Rev. GC26-4119.
• The C Programming Language by Kernighan and Ritchie (Prentice Hall).PGI® User’s Guide
xxviii
• C: A Reference Manual by Samuel P. Harbison and Guy L. Steele Jr. (Prentice Hall, 1987).
• The Annotated C++ Reference Manual by Margaret Ellis and Bjarne Stroustrup, AT&T Bell Laboratories,
Inc. (Addison-Wesley Publishing Co., 1990).
• OpenMP Application Program Interface, Version 2.5 May 2005 (OpenMP Architecture Review Board,
1997-2005).1
Chapter 1. Getting Started
This chapter describes how to use the PGI compilers. The command used to invoke a compiler, such as
the pgf95 command, is called a compiler driver. The compiler driver controls the following phases of
compilation: preprocessing, compiling, assembling, and linking. Once a file is compiled and an executable file
is produced, you can execute, debug, or profile the program on your system. Executables produced by the PGI
compilers are unconstrained, meaning they can be executed on any compatible x86 or x64 processor-based
system, regardless of whether the PGI compilers are installed on that system.
Overview
In general, using a PGI compiler involves three steps:
1. Produce a program source code in a file containing a .f extension or another appropriate extension, as
described in “Input Files,” on page 3. This program may be one that you have written or one that you
are modifying.
2. Compile the program using the appropriate compiler command.
3. Execute, debug, or profile the executable file on your system.
You might also want to deploy your application, though this is not a required step.
The PGI compilers allow many variations on these general program development steps. These variations
include the following:
• Stop the compilation after preprocessing, compiling or assembling to save and examine intermediate
results.
• Provide options to the driver that control compiler optimization or that specify various features or
limitations.
• Include as input intermediate files such as preprocessor output, compiler output, or assembler output.
Invoking the Command-level PGI Compilers
To translate and link a Fortran, C, or C++ program, the pgf77, pgf95, pghpf, pgcc, and pgcpp commands do
the following:PGI® User’s Guide
2
1. Preprocess the source text file.
2. Check the syntax of the source text.
3. Generate an assembly language file.
4. Pass control to the subsequent assembly and linking steps.
Example 1.1. Hello program
Let’s look at a simple example of using the PGI compiler to create, compile, and execute a program that prints
hello.
Step 1: Create your program.
For this example, suppose you enter the following simple Fortran program in the file hello.f:
print *, "hello"
end
Step 2: Compile the program.
When you created your program, you called it hello.f. In this example, we compile it from a shell
command prompt using the default pgf95 driver option. Use the following syntax:
PGI$ pgf95 hello.f
PGI$
By default, the executable output is placed in the file a.out, or, on Windows platforms, in a filename based
on the name of the first source or object file on the command line. However, you can use the –o option to
specify an output file name. To place the executable output in the file hello, use this command:
PGI$ pgf95 -o hello hello.f
PGI$
Step 3: Execute the program.
To execute the resulting hello program, simply type the filename at the command prompt and press the Return
or Enter key on your keyboard:
PGI$ hello
hello
PGI$
Command-line Syntax
The compiler command-line syntax, using pgf95 as an example, is:
pgf95 [options] [path]filename [...]
Where:
options
is one or more command-line options, all of which are described in detail in Chapter 2, “Using
Command Line Options”.
path
is the pathname to the directory containing the file named by filename. If you do not specify the path for a
filename, the compiler uses the current directory. You must specify the path separately for each filename
not in the current directory.Chapter 1. Getting Started
3
filename
is the name of a source file, preprocessed source file, assembly-language file, object file, or library to be
processed by the compilation system. You can specify more than one [path]filename.
Command-line Options
The command-line options control various aspects of the compilation process. For a complete alphabetical
listing and a description of all the command-line options, refer to Chapter 2, “Using Command Line
Options”.
The following list provides important information about proper use of command-line options.
• Case is significant for options and their arguments.
• The compiler drivers recognize characters preceded by a hyphen (-) as command-line options. For
example, the –Mlist option specifies that the compiler creates a listing file.
Note
The convention for the text of this manual is to show command-line options using a dash instead of
a hyphen; for example, you see –Mlist.
• The pgcpp command recognizes a group of characters preceded by a plus sign (+) as command-line
options.
• The order of options and the filename is not fixed. That is, you can place options before and after the
filename argument on the command line. However, the placement of some options is significant, such as the
–l option, in which the order of the filenames determines the search order.
Note
If two or more options contradict each other, the last one in the command line takes precedence.
Fortran Directives and C/C++ Pragmas
You can insert Fortran directives and C/C++ pragmas in program source code to alter the effects of certain
command-line options and to control various aspects of the compilation process for a specific routine or a
specific program loop. For more information on Fortran directives and C/C++ pragmas, refer to Chapter 5,
“Using OpenMP” and Chapter 6, “Using Directives and Pragmas”.
Filename Conventions
The PGI compilers use the filenames that you specify on the command line to find and to create input and
output files. This section describes the input and output filename conventions for the phases of the compilation
process.
Input Files
You can specify assembly-language files, preprocessed source files, Fortran/C/C++ source files, object files,
and libraries as inputs on the command line. The compiler driver determines the type of each input file by
examining the filename extensions. The drivers use the following conventions:PGI® User’s Guide
4
filename.f
indicates a Fortran source file.
filename.F
indicates a Fortran source file that can contain macros and preprocessor directives (to be preprocessed).
filename.FOR
indicates a Fortran source file that can contain macros and preprocessor directives (to be preprocessed).
filename.F95
indicates a Fortran 90/95 source file that can contain macros and preprocessor directives (to be
preprocessed).
filename.f90
indicates a Fortran 90/95 source file that is in freeform format.
filename.f95
indicates a Fortran 90/95 source file that is in freeform format.
filename.hpf
indicates an HPF source file.
filename.c
indicates a C source file that can contain macros and preprocessor directives (to be preprocessed).
filename.i
indicates a preprocessed C or C++ source file.
filename.C
indicates a C++ source file that can contain macros and preprocessor directives (to be preprocessed).
filename.cc
indicates a C++ source file that can contain macros and preprocessor directives (to be preprocessed).
filename.s
indicates an assembly-language file.
filename.o
(Linux, Apple, SFU, SUA) indicates an object file.
filename.obj
(Windows systems only) indicates an object file.
filename.a
(Linux, Apple, SFU, SUA) indicates a library of object files.
filename.lib
(Windows systems only) indicates a statically-linked library of object files.
filename.so
(Linux and SFU systems only) indicates a library of shared object files.
filename.dll
(Windows systems only) indicates a dynamically-linked library.Chapter 1. Getting Started
5
filename..objlib
(Apple systems only) indicates a dynamically-linked library.
The driver passes files with .s extensions to the assembler and files with .o, .obj, .so, .dll, .a and .lib extensions
to the linker. Input files with unrecognized extensions, or no extension, are also passed to the linker.
Files with a .F (Capital F) or .FOR suffix are first preprocessed by the Fortran compilers and the output is
passed to the compilation phase. The Fortran preprocessor functions similar to cpp for C/C++ programs, but
is built in to the Fortran compilers rather than implemented through an invocation of cpp. This design ensures
consistency in the preprocessing step regardless of the type or revision of operating system under which you’re
compiling.
Any input files not needed for a particular phase of processing are not processed. For example, if on
the command line you specify an assembly-language file (filename.s) and the –S option to stop before
the assembly phase, the compiler takes no action on the assembly language file. Processing stops after
compilation and the assembler does not run. In this scenario, the compilation must have been completed in
a previous pass which created the .s file. For a complete description of the –S option, refer to the following
section:“Output Files”.
In addition to specifying primary input files on the command line, code within other files can be compiled
as part of include files using the INCLUDE statement in a Fortran source file or the preprocessor
#include directive in Fortran source files that use a .F extension or C and C++ source files.
When linking a program with a library, the linker extracts only those library components that the program
needs. The compiler drivers link in several libraries by default. For more information about libraries, refer to
Chapter 7, “Creating and Using Libraries”.
Output Files
By default, an executable output file produced by one of the PGI compilers is placed in the file a.out, or,
on Windows, in a filename based on the name of the first source or object file on the command line. As the
example in the preceding section shows, you can use the –o option to specify the output file name.
If you use one of the options: –F (Fortran only), –P (C/C++ only), –S or –c, the compiler produces a file
containing the output of the last completed phase for each input file, as specified by the option supplied. The
output file will be a preprocessed source file, an assembly-language file, or an unlinked object file respectively.
Similarly, the –E option does not produce a file, but displays the preprocessed source file on the standard
output. Using any of these options, the –o option is valid only if you specify a single input file. If no errors
occur during processing, you can use the files created by these options as input to a future invocation of any of
the PGI compiler drivers. The following table lists the stop-after options and the output files that the compilers
create when you use these options. It also describes the accepted input files.
Table 1.1. Stop-after Options, Inputs and Outputs
Option Stop after Input Output
–E preprocessing Source files. For Fortran, must have .F
extension.
preprocessed file to
standard outPGI® User’s Guide
6
Option Stop after Input Output
–F preprocessing Source files. Must have .F extension. This
option is not valid for pgcc or pgcpp.
preprocessed file (.f)
–P preprocessing Source files. This option is not valid for pgf77,
pgf95 or pghpf)
preprocessed file (.i)
–S compilation Source files or preprocessed files assembly-language file (.s)
–c assembly Source files, preprocessed files or assemblylanguage files
unlinked object file (.o or
.obj)
none linking Source files, preprocessed files, assemblylanguage files, object files or libraries
executable file (a.out or
.exe)
If you specify multiple input files or do not specify an object filename, the compiler uses the input filenames
to derive corresponding default output filenames of the following form, where filename is the input filename
without its extension:
filename.f
indicates a preprocessed file, if you compiled a Fortran file using the –F option.
filename.i
indicates a prepossedfile, if you compiled using the –P option..
filename.lst
indicates a listing file from the –Mlist option.
filename.o or filename.obj
indicates an object file from the –c option.
filename.s
indicates an assembly-language file from the –S option.
Note
Unless you specify otherwise, the destination directory for any output file is the current working
directory. If the file exists in the destination directory, the compiler overwrites it.
The following example demonstrates the use of output filename extensions.
$ pgf95 -c proto.f proto1.F
This produces the output files proto.o and proto1.o, or, on Windows, proto.obj and proto1.obj all of which
are binary object files. Prior to compilation, the file proto1.F is preprocessed because it has a .F filename
extension.
Fortran, C, and C++ Data Types
The PGI Fortran, C, and C++ compilers recognize scalar and aggregate data types. A scalar data type holds
a single value, such as the integer value 42 or the real value 112.6. An aggregate data type consists of one or
more scalar data type objects, such as an array of integer values.Chapter 1. Getting Started
7
For information about the format and alignment of each data type in memory, and the range of values each
type can have on x86 or x64 processor-based systems running a 32-bit operating system, refer to Chapter 13,
“Fortran, C and C++ Data Types”.
For more information on x86-specific data representation, refer to the System V Application Binary Interface
Processor Supplement by AT&T UNIX System Laboratories, Inc. (Prentice Hall, Inc.).
This manual specifically does not address x64 processor-based systems running a 64-bit operating system,
because the application binary interface (ABI) for those systems is still evolving. For the latest version of this
ABI, see www.x86-64.org/abi.pdf.
Parallel Programming Using the PGI Compilers
The PGI compilers support three styles of parallel programming:
• Automatic shared-memory parallel programs compiled using the –Mconcur option to pgf77, pgf95, pgcc,
or pgcpp — parallel programs of this variety can be run on shared-memory parallel (SMP) systems such as
dual-core or multi-processor workstations.
• OpenMP shared-memory parallel programs compiled using the –mp option to pgf77, pgf95, pgcc, or pgcpp
— parallel programs of this variety can be run on SMP systems. Carefully coded user-directed parallel
programs using OpenMP directives can often achieve significant speed-ups on dual-core workstations
or large numbers of processors on SMP server systems. Chapter 5, “Using OpenMP” contains complete
descriptions of user-directed parallel programming.
• Data parallel shared- or distributed-memory parallel programs compiled using the PGHPF High
Performance Fortran compiler — parallel programs of this variety can be run on SMP workstations or
servers, distributed-memory clusters of workstations, or clusters of SMP workstations or servers. Coding
a data parallel version of an application can be more work than using OpenMP directives, but has the
advantage that the resulting executable is usable on all types of parallel systems regardless of whether
shared memory is available. See the PGHPF User’s Guide for a complete description of how to build and
execute data parallel HPF programs.
In this manual, the first two types of parallel programs are collectively referred to as SMP parallel programs.
The third type is referred to as a data parallel program, or simply as an HPF program.
Some newer CPUs incorporate two or more complete processor cores - functional units, registers, level 1
cache, level 2 cache, and so on - on a single silicon die. These CPUs are known as multi-core processors. For
purposes of HPF, threads, or OpenMP parallelism, these cores function as two or more distinct processors.
However, the processing cores are on a single chip occupying a single socket on a system motherboard. For
purposes of PGI software licensing, a multi-core processor is treated as a single CPU.
Running SMP Parallel Programs
When you execute an SMP parallel program, by default it uses only one processor. To run on more than one
processor, set the NCPUS environment variable to the desired number of processors, subject to a maximum of
four for PGI’s workstation-class products.
You can set this environment variable by issuing the following command in a Windows command prompt
window:PGI® User’s Guide
8
% setenv NCPUS
In a shell command window under csh, issue the following command:
% setenv NCPUS
In sh, ksh, or BASH command window, issue the following command:
% NCPUS=; export NCPUS
Note
If you set NCPUS to a number larger than the number of physical processors, your program may
execute very slowly.
Running Data Parallel HPF Programs
When you execute an HPF program, by default it will use only one processor. If you wish to run on more
than one processor, use the -pghpf -np runtime option. For example, to compile and run the hello.f example
defined above on one processor, you would issue the following commands:
% pghpf -o hello hello.f
Linking:
% hello
hello
%
To execute it on two processors, you would issue the following commands:
% hello -pghpf -np 2
hello
%
Note
If you specify a number larger than the number of physical processors, your program will execute
very slowly.
You still only see a single “hello” printed to your screen. This is because HPF is a single-threaded model,
meaning that all statements execute with the same semantics as if they were running in serial. However,
parallel statements or constructs operating on explicitly distributed data are in fact executed in parallel.
The programmer must manually insert compiler directives to cause data to be distributed to the available
processors. See the PGHPF User’s Guide and The High Performance Fortran Handbook for more details on
constructing and executing data parallel programs on shared-memory or distributed-memory cluster systems
using PGHPF.
Platform-specific considerations
There are nine platforms supported by the PGI Workstation and PGI Server compilers and tools:
• 32-bit Linux - supported on 32-bit Linux operating systems running on either a 32-bit x86 compatible or an
x64 compatible processor.Chapter 1. Getting Started
9
• 64-bit/32-bit Linux - includes all features and capabilities of the 32-bit Linux version, and is also supported
on 64-bit Linux operating systems running on an x64 compatible processor.
• 32-bit Windows - supported on 32-bit Windows operating systems running on either a 32-bit x86
compatible or an x64 compatible processor.
• 64-bit/32-bit Windows - includes all features and capabilities of the 32-bit Windows version, and is also
supported on 64-bit Windows operating systems running an x64 compatible processor.
• 32-bit SFU - supported on 32-bit Windows operating systems running on either a 32-bit x86 compatible or
an x64 compatible processor.
• 32-bit SUA - supported on 32-bit Windows operating systems running on either a 32-bit x86 compatible or
an x64 compatible processor.
• 64-bit/32-bit SUA - includes all features and capabilities of the 32-bit SUA version, and is also supported on
64-bit Windows operating systems running on an x64 compatible processor.
• 32-bit Apple Mac OS X - supported on 32-bit Apple Mac operating systems running on either a 32-bit or 64-
bit Intel-based Mac system.
• 64-bit Apple Mac OS X - supported on 64-bit Apple Mac operating systems running on a 64-bit Intel-based
Mac system.
The following sections describe the specific considerations required to use the PGI compilers on the various
platforms: Linux, Windows, and Apple Mac OS X.
Using the PGI Compilers on Linux
Linux Header Files
The Linux system header files contain many GNU gcc extensions. PGI supports many of these extensions,
thus allowing the PGCC C and C++ compilers to compile most programs that the GNU compilers can
compile. A few header files not interoperable with the PGI compilers have been rewritten and are included
in $PGI/linux86/include. These files are: sigset.h, asm/byteorder.h, stddef.h, asm/
posix_types.h and others. Also, PGI’s version of stdarg.h supports changes in newer versions of Linux.
If you are using the PGCC C or C++ compilers, please make sure that the supplied versions of these include
files are found before the system versions. This will happen by default unless you explicitly add a –I option that
references one of the system include directories.
Running Parallel Programs on Linux
You may encounter difficulties running auto-parallel or OpenMP programs on Linux systems when the
per-thread stack size is set to the default (2MB). If you have unexplained failures, please try setting the
environment variable OMP_STACK_SIZE to a larger value, such as 8MB. This can be accomplished with the
command in csh:
% setenv OMP_STACK_SIZE 8M
in bash, sh, or ksh, use:
% OMP_STACK_SIZE=8M; export OMP_STACK_SIZEPGI® User’s Guide
10
If your program is still failing, you may be encountering the hard 8 MB limit on main process stack sizes in
Linux. You can work around the problem by issuing the following command in csh:
% limit stacksize unlimited
in bash, sh, or ksh, use:
% ulimit -s unlimited
Using the PGI Compilers on Windows
BASH Shell Environment
On Windows platforms, the tools that ship with the PGI Workstation or PGI Server command-level compilers
include a full-featured shell command environment. After installation, you should have a PGI icon on your
Windows desktop. Double-left-click on this icon to cause an instance of the BASH command shell to appear
on your screen. Working within BASH is very much like working within the sh or ksh shells on a Linux system,
but in addition BASH has a command history feature similar to csh and several other unique features. Shell
programming is fully supported. A complete BASH User’s Guide is available through the PGI online manual set.
Select “PGI Workstation” under Start->Programs and double-left-click on the documentation icon to see the
online manual set. You must have a web browser installed on your system in order to read the online manuals.
The BASH shell window is pre-initialized for usage of the PGI compilers and tools, so there is no need to set
environment variables or modify your command path when the command window comes up. In addition to the
PGI compiler commands referenced above, within BASH you have access to over 100 common commands and
utilities, including but not limited to the following:
vi emacs make
tar / untar gzip / gunzip ftp
sed grep / egrep / fgrep awk
cat cksum cp
date diff du
find kill ls
more / less mv printenv / env
rm / rmdir touch wc
If you are familiar with program development in a Linux environment, editing, compiling, and executing
programs within BASH will be very comfortable. If you have not previously used such an environment, you
should take time to familiarize yourself with either the vi or emacs editors and with makefiles. The emacs
editor has an extensive online tutorial, which you can start by bringing up emacs and selecting the appropriate
option under the pull-down help menu. You can get a thorough introduction to the construction and use of
makefiles through the online Makefile User’s Guide.
For library compatibility, PGI provides versions of ar and ranlib that are compatible with native Windows
object-file formats. For more information on these commands, refer to “Creating and Using Static Libraries on
Windows,” on page 79.Chapter 1. Getting Started
11
Windows Command Prompt
The PGI Workstation entry in the Windows Start menu contains a submenu titled PGI Workstation Tools.
This submenu contains a shortcut labeled PGI Command Prompt (32-bit). The shortcut is used to launch a
Windows command shell using an environment pre-initialized for the use of the 32-bit PGI compilers and
tools. On x64 systems, a second shortcut labeled PGI Command Prompt (64-bit) will also be present. This
shortcut launches a Windows command shell using an environment pre-initialized for the use of the 64-bit PGI
compilers and tools.
Using the PGI Compilers on SUA and SFU
Subsystem for Unix Applications (SUA and SFU)
Subsystem for Unix Applications (SUA) is a source-compatibility subsystem for running Unix applications on
32-bit and 64-bit Windows server-class operating systems. PGI Workstation for Windows includes compilers
and tools for SUA and its 32-bit-only predecessor, Services For Unix (SFU).
SUA provides an operating system for POSIX processes. There is a package of support utilities available for
download from Microsoft that provides a more complete Unix environment, including features like shells,
scripting utilities, a telnet client, development tools, and so on.
SUA/SFU Header Files
The SUA/SFU system header files contain numerous non-standard extensions. PGI supports many of these
extensions, thus allowing the PGCC C and C++ compilers to compile most programs that the GNU compilers
can compile. A few header files not interoperable with the PGI compilers have been rewritten and are included
in $PGI/sua32/include or $PGI/sua64/include. These files are: stdarg.h, stddef.h, and others.
If you are using the PGCC C or C++ compilers, please make sure that the supplied versions of these include
files are found before the system versions. This happens by default unless you explicitly add a –I option that
references one of the system include directories.
Running Parallel Programs on SUA and SFU
You may encounter difficulties running auto-parallel or OpenMP programs on SUA/SFU systems when the
per-thread stack size is set to the default (2MB). If you have unexplained failures, please try setting the
environment variable OMP_STACK_SIZE to a larger value, such as 8MB. This can be accomplished with the
command:
in csh:
% setenv OMP_STACK_SIZE 8M
in bash, sh, or ksh.
% OMP_STACK_SIZE=8M; export OMP_STACK_SIZE
Using the PGI Compilers on Mac OS X
Mac OS X Header FilesPGI® User’s Guide
12
The Mac OS X header files contain numerous non-standard extensions. PGI supports many of these extensions,
thus allowing the PGCC C and C++ compilers to compile most programs that the GNU compilers can compile.
A few header files not interoperable with the PGI compilers have been rewritten and are included in $PGI/
sua32/include or $PGI/sua64/include. These files are: stdarg.h, stddef.h, and others.
If you are using the PGCC C or C++ compilers, please make sure that the supplied versions of these include
files are found before the system versions. This will happen by default unless you explicitly add a –I option that
references one of the system include directories.
Running Parallel Programs on Mac OS
You may encounter difficulties running auto-parallel or OpenMP programs on Mac OS X systems when the
per-thread stack size is set to the default (8MB). If you have unexplained failures, please try setting the
environment variable OMP_STACK_SIZE to a larger value, such as 16MB. This can be accomplished with the
following command:
in csh:
% setenv OMP_STACK_SIZE 16M
in bash, sh, or ksh.
% OMP_STACK_SIZE=16M; export OMP_STACK_SIZE
Site-specific Customization of the Compilers
If you are using the PGI compilers and want all your users to have access to specific libraries or other files,
there are special files that allow you to customize the compilers for your site.
Using siterc Files
The PGI compiler drivers utilize a file named siterc to enable site-specific customization of the behavior of
the PGI compilers. The siterc file is located in the bin subdirectory of the PGI installation directory. Using
siterc, you can control how the compiler drivers invoke the various components in the compilation tool
chain.
Using User rc Files
In addition to the siterc file, user rc files can reside in a given user’s home directory, as specified by the user’s
HOME environment variable. You can use these files to control the respective PGI compilers. All of these files
are optional.
On Linux and SUA these files are named .mypgf77rc, .mypgf90rc, .mypgccrc, .mypgcpprc, and
.mypghpfrc.
On native windows, these files are named mypgf77rc, mypgf95rc, mypgccrc, mypgcpprc, and
mypghpfrc.
On Windows, these files are named mypgf77rc and mypgf95rc.
The following examples show how these rc files can be used to tailor a given installation for a particular
purpose.Chapter 1. Getting Started
13
Table 1.2. Examples of Using siterc and User rc Files
To do this... Add the line shown to the indicated file
Make the libraries found in the
following location available to all
linux86-64 compilations.
/opt/newlibs/64
set SITELIB=/opt/newlibs/64;
to /opt/pgi/linux86-64/7.1/bin/siterc
Make the libraries found in the
following location available to all
linux86 compilations.
/opt/newlibs/32
set SITELIB=/opt/newlibs/32;
to /opt/pgi/linux86/7.1/bin/siterc
Add the following new library path to all
linux86-64 compilations.
/opt/local/fast
append SITELIB=/opt/local/fast;
to /opt/pgi/linux86-64/7.1/bin/siterc
Make the following include path
available to all compilations;
-I/opt/acml/include
set SITEINC=/opt/acml/include;
to /opt/pgi/linux86/7.1/bin/siterc and /
opt/pgi/linux86-64/7.1/bin/siterc
Change –Mmpi to link in the following
with linux86-64 compilations.
/opt/mympi/64/libmpix.a
set MPILIBDIR=/opt/mympi/64;
set MPILIBNAME=mpix;
to /opt/pgi/linux86-64/7.1/bin/siterc;
Have linux86-64 compilations always
add
–DIS64BIT –DAMD
set SITEDEF=IS64BIT AMD;
to /opt/pgi/linux86-64/7.1/bin/siterc
Build an F90 executable for linux86-
64 or linux86 that resolves PGI shared
objects in the relative directory
./REDIST
set RPATH=./REDIST ;
to ~/.mypgf95rc
Note
This only affects the behavior of PGF95 for the
given user.
Common Development Tasks
Now that you have a brief introduction to the compiler, let’s look at some common development tasks that you
might wish to perform.
• When you compile code you can specify a number of options on the command line that define specific
characteristics related to how the program is compiled and linked, typically enhancing or overriding the
default behavior of the compiler. For a list of the most common command line options and information on
all the command line options, refer to Chapter 2, “Using Command Line Options”.
• Code optimization and parallelization allow you to organize your code for efficient execution. While possibly
increasing compilation time and making the code more difficult to debug, these techniques typicallyPGI® User’s Guide
14
produce code that runs significantly faster than code that does not use them. For more information on
optimization and parallelization, refer to Chapter 3, “Using Optimization & Parallelization”.
• Function inlining, a special type of optimization, replaces a call to a function or a subroutine with the body
of the function or subroutine. This process can speed up execution by eliminating parameter passing and
the function or subroutine call and return overhead. In addition, function inlining allows the compiler
to optimize the function with the rest of the code. However, function inlining may also result in much
larger code size with no increase in execution speed. For more information on function inlining, refer to
Chapter 4, “Using Function Inlining”.
• Directives and pragmas allow users to place hints in the source code to help the compiler generate
better assembly code. You typically use directives and pragmas to control the actions of the compiler in a
particular portion of a program without affecting the program as a whole. You place them in your source
code where you want them to take effect. A directive or pragma typically stays in effect from the point where
included until the end of the compilation unit or until another directive or pragma changes its status. For
more information on directives and pragmas, refer to Chapter 5, “Using OpenMP”and Chapter 6, “Using
Directives and Pragmas”.
• A library is a collection of functions or subprograms used to develop software. Libraries contain "helper"
code and data, which provide services to independent programs, allowing code and data to be shared and
changed in a modular fashion. The functions and programs in a library are grouped for ease of use and
linking. When creating your programs, it is often useful to incorporate standard libraries or proprietary
ones. For more information on this topic, refer to Chapter 7, “Creating and Using Libraries”.
• Environment variables define a set of dynamic values that can affect the way running processes behave on a
computer. It is often useful to use these variables to set and pass information that alters the default behavior
of the PGI compilers and the executables which they generate. For more information on these variables,
refer to Chapter 8, “ Using Environment Variables”.
• Deployment, though possibly an infrequent task, can present some unique issues related to concerns
of porting the code to other systems. Deployment, in this context, involves distribution of a specific file
or set of files that are already compiled and configured. The distribution must occur in such a way that
the application executes accurately on another system which may not be configured exactly the same as
the system on which the code was created. For more information on what you might need to know to
successfully deploy your code, refer to Chapter 9, “Distributing Files - Deployment”.
• An intrinsic is a function available in a given language whose implementation is handled specially by the
compiler. Intrinsics make using processor-specific enhancements easier because they provide a C/C++
language interface to assembly instructions. In doing so, the compiler manages details that the user would
normally have to be concerned with, such as register names, register allocations, and memory locations
of data. For C/C++ programs, PGI provides support for MMX and SSE/SSE2/SSE3 intrinsics. For more
information on these intrinsics, refer to Chapter 20, “C/C++ MMX/SSE Inline Intrinsics”.15
Chapter 2. Using Command Line
Options
A command line option allows you to control specific behavior when a program is compiled and linked. This
chapter describes the syntax for properly using command-line options and provides a brief overview of a few
of the more common options.
Note
For a complete list of command-line options, their descriptions and use, refer to Chapter 15,
“Command-Line Options Reference,” on page 163.
Command Line Option Overview
Before looking at all the command-line options, first become familiar with the syntax for these options. There
are a large number of options available to you, yet most users only use a few of them. So, start simple and
progress into using the more advanced options.
By default, the PGI 7.1 compilers generate code that is optimized for the type of processor on which
compilation is performed, the compilation host. Before adding options to your command-line, review the
sections“Help with Command-line Options,” on page 16 and “Frequently-used Options,” on page 19.
Command-line Options Syntax
On a command-line, options need to be preceded by a hyphen (-). If the compiler does not recognize an
option, it passes the option to the linker.
This document uses the following notation when describing options:
[item]
Square brackets indicate that the enclosed item is optional.
{item | item}
Braces indicate that you must select one and only one of the enclosed items. A vertical bar (|) separates
the choices.PGI® User’s Guide
16
...
Horizontal ellipses indicate that zero or more instances of the preceding item are valid.
NOTE
Some options do not allow a space between the option and its argument or within an argument. When
applicable, the syntax section of the option description in Chapter 15, “Command-Line Options
Reference,” on page 163 contains this information.
Command-line Suboptions
Some options accept several suboptions. You can specify these suboptions either by using the full option
statement multiple times or by using a comma-separated list for the suboptions.
The following two command lines are equivalent:
pgf95 -Mvect=sse -Mvect=noaltcode
pgf95 -Mvect=sse,noaltcode
Command-line Conflicting Options
Some options have an opposite or negated counterpart. For example, both–Mvect and –Mnovect are
available. –Mvect enables vectorization and –Mnovect disables it. If you used both of these commands on a
command line, they would conflict.
Note
Rule: When you use conflicting options on a command line, the last encountered option takes
precedence over any previous one.
This rule is important for a number of reasons.
• Some options, such as –fast, include other options. Therefore, it is possible for you to be unaware that
you have conflicting options.
• You can use this rule to create makefiles that apply specific flags to a set of files, as shown in Example 2.1.
Example 2.1. Makefiles with Options
In this makefile, CCFLAGS uses vectorization. CCNOVECTFLAGS uses the flags defined for CCFLAGS but disables
vectorization.
CCFLAGS=c -Mvect=sse
CCNOVECTFLAGS=$(CCFLAGS) -Mnovect
Help with Command-line Options
If you are just getting started with the PGI compilers and tools, it is helpful to know which options are
available, when to use them, and which options most users find effective.Chapter 2. Using Command Line Options
17
Using –help
The –help option is useful because it provides information about all options supported by a given compiler.
You can use –help in one of three ways:
• Use –help with no parameters to obtain a list of all the available options with a brief one-line description
of each.
• Add a parameter to –help to restrict the output to information about a specific option. The syntax for this
usage is this:
–help
For example, suppose you use the following command to restrict the output to information about the -
fast option:
pgf95 -help -fast
The output you see is similar to this:
-fast Common optimizations; includes -O2 -Munroll=c:1 -Mnoframe -Mlre
In the following example, usage information for –help shows how groups of options can be listed or
examined according to function
$ pgf95 -help -help
-help[=groups|asm|debug|language|linker|opt|other|
overall|phase|prepro|suffix|switch|target|variable]
Show compiler switches
• Add a parameter to –help to restrict the output to a specific set of options or to a building process. The
syntax for this usage is this:
-help=
The previous output from the command pgf95 -help -help shows the available subgroups. For
example, you can use the following command to restrict the output to information about options related to
debug information generation.
pgf95 -help=debug
The output you see is similar to this:
Debugging switches:
-M[no]bounds Generate code to check array bounds
-Mchkfpstk Check consistency of floating point stack at subprogram calls
(32-bit only)
Note: This switch only works on 32-bit. On 64-bit, the switch is ignored.
-Mchkstk Check for sufficient stack space upon subprogram entry
-Mcoff Generate COFF format object
-Mdwarf1 Generate DWARF1 debug information with -g
-Mdwarf2 Generate DWARF2 debug information with -g
-Mdwarf3 Generate DWARF3 debug information with -g
-Melf Generate ELF format object
-g Generate information for debugger
-gopt Generate information for debugger without disabling
optimizationsPGI® User’s Guide
18
For a complete description of subgroups, refer to “–help ,” on page 178.
Getting Started with Performance
One of top priorities of most users is performance and optimization. This section provides a quick overview of
a few of the command-line options that are useful in improving performance.
Using –fast and –fastsse Options
PGI compilers implement a wide range of options that allow users a fine degree of control on each
optimization phase. When it comes to optimization of code, the quickest way to start is to use –fast and
–fastsse. These options create a generally optimal set of flags for targets that support SSE/SSE2 capability.
They incorporate optimization options to enable use of vector streaming SIMD (SSE/SSE2) instructions for
64-bit targets. They enable vectorization with SSE instructions, cache alignment, and SSE arithmetic to flush to
zero mode.
Note
The contents of the –fast and –fastsse options are host-dependent. Further, you should use these
options on both compile and link command lines.
• –fast and –fastsse typically include these options:
–O2 Specifies a code optimization level of 2.
–Munroll=c:1 Unrolls loops, executing multiple instances of the loop during each
iteration.
–Mnoframe Indicates to not generate code to set up a stack frame.
–Mlre Indicates loop-carried redundancy elimination.
• These additional options are also typically available when using –fast for 64-bit targets and when using
–fastsse for both 32- and 64-bit targets:
–Mvect=sse Generates SSE instructions.
–Mscalarsse Generates scalar SSE code with xmm registers; implies –Mflushz.
–Mcache_align Aligns long objects on cache-line boundaries.
–Mflushz Sets SSE to flush-to-zero mode.
Note
For best performance on processors that support SSE instructions, use the PGF95 compiler, even for
FORTRAN 77 code, and the –fast option.
To see the specific behavior of –fast for your target, use the following command:
pgf95 -help -fastChapter 2. Using Command Line Options
19
Other Performance-related Options
While –fast and -fastsse are options designed to be the quickest route to best performance, they are
limited to routine boundaries. Depending on the nature and writing style of the source code, the compiler
often can perform further optimization by knowing the global context of usage of a given routine. For instance,
determining the possible value range of actual parameters of a routine could enable a loop to be vectorized;
similarly, determining static occurrence of calls helps to decide which routine is beneficial to inline.
These types of global optimizations are under control of Inter Procedural Analysis (IPA) in PGI compilers.
Option -Mipa enables Inter Procedural Analysis. -Mpi=fast is the recommended option to get best
performances for global optimization. You can also add the suboption inline to enable automatic global
inlining across file. You might consider using –Mipa=fast,inline. This option for inter-procedural
analysis and global optimization can improve performance.
You may also be able to obtain further performance improvements by experimenting with the individual
–Mpgflag options detailed in the section“–M Options by Category,” on page 219. These options include
–Mvect, –Munroll, –Minline, –Mconcur, and –Mpfi/–Mpfo. However, performance improvements
using these options are typically application- and system-dependent. It is important to time your application
carefully when using these options to ensure no performance degradations occur.
For more information on optimization, refer to Chapter 3, “Using Optimization & Parallelization,” on page
21. For specific information about these options, refer to “–M Optimization Controls,” on page
229.
Targeting Multiple Systems; Using the -tp Option
The –tp option allows you to set the target architecture. By default, the PGI compiler uses all supported
instructions wherever possible when compiling on a given system. As a result, executables created on a given
system may not be usable on previous generation systems. For example, executables created on a Pentium 4
may fail to execute on a Pentium III or Pentium II.
Processor-specific optimizations can be specified or limited explicitly by using the -tp option. Thus, it is
possible to create executables that are usable on previous generation systems. With the exception of k8-64, k8-
64e, p7-64, and x64, any of these sub-options are valid on any x86 or x64 processor-based system. The k8-64,
k8-64e, p7-64 and x64 options are valid only on x64 processor-based systems
For more information about the -tp option, refer to “–tp [,target...] ,” on page 202.
Frequently-used Options
In addition to overall performance, there are a number of other options that many users find useful when
getting started. The following table provides a brief summary of these options.
For more information on these options, refer to the complete description of each option available in
Chapter 15, “Command-Line Options Reference,” on page 163. Also, there are a number of suboptions
available with each of the –M options listed. For more information on those options, refer to “–M Options by
Category”.PGI® User’s Guide
20
Table 2.1. Commonly Used Command Line Options
Option Description
–fast or –fastsse These options create a generally optimal set of flags for targets that
support SSE/SSE2 capability. They incorporate optimization options
to enable use of vector streaming SIMD instructions (64-bit targets)
and enable vectorization with SEE instructions, cache aligned and
flushz.
–g Instructs the compiler to include symbolic debugging information in
the object module.
–gopt Instructs the compiler to include symbolic debugging information
in the object file, and to generate optimized code identical to that
generated when –g is not specified.
–help Provides information about available options.
–mcmodel=medium Enables medium=model core generation for 64-bit targets; useful
when the data space of the program exceeds 4GB.
–Mconcur Instructs the compiler to enable auto-concurrentization of loops. If
specified, the compiler uses multiple processors to execute loops
that it determines to be parallelizable; thus, loop iterations are split
to execute optimally in a multithreaded execution context.
–Minfo Instructs the compiler to produce information on standard error.
–Minline Passes options to the function inliner.
–Mipa=fast,inline Enables interprocedural analysis and optimization. Also enables
automatic procedure inlining.
–Mneginfo Instructs the compiler to produce information on standard error.
–Mpfi and –Mpfo Enable profile feedback driven optimizations.
–Mkeepasm Keeps the generated assembly files.
–Munroll Invokes the loop unroller to unroll loops, executing multiple
instances of the loop during each iteration. This also sets the
optimization level to 2 if the level is set to less than 2, or if no –O or
–g options are supplied.
–M[no]vect Enables/Disables the code vectorizer.
--[no_]exceptions Removes exception handling from user code.
–o Names the output file.
–O Specifies code optimization level where is 0, 1, 2, 3, or 4.
–tp [,target...] Specify the type(s) of the target processor(s) to enable generation of
PGI Unified Binary executables.21
Chapter 3. Using Optimization &
Parallelization
Source code that is readable, maintainable, and produces correct results is not always organized for efficient
execution. Normally, the first step in the program development process involves producing code that executes
and produces the correct results. This first step usually involves compiling without much worry about
optimization. After code is compiled and debugged, code optimization and parallelization become an issue.
Invoking one of the PGI compiler commands with certain options instructs the compiler to generate optimized
code. Optimization is not always performed since it increases compilation time and may make debugging
difficult. However, optimization produces more efficient code that usually runs significantly faster than code
that is not optimized.
The compilers optimize code according to the specified optimization level. Using the –O, –Mvect, –Mipa,
and –Mconcur, you can specify the optimization levels. In addition, you can use several –M switches
to control specific types of optimization and parallelization.
This chapter describes the optimization options displayed in the following list.
–fast –Mpfi –Mvect
–Mconcur –Mpfo –O
–Mipa=fast –Munroll
This chapter also describes how to choose optimization options to use with the PGI compilers. This overview
will help if you are just getting started with one of the PGI compilers, or wish to experiment with individual
optimizations. Complete specifications of each of these options is available in Chapter 15, “Command-Line
Options Reference”.
Overview of Optimization
In general, optimization involves using transformations and replacements that generate more efficient
code. This is done by the compiler and involves replacements that are independent of the particular target
processor’s architecture as well as replacements that take advantage of the x86 or x64 architecture, instruction
set and registers. For the discussion in this and the following chapters, optimization is divided into the
following categories:PGI® User’s Guide
22
Local Optimization
This optimization is performed on a block-by-block basis within a program’s basic blocks. A basic block is
a sequence of statements in which the flow of control enters at the beginning and leaves at the end without
the possibility of branching, except at the end. The PGI compilers perform many types of local optimization
including: algebraic identity removal, constant folding, common sub-expression elimination, redundant load
and store elimination, scheduling, strength reduction, and peephole optimizations.
Global Optimization
This optimization is performed on a program unit over all its basic blocks. The optimizer performs controlflow and data-flow analysis for an entire program unit. All loops, including those formed by IFs and GOTOs,
are detected and optimized. Global optimization includes: constant propagation, copy propagation, dead store
elimination, global register allocation, invariant code motion, and induction variable elimination.
Loop Optimization: Unrolling, Vectorization, and Parallelization
The performance of certain classes of loops may be improved through vectorization or unrolling options.
Vectorization transforms loops to improve memory access performance and make use of packed SSE
instructions which perform the same operation on multiple data items concurrently. Unrolling replicates the
body of loops to reduce loop branching overhead and provide better opportunities for local optimization,
vectorization and scheduling of instructions. Performance for loops on systems with multiple processors may
also improve using the parallelization features of the PGI compilers.
Interprocedural Analysis (IPA) and Optimization
Interprocedural analysis (IPA) allows use of information across function call boundaries to perform
optimizations that would otherwise be unavailable. For example, if the actual argument to a function is in fact
a constant in the caller, it may be possible to propagate that constant into the callee and perform optimizations
that are not valid if the dummy argument is treated as a variable. A wide range of optimizations are enabled
or improved by using IPA, including but not limited to data alignment optimizations, argument removal,
constant propagation, pointer disambiguation, pure function detection, F90/F95 array shape propagation, data
placement, vestigial function removal, automatic function inlining, inlining of functions from pre-compiled
libraries, and interprocedural optimization of functions from pre-compiled libraries.
Function Inlining
This optimization allows a call to a function to be replaced by a copy of the body of that function. This
optimization will sometimes speed up execution by eliminating the function call and return overhead. Function
inlining may also create opportunities for other types of optimization. Function inlining is not always beneficial.
When used improperly it may increase code size and generate less efficient code.
Profile-Feedback Optimization (PFO)
Profile-feedback optimization (PFO) makes use of information from a trace file produced by specially
instrumented executables which capture and save information on branch frequency, function and subroutine
call frequency, semi-invariant values, loop index ranges, and other input data dependent information that
can only be collected dynamically during execution of a program. By definition, use of profile-feedbackChapter 3. Using Optimization & Parallelization
23
optimization is a two-phase process: compilation and execution of a specially-instrumented executable,
followed by a subsequent compilation which reads a trace file generated during the first phase and uses the
information in that trace file to guide compiler optimizations.
Getting Started with Optimizations
Your first concern should be getting your program to execute and produce correct results. To get your
program running, start by compiling and linking without optimization. Use the optimization level –O0 or select
–g to perform minimal optimization. At this level, you will be able to debug your program easily and isolate any
coding errors exposed during porting to x86 or x64 platforms.
If you want to get started quickly with optimization, a good set of options to use with any of the PGI compilers
is –fast –Mipa=fast. For example:
$ pgf95 -fast -Mipa=fast prog.f
For all of the PGI Fortran, C, and C++ compilers, the –fast, –Mipa=fast options generally produce code
that is well-optimized without the possibility of significant slowdowns due to pathological cases.
The –fast option is an aggregate option that includes a number of individual PGI compiler options;
which PGI compiler options are included depends on the target for which compilation is performed. The
–Mipa=fast option invokes interprocedural analysis including several IPA suboptions.
For C++ programs, add -Minline=levels:10 --no_exceptions:
$ pgcpp -fast -Mipa=fast -Minline=levels:10 --no_exceptions prog.cc
Note
A C++ program compiled with --no_exceptions will fail if the program uses exception handling.
By experimenting with individual compiler options on a file-by-file basis, further significant performance gains
can sometimes be realized. However, depending on the coding style, individual optimizations can sometimes
cause slowdowns, and must be used carefully to ensure performance improvements. In addition to -fast, the
optimization flags most likely to further improve performance are -O3, -Mpfi, -Mpfo, -Minline, and on
targets with multiple processors -Mconcur.
In addition, the –Msafeptr option can significantly improve performance of C/C++ programs in which there
is known to be no pointer aliasing. However, for obvious reasons this command-line option must be used
carefully.
Three other options which are extremely useful are -help, -Minfo, and -dryrun.
–help
As described in “Help with Command-line Options,” on page 16, you can see a specification of any commandline option by invoking any of the PGI compilers with -help in combination with the option in question,
without specifying any input files.
For example:
$ pgf95 -help -O
Reading rcfile /usr/pgi/linux86-64/7.0/bin/.pgf95rcPGI® User’s Guide
24
-O[] Set optimization level, -O0 to -O4, default -O2
Or you can see the full functionality of -help itself, which can return information on either an individual
option or groups of options; type:
$ pgf95 -help -help
Reading rcfile /usr/pgi_rel/linux86-64/7.0/bin/.pgf95rc
-help[=groups|asm|debug|language|linker|opt|other|overall|
phase|prepro|suffix|switch|target|variable]
–Minfo
You can use the -Minfo option to display compile-time optimization listings. When this option is used, the
PGI compilers issue informational messages to stderr as compilation proceeds. From these messages, you
can determine which loops are optimized using unrolling, SSE instructions, vectorization, parallelization,
interprocedural optimizations and various miscellaneous optimizations. You can also see where and whether
functions are inlined.
You can use the -Mneginfo option to display informational messages listing why certain optimizations are
inhibited.
For more information on -Minfo, refer to “–M Optimization Controls,” on page 229
–dryrun
The –dryrun option can be useful as a diagnostic tool if you need to see the steps used by the compiler driver
to preprocess, compile, assemble and link in the presence of a given set of command line inputs. When you
specify the –dryrun option, these steps will be printed to stderr but are not actually performed. For example,
you can use this option to inspect the default and user-specified libraries that are searched during the link
phase, and the order in which they are searched by the linker.
The remainder of this chapter describes the –0 options, the loop unroller option –Munroll, the vectorizer
option –Mvect, the auto-parallelization option –Mconcur, the interprocedural analysis optimization –Mipa,
and the profile-feedback instrumentation (–Mpfi) and optimization (–Mpfo) options. You should be able to
get very near optimal compiled performance using some combination of these switches.
Local and Global Optimization using -O
Using the PGI compiler commands with the –Olevel option (the capital O is for Optimize), you can specify any
of the following optimization levels:
–O0
Level zero specifies no optimization. A basic block is generated for each language statement.
–O1
Level one specifies local optimization. Scheduling of basic blocks is performed. Register allocation is
performed.
–O2
Level two specifies global optimization. This level performs all level-one local optimization as well as leveltwo global optimization. If optimization is specified on the command line without a level, level 2 is the
default.Chapter 3. Using Optimization & Parallelization
25
–O3
Level three specifies aggressive global optimization. This level performs all level-one and level-two
optimizations and enables more aggressive hoisting and scalar replacement optimizations that may or may
not be profitable.
–O4
Level four performs all level-one, level-two, and level-three optimizations and enables hoisting of guarded
invariant floating point expressions.
Note
If you use the -O option to specify optimization and do not specify a level, then level two optimization
(-O2) is the default.
Level-zero optimization specifies no optimization (–O0). At this level, the compiler generates a basic block for
each statement. Performance will almost always be slowest using this optimization level. This level is useful for
the initial execution of a program. It is also useful for debugging, since there is a direct correlation between
the program text and the code generated.
Level-one optimization specifies local optimization (–O1). The compiler performs scheduling of basic blocks
as well as register allocation. Local optimization is a good choice when the code is very irregular, such as code
that contains many short statements containing IF statements and does not contain loops (DO or DO WHILE
statements). Although this case rarely occurs, for certain types of code, this optimization level may perform
better than level-two (–O2).
The PGI compilers perform many different types of local optimizations, including but not limited to:
- Algebraic identity removal - Peephole optimizations
- Constant folding - Redundant load and store elimination
- Common subexpression elimination - Strength reductions
- Local register optimization
Level-two optimization (–O2 or –O) specifies global optimization. The –fast option generally will specify
global optimization; however, the –fast switch varies from release to release, depending on a reasonable
selection of switches for any one particular release. The –O or –O2 level performs all level-one local
optimizations as well as global optimizations. Control flow analysis is applied and global registers are allocated
for all functions and subroutines. Loop regions are given special consideration. This optimization level is a
good choice when the program contains loops, the loops are short, and the structure of the code is regular.
The PGI compilers perform many different types of global optimizations, including but not limited to:
- Branch to branch elimination - Global register allocation
- Constant propagation - Invariant code motion
- Copy propagation - Induction variable elimination
- Dead store eliminationPGI® User’s Guide
26
You can explicitly select the optimization level on the command line. For example, the following command line
specifies level-two optimization which results in global optimization:
$ pgf95 -O2 prog.f
Specifying –O on the command-line without a level designation is equivalent to –O2. The default optimization
level changes depending on which options you select on the command line. For example, when you select the
–g debugging option, the default optimization level is set to level-zero (–O0). However, you can use the -gopt
option to generate debug information without perturbing optimization if you need to debug optimized code.
Refer to “Default Optimization Levels,” on page 42 for a description of the default levels.
As noted above, the –fast option includes –O2 on all x86 and x64 targets. If you wish to override this with
–O3 while maintaining all other elements of –fast, simply compile as follows:
$ pgf95 -fast -O3 prog.f
Scalar SSE Code Generation
For all processors prior to Intel Pentium 4 and AMD Opteron/Athlon64, for example Intel Pentium III and
AMD AthlonXP/MP processors, scalar floating-point arithmetic as generated by the PGI Workstation compilers
is performed using x87 floating-point stack instructions. With the advent of SSE/SSE2 instructions on Intel
Pentium 4/Xeon and AMD Opteron/Athlon64, it is possible to perform all scalar floating-point arithmetic using
SSE/SSE2 instructions. In most cases, this is beneficial from a performance standpoint.
The default on 32-bit Intel Pentium II/III (–tp p6, –tp piii, etc.) or AMD AthlonXP/MP (–tp k7) is to use x87
instructions for scalar floating-point arithmetic. The default on Intel Pentium 4/Xeon or Intel EM64T running a
32-bit operating system (–tp p7), AMD Opteron/Athlon64 running a 32-bit operating system (–tp k8-32), or
AMD Opteron/Athlon64 or Intel EM64T processors running a 64-bit operating system (–tp k8-64 and –tp p7-
64 respectively) is to use SSE/SSE2 instructions for scalar floating-point arithmetic. The only way to override
this default on AMD Opteron/Athlon64 or Intel EM64T processors running a 64-bit operating system is to
specify an older 32-bit target (for example –tp k7 or –tp piii).
Note
There can be significant arithmetic differences between calculations performed using x87 instructions
versus SSE/SSE2.
By default, all floating-point data is promoted to IEEE 80-bit format when stored on the x87 floating-point
stack, and all x87 operations are performed register-to-register in this same format. Values are converted
back to IEEE 32-bit or IEEE 64-bit when stored back to memory (for REAL/float and DOUBLE PRECISION/
double data respectively). The default precision of the x87 floating-point stack can be reduced to IEEE 32-bit
or IEEE 64-bit globally by compiling the main program with the –pc {32 | 64} option to the PGI Workstation
compilers, which is described in detail in Chapter 2, “Using Command Line Options”. However, there is no
way to ensure that operations performed in mixed precision will match those produced on a traditional loadstore RISC/UNIX system which implements IEEE 64-bit and IEEE 32-bit registers and associated floating-point
arithmetic instructions.
In contrast, arithmetic results produced on Intel Pentium 4/Xeon, AMD Opteron/Athlon64 or Intel EM64T
processors will usually closely match or be identical to those produced on a traditional RISC/UNIX system if
all scalar arithmetic is performed using SSE/SSE2 instructions. You should keep this in mind when portingChapter 3. Using Optimization & Parallelization
27
applications to and from systems which support both x87 and full SSE/SSE2 floating-point arithmetic. Many
subtle issues can arise which affect your numerical results, sometimes to several digits of accuracy.
Loop Unrolling using –Munroll
This optimization unrolls loops, executing multiple instances of the loop during each iteration. This reduces
branch overhead, and can improve execution speed by creating better opportunities for instruction scheduling.
A loop with a constant count may be completely unrolled or partially unrolled. A loop with a non-constant
count may also be unrolled. A candidate loop must be an innermost loop containing one to four blocks of
code. The following shows the use of the –Munroll option:
$ pgf95 -Munroll prog.f
The –Munroll option is included as part of –fast on all x86 and x64 targets. The loop unroller expands the
contents of a loop and reduces the number of times a loop is executed. Branching overhead is reduced when
a loop is unrolled two or more times, since each iteration of the unrolled loop corresponds to two or more
iterations of the original loop; the number of branch instructions executed is proportionately reduced. When a
loop is unrolled completely, the loop’s branch overhead is eliminated altogether.
Loop unrolling may be beneficial for the instruction scheduler. When a loop is completely unrolled or unrolled
two or more times, opportunities for improved scheduling may be presented. The code generator can take
advantage of more possibilities for instruction grouping or filling instruction delays found within the loop.
Example 3.1 and Example 3.2 show the effect of code unrolling on a segment that computes a dot product.
Example 3.1. Dot Product Code
REAL*4 A(100), B(100), Z
INTEGER I
DO I=1, 100
Z = Z + A(i) * B(i)
END DO
END
Example 3.2. Unrolled Dot Product Code
REAL*4 A(100), B(100), Z
INTEGER I
DO I=1, 100, 2
Z = Z + A(i) * B(i)
Z = Z + A(i+1) * B(i+1)
END DO
END
Using the –Minfo option, the compiler informs you when a loop is being unrolled. For example, a message
indicating the line number, and the number of times the code is unrolled, similar to the following will display
when a loop is unrolled:
dot:
5, Loop unrolled 5 times
Using the c: and n: sub-options to –Munroll, or using –Mnounroll, you can control whether
and how loops are unrolled on a file-by-file basis. Using directives or pragmas as specified in Chapter 6,PGI® User’s Guide
28
“Using Directives and Pragmas”, you can precisely control whether and how a given loop is unrolled. Refer
to Chapter 2, “Using Command Line Options”, for a detailed description of the –Munroll option.
Vectorization using –Mvect
The –Mvect option is included as part of –fast on all x86 and x64 targets. If your program contains
computationally-intensive loops, the –Mvect option may be helpful. If in addition you specify –Minfo,
and your code contains loops that can be vectorized, the compiler reports relevant information on the
optimizations applied.
When a PGI compiler command is invoked with the –Mvect option, the vectorizer scans code searching for
loops that are candidates for high-level transformations such as loop distribution, loop interchange, cache
tiling, and idiom recognition (replacement of a recognizable code sequence, such as a reduction loop, with
optimized code sequences or function calls). When the vectorizer finds vectorization opportunities, it internally
rearranges or replaces sections of loops (the vectorizer changes the code generated; your source code’s loops
are not altered). In addition to performing these loop transformations, the vectorizer produces extensive data
dependence information for use by other phases of compilation and detects opportunities to use vector or
packed Streaming SIMD Extensions (SSE) instructions on processors where these are supported.
The –Mvect option can speed up code which contains well-behaved countable loops which operate on large
REAL, REAL*4, REAL*8, INTEGER*4, COMPLEX or COMPLEX DOUBLE arrays in Fortran and their C/C++
counterparts. However, it is possible that some codes will show a decrease in performance when compiled
with –Mvect due to the generation of conditionally executed code segments, inability to determine data
alignment, and other code generation factors. For this reason, it is recommended that you check carefully
whether particular program units or loops show improved performance when compiled with this option
enabled.
Vectorization Sub-options
The vectorizer performs high-level loop transformations on countable loops. A loop is countable if the
number of iterations is set only before loop execution and cannot be modified during loop execution. Some
of the vectorizer transformations can be controlled by arguments to the –Mvect command line option. The
following sections describe the arguments that affect the operation of the vectorizer. In addition, some of these
vectorizer operations can be controlled from within code using directives and pragmas. For details on the use
of directives and pragmas, refer to Chapter 6, “Using Directives and Pragmas,” on page 63.
The vectorizer performs the following operations:
• Loop interchange
• Loop splitting
• Loop fusion
• Memory-hierarchy (cache tiling) optimizations
• Generation of SSE instructions on processors where these are supported
• Generation of prefetch instructions on processors where these are supported
• Loop iteration peeling to maximize vector alignmentChapter 3. Using Optimization & Parallelization
29
• Alternate code generation
By default, –Mvect without any sub-options is equivalent to:
-Mvect=assoc,cachesize=c
where c is the actual cache size of the machine.
This enables the options for nested loop transformation and various other vectorizer options. These defaults
may vary depending on the target system.
Assoc Option
The option –Mvect=assoc instructs the vectorizer to perform associativity conversions that can change
the results of a computation due to a round-off error (–Mvect=noassoc disables this option). For
example, a typical optimization is to change one arithmetic operation to another arithmetic operation that
is mathematically correct, but can be computationally different and generate faster code. This option is
provided to enable or disable this transformation, since a round-off error for such associativity conversions
may produce unacceptable results.
Cachesize Option
The option –Mvect=cachesize:n instructs the vectorizer to tile nested loop operations assuming a data
cache size of n bytes. By default, the vectorizer attempts to tile nested loop operations, such as matrix multiply,
using multi-dimensional strip-mining techniques to maximize re-use of items in the data cache.
SSE Option
The option –Mvect=sse instructs the vectorizer to automatically generate packed SSE (Streaming SIMD
Extensions), SSE2, and prefetch instructions when vectorizable loops are encountered. SSE instructions, first
introduced on Pentium III and AthlonXP processors, operate on single-precision floating-point data, and
hence apply only to vectorizable loops that operate on single-precision floating-point data. SSE2 instructions,
first introduced on Pentium 4, Xeon and Opteron processors, operate on double-precision floating-point
data. Prefetch instructions, first introduced on Pentium III and AthlonXP processors, can be used to improve
the performance of vectorizable loops that operate on either 32-bit or 64-bit floating-point data. Refer to
Table 2, “Processor Options,” on page xxvi for a concise list of processors that support SSE, SSE2 and prefetch
instructions.
Note
Program units compiled with –Mvect=sse will not execute on Pentium, Pentium Pro, Pentium II or
first generation AMD Athlon processors. They will only execute correctly on Pentium III, Pentium 4,
Xeon, EM64T, AthlonXP, Athlon64 and Opteron systems running an SSE-enabled operating system.
Prefetch Option
The option –Mvect=prefetch instructs the vectorizer to automatically generate prefetch instructions when
vectorizable loops are encountered, even in cases where SSE or SSE2 instructions are not generated. Usually,
explicit prefetching is not necessary on Pentium 4, Xeon and Opteron because these processors supportPGI® User’s Guide
30
hardware prefetching; nonetheless, it sometimes can be worthwhile to experiment with explicit prefetching.
Prefetching can be controlled on a loop-by-loop level using prefetch directives, which are described in detail
in “Prefetch Directives ,” on page 69.
Note
Program units compiled with –Mvect=prefetch will not execute correctly on Pentium, Pentium
Pro, or Pentium II processors. They will execute correctly only on Pentium III, Pentium 4, Xeon,
EM64T, AthlonXP, Athlon64 or Opteron systems. In addition, the prefetchw instruction is only
supported on AthlonXP, Athlon64 or Opteron systems and can cause instruction faults on non-AMD
processors. For this reason, the PGI compilers do not generate prefetchw instructions by default on
any target.
In addition to these sub-options to –Mvect, several other sub-options are supported. Refer to the description
of -M[no]vect in Chapter 15, “Command-Line Options Reference” for a detailed description of all available
sub-options.
Vectorization Example Using SSE/SSE2 Instructions
One of the most important vectorization options is -Mvect=sse. When you use this option, the compiler
automatically generates SSE and SSE2 instructions, where possible, when targeting processors on which
these instructions are supported. This process can improve performance by up to a factor of two compared
with the equivalent scalar code. All of the PGI Fortran, C and C++ compilers support this capability. Table 2,
“Processor Options,” on page xxvi shows which x86 and x64 processors support these instructions.
Prior to release 7.0 -Mvect=sse was omitted from the compiler switch -fast but included in -fastsse.
Since release 7.0 -fast is synonymous with -fastsse and therefore includes -Mvect=sse.
In the program in Example 3.3, “Vector operation using SSE instructions”, the vectorizer recognizes the vector
operation in subroutine 'loop' when either the compiler switch -Mvect=sse or -fast is used. This example
shows the compilation, informational messages, and runtime results using the SSE instructions on an AMD
Opteron processor-based system, along with issues that affect SSE performance.
First note that the arrays in Example 3.3 are single-precision and that the vector operation is done using a
unit stride loop. Thus, this loop can potentially be vectorized using SSE instructions on any processor that
supports SSE or SSE2 instructions. SSE operations can be used to operate on pairs of single-precision floatingpoint numbers, and do not apply to double-precision floating-point numbers. SSE2 instructions can be used
to operate on quads of single-precision floating-point numbers or on pairs of double-precision floating-point
numbers.
Loops vectorized using SSE or SSE2 instructions operate much more efficiently when processing vectors that
are aligned to a cache-line boundary. You can cause unconstrained data objects of size 16 bytes or greater
to be cache-aligned by compiling with the –Mcache_align switch. An unconstrained data object is a data
object that is not a common block member and not a member of an aggregate data structure.
Note
For stack-based local variables to be properly aligned, the main program or function must be
compiled with –Mcache_align.Chapter 3. Using Optimization & Parallelization
31
The –Mcache_align switch has no effect on the alignment of Fortran allocatable or automatic arrays. If
you have arrays that are constrained, such as vectors that are members of Fortran common blocks, you must
specifically pad your data structures to ensure proper cache alignment; –Mcache_align causes only the
beginning address of each common block to be cache-aligned.
The following examples show the results of compiling the example code with and without –Mvect=sse.
Example 3.3. Vector operation using SSE instructions
program vector_op
parameter (N = 9999)
real*4 x(N), y(N), z(N), W(N)
do i = 1, n
y(i) = i
z(i) = 2*i
w(i) = 4*i
enddo
do j = 1, 200000
call loop(x,y,z,w,1.0e0,N)
enddo
print *, x(1),x(771),x(3618),x(6498),x(9999)
end
subroutine loop(a,b,c,d,s,n)
integer i, n
real*4 a(n), b(n), c(n), d(n),s
do i = 1, n
a(i) = b(i) + c(i) - s * d(i)
enddo
end
Assume the preceding program is compiled as follows, where -Mvect=nosse disables SSE vectorization:
% pgf95 -fast -Mvect=nosse -Minfo vadd.f
vector_op:
4, Loop unrolled 4 times
loop:
18, Loop unrolled 4 times
The following output shows a sample result if the generated executable is run and timed on a standalone AMD
Opteron 2.2 Ghz system:
% /bin/time vadd
-1.000000 -771.000 -3618.000 -6498.00
-9999.00
5.39user 0.00system 0:05.40elapsed 99%CP
Now, recompile with SSE vectorization enabled, and you see results similar to these:
% pgf95 -fast -Minfo vadd.f -o vadd
vector_op:
4, Unrolled inner loop 8 times
Loop unrolled 7 times (completely unrolled)
loop:
18, Generated 4 alternate loops for the inner loop
Generated vector sse code for inner loop
Generated 3 prefetch instructions for this loop
Notice the informational message for the loop at line 18.PGI® User’s Guide
32
• The first two lines of the message indicate that the loop has been vectorized, SSE instructions have been
generated, and four alternate versions of the loop have also been generated. The loop count and alignments
of the arrays determine which of these versions is executed.
• The last line of the informational message indicates that prefetch instructions have been generated for three
loads to minimize latency of data transfers from main memory.
Executing again, you should see results similar to the following:
% /bin/time vadd
-1.000000 -771.000 -3618.00 -6498.00
-9999.0
3.59user 0.00system 0:03.59elapsed 100%CPU
The result is a 50% speed-up over the equivalent scalar, that is, the non-SSE, version of the program.
Speed-up realized by a given loop or program can vary widely based on a number of factors:
• When the vectors of data are resident in the data cache, performance improvement using vector SSE or SSE2
instructions is most effective.
• If data is aligned properly, performance will be better in general than when using vector SSE operations on
unaligned data.
• If the compiler can guarantee that data is aligned properly, even more efficient sequences of SSE
instructions can be generated.
• The efficiency of loops that operate on single-precision data can be higher. SSE2 vector instructions can
operate on four single-precision elements concurrently, but only two double-precision elements.
Note
Compiling with –Mvect=sse can result in numerical differences from the executables generated
with less optimization. Certain vectorizable operations, for example dot products, are sensitive
to order of operations and the associative transformations necessary to enable vectorization (or
parallelization).
Auto-Parallelization using -Mconcur
With the -Mconcur option the compiler scans code searching for loops that are candidates for autoparallelization. -Mconcur must be used at both compile-time and link-time. When the parallelizer finds
opportunities for auto-parallelization, it parallelizes loops and you are informed of the line or loop being
parallelized if the -Minfo option is present on the compile line. See “–M Optimization Controls,” on
page 229, for a complete specification of -Mconcur.
A loop is considered parallelizable if doesn't contain any cross-iteration data dependencies. Cross-iteration
dependencies from reductions and expandable scalars are excluded from consideration, enabling more loops
to be parallelizable. In general, loops with calls are not parallelized due to unknown side effects. Also, loops
with low trip counts are not parallelized since the overhead in setting up and starting a parallel loop will likely
outweigh the potential benefits. In addition, the default is to not parallelize innermost loops, since these often
by definition are vectorizable using SSE instructions and it is seldom profitable to both vectorize and parallelizeChapter 3. Using Optimization & Parallelization
33
the same loop, especially on multi-core processors. Compiler switches and directives are available to let you
override most of these restrictions on auto-parallelization.
Auto-parallelization Sub-options
The parallelizer performs various operations that can be controlled by arguments to the –Mconcur command
line option. The following sections describe these arguments that affect the operation of the vectorizer. In
addition, these vectorizer operations can be controlled from within code using directives and pragmas. For
details on the use of directives and pragmas, refer to Chapter 6, “Using Directives and Pragmas”.
By default, –Mconcur without any sub-options is equivalent to:
-Mconcur=dist:block
This enables parallelization of loops with blocked iteration allocation across the available threads of execution.
These defaults may vary depending on the target system.
Altcode Option
The option –Mconcur=altcode instructs the parallelizer to generate alternate serial code for parallelized
loops. If altcode is specified without arguments, the parallelizer determines an appropriate cutoff length and
generates serial code to be executed whenever the loop count is less than or equal to that length. If altcode:n
is specified, the serial altcode is executed whenever the loop count is less than or equal to n. If noaltcode is
specified, no alternate serial code is generated.
Dist Option
The option –Mconcur=dist:{block|cyclic} option specifies whether to assign loop iterations to the
available threads in blocks or in a cyclic (round-robin) fashion. Block distribution is the default. If cyclic is
specified, iterations are allocated to processors cyclically. That is, processor 0 performs iterations 0, 3, 6, etc.;
processor 1 performs iterations 1, 4, 7, etc.; and processor 2 performs iterations 2, 5, 8, etc.
Cncall Option
The option –Mconcur=cncall specifies that it is safe to parallelize loops that contain subroutine or function
calls. By default, such loops are excluded from consideration for auto-parallelization. Also, no minimum loop
count threshold must be satisfied before parallelization will occur, and last values of scalars are assumed to be
safe.
The environment variable NCPUS is checked at runtime for a parallel program. If NCPUS is set to 1, a parallel
program runs serially, but will use the parallel routines generated during compilation. If NCPUS is set to
a value greater than 1, the specified number of processors will be used to execute the program. Setting
NCPUS to a value exceeding the number of physical processors can produce inefficient execution. Executing a
program on multiple processors in an environment where some of the processors are being time-shared with
another executing job can also result in inefficient execution.
As with the vectorizer, the -Mconcur option can speed up code if it contains well-behaved countable loops
and/or computationally intensive nested loops that operate on arrays. However, it is possible that some codes
will show a decrease in performance on multi-processor systems when compiled with -Mconcur due to
parallelization overheads, memory bandwidth limitations in the target system, false-sharing of cache lines, orPGI® User’s Guide
34
other architectural or code-generation factors. For this reason, it is recommended that you check carefully
whether particular program units or loops show improved performance when compiled using this option.
If the compiler is not able to successfully auto-parallelize your application, you should refer to Chapter 5,
“Using OpenMP”. It is possible that insertion of explicit parallelization directives or pragmas, and use of the
–mp compiler option might enable the application to run in parallel.
Loops That Fail to Parallelize
In spite of the sophisticated analysis and transformations performed by the compiler, programmers will often
note loops that are seemingly parallel, but are not parallelized. In this subsection, we look at some examples of
common situations where parallelization does not occur.
Innermost Loops
As noted earlier in this chapter, the PGI compilers will not parallelize innermost loops by default, because it is
usually not profitable. You can override this default using the command-line option –Mconcur=innermost.
Timing Loops
Often, loops will occur in programs that are similar to timing loops. The outer loop in the following example is
one such loop.
do j = 1, 2
do i = 1, n
a(i) = b(i) + c(i)
1 enddo
enddo
The outer loop above is not parallelized because the compiler detects a cross-iteration dependence in the
assignment to a(i). Suppose the outer loop were parallelized. Then both processors would simultaneously
attempt to make assignments into a(1:n). Now in general the values computed by each processor for
a(1:n) will differ, so that simultaneous assignment into a(1:n) will produce values different from
sequential execution of the loops.
In this example, values computed for a(1:n) don’t depend on j, so that simultaneous assignment by both
processors will not yield incorrect results. However, it is beyond the scope of the compilers’ dependence
analysis to determine that values computed in one iteration of a loop don’t differ from values computed in
another iteration. So the worst case is assumed, and different iterations of the outer loop are assumed to
compute different values for a(1:n). Is this assumption too pessimistic? If j doesn’t occur anywhere within
a loop, the loop exists only to cause some delay, most probably to improve timing resolution. It is not usually
valid to parallelize timing loops; to do so would distort the timing information for the inner loops.
Scalars
Quite often, scalars will inhibit parallelization of non-innermost loops. There are two separate cases that
present problems. In the first case, scalars appear to be expandable, but appear in non-innermost loops, as in
the following example.
do j = 1, n
x = b(j)
do i = 1, n
a(i,j) = x + c(i,j) Chapter 3. Using Optimization & Parallelization
35
enddo
enddo
There are a number of technical problems to be resolved in order to recognize expandable scalars in noninnermost loops. Until this generalization occurs, scalars like x in the preceding code segment inhibit
parallelization of loops in which they are assigned. In the following example, scalar k is not expandable, and it
is not an accumulator for a reduction.
k = 1
do i = 1, n
do j = 1, n
1 a(j,i) = b(k) * x
enddo
k = i
2 if (i .gt. n/2) k = n - (i - n/2)
enddo
If the outer loop is parallelized, conflicting values are stored into k by the various processors. The variable k
cannot be made local to each processor because the value of k must remain coherent among the processors.
It is possible the loop could be parallelized if all assignments to k are placed in critical sections. However, it
is not clear where critical sections should be introduced because in general the value for k could depend on
another scalar (or on k itself), and code to obtain the value of other scalars must reside in the same critical
section.
In the example above, the assignment to k within a conditional at label 2 prevents k from being recognized
as an induction variable. If the conditional statement at label 2 is removed, k would be an induction variable
whose value varies linearly with j, and the loop could be parallelized.
Scalar Last Values
During parallelization, scalars within loops often need to be privatized; that is, each execution thread has its
own independent copy of the scalar. Problems can arise if a privatized scalar is accessed outside the loop. For
example, consider the following loop:
for (i = 1; i 5.0 ) t = x[i];
}
v = t;
The value of t may not be computed on the last iteration of the loop. Normally, if a scalar is assigned within
a loop and used following the loop, the PGI compilers save the last value of the scalar. However, if the loop
is parallelized and the scalar is not assigned on every iteration, it may be difficult, without resorting to costly
critical sections, to determine on what iteration t is last assigned. Analysis allows the compiler to determine
that a scalar is assigned on each iteration and hence that the loop is safe to parallelize if the scalar is used
later, as illustrated in the following example.
for ( i = 1; i < n; i++) {
if ( x[i] > 0.0 ) {
t = 2.0;
}
else {
t = 3.0;
y[i] = ...t;
}
}
v = t;PGI® User’s Guide
36
where t is assigned on every iteration of the loop. However, there are cases where a scalar may be
privatizable, but if it is used after the loop, it is unsafe to parallelize. Examine the following loop in which each
use of t within the loop is reached by a definition from the same iteration.
for ( i = 1; i < N; i++ ){
if( x[i] > 0.0 ){
t = x[i];
...
...
y[i] = ...t;
}
}
v = t;
Here t is privatizable, but the use of t outside the loop may yield incorrect results, since the compiler may
not be able to detect on which iteration of the parallelized loop t is last assigned. The compiler detects
the previous cases. When a scalar is used after the loop but is not defined on every iteration of the loop,
parallelization does not occur.
When the programmer knows that the scalar is assigned on the last iteration of the loop, the programmer
may use a directive or pragma to let the compiler know the loop is safe to parallelize. The Fortran directive
safe_lastval informs the compiler that, for a given loop, all scalars are assigned in the last iteration of the
loop; thus, it is safe to parallelize the loop. We could add the following line to any of our previous examples.
cpgi$l safe_lastval
The resulting code looks similar to this:
cpgi$l safe_lastval
...
for (i = 1; i 5.0 ) t = x[i];
}
v = t;
In addition, a command-line option –Msafe_lastval, provides this information for all loops within the routines
being compiled, which essentially provides global scope.
Processor-Specific Optimization and the Unified Binary
Different processors have differences, some subtle, in hardware features such as instruction sets and cache
size. The compilers make architecture-specific decisions about things such as instruction selection, instruction
scheduling, and vectorization. By default, the PGI compilers produce code specifically targeted to the type
of processor on which the compilation is performed. That is, the default is to use all supported instructions
wherever possible when compiling on a given system. As a result, executables created on a given system may
not be usable on previous generation systems. For example, executables created on a Pentium 4 may fail to
execute on a Pentium III or Pentium II.
All PGI compilers have the capability of generating unified binaries, which provide a low-overhead means for
generating a single executable that is compatible with and has good performance on more than one hardware
platform.
You can use the –tp option to control compilation behavior by specifying the processor or processors with
which the generated code is compatible. The compilers generate and combine into one executable multipleChapter 3. Using Optimization & Parallelization
37
binary code streams, each optimized for a specific platform. At runtime, the one executable senses the
environment and dynamically selects the appropriate code stream. For specific information on the –tp option,
see –tp [,target...] .
Executable size is automatically controlled via unified binary culling. Only those functions and subroutines
where the target affects the generated code have unique binary images, resulting in a code-size savings of from
10% to 90% compared to generating full copies of code for each target.
Programs can use PGI Unified Binary even if all of the object files and libraries are not compiled as unified
binaries. Like any other object file, you can use PGI Unified Binary object files to create programs or libraries.
No special start up code is needed; support is linked in from the PGI libraries.
The -Mpfi option disables generation of PGI Unified Binary. Instead, the default target auto-detect rules for the
host are used to select the target processor.
Interprocedural Analysis and Optimization using –Mipa
The PGI Fortran, C and C++ compilers use interprocedural analysis (IPA) that results in minimal changes
to makefiles and the standard edit-build-run application development cycle. Other than adding –Mipa to
the command line, no other changes are required. For reference and background, the process of building a
program without IPA is described below, followed by the minor modifications required to use IPA with the PGI
compilers. While the PGCC compiler is used here to show how IPA works, similar capabilities apply to each of
the PGI Fortran, C and C++ compilers.
Note
The examples use Linux file naming conventions. On Windows, ‘.o’ files would be ‘.obj’ files, and
‘a.out’ files would be ‘.exe’ files.
Building a Program Without IPA – Single Step
Using the pgcc command-level compiler driver, multiple source files can be compiled and linked into a single
executable with one command. The following example compiles and links three source files:
% pgcc -o a.out file1.c file2.c file3.c
In actuality, the pgcc driver executes several steps to produce the assembly code and object files
corresponding to each source file, and subsequently to link the object files together into a single executable
file. Thus, the command above is roughly equivalent to the following commands performed individually:
% pgcc -S -o file1.s file1.c
% as -o file1.o file1.s
% pgcc -S -o file2.s file2.c
% as -o file2.o file2.s
% pgcc -S -o file3.s file3.c
% as -o file3.o file3.s
% pgcc -o a.out file1.o file2.o file3.o
If any of the three source files is edited, the executable can be rebuilt with the same command line:
% pgcc -o a.out file1.c file2.c file3.c
This always works as intended, but has the side-effect of recompiling all of the source files, even if only one has
changed. For applications with a large number of source files, this can be time-consuming and inefficient.PGI® User’s Guide
38
Building a Program Without IPA - Several Steps
It is also possible to use individual pgcc commands to compile each source file into a corresponding object
file, and one to link the resulting object files into an executable:
% pgcc -c file1.c
% pgcc -c file2.c
% pgcc -c file3.c
% pgcc -o a.out file1.o file2.o file3.o
The pgcc driver invokes the compiler and assembler as required to process each source file, and invokes
the linker for the final link command. If you modify one of the source files, the executable can be rebuilt by
compiling just that file and then relinking:
% pgcc -c file1.c
% pgcc -o a.out file1.o file2.o file3.o
Building a Program Without IPA Using Make
The program compilation and linking process can be simplified greatly using the make utility on systems
where it is supported. Suppose you create a makefile containing the following lines:
a.out: file1.o file2.o file3.o
pgcc $(OPT) -o a.out file1.o file2.o file3.o
file1.o: file1.c
pgcc $(OPT) -c file1.c
file2.o: file2.c
pgcc $(OPT) -c file2.c
file3.o: file3.c
pgcc $(OPT) -c file3.c
It is then possible to type a single make command:
% make
The make utility determines which object files are out of date with respect to their corresponding source files,
and invokes the compiler to recompile only those source files and to relink the executable. If you subsequently
edit one or more source files, the executable can be rebuilt with the minimum number of recompilations using
the same single make command.
Building a Program with IPA
Interprocedural analysis and optimization (IPA) by the PGI compilers alters the standard and make utility
command-level interfaces as little as possible. IPA occurs in three phases:
• Collection: Create a summary of each function or procedure, collecting the useful information for
interprocedural optimizations. This is done during the compile step if the –Mipa switch is present on the
command line; summary information is collected and stored in the object file.
• Propagation: Process all the object files to propagate the interprocedural summary information across
function and file boundaries. This is done during the link step, when all the object files are combined, if the
–Mipa switch is present on the link command line.
• Recompile/Optimization: Recompile each of the object files with the propagated interprocedural
information, producing a specialized object file. This process is also done during the link step when the
–Mipa switch is present on the link command line.Chapter 3. Using Optimization & Parallelization
39
When linking with –Mipa, the PGI compilers automatically regenerate IPA-optimized versions of each object
file, essentially recompiling each file. If there are IPA-optimized objects from a previous build, the compilers
will minimize the recompile time by reusing those objects if they are still valid. They will still be valid if the IPAoptimized object is newer than the original object file, and the propagated IPA information for that file has not
changed since it was optimized.
After each object file has been recompiled, the regular linker is invoked to build the application with the IPAoptimized object files. The IPA-optimized object files are saved in the same directory as the original object
files, for use in subsequent program builds.
Building a Program with IPA - Single Step
By adding the –Mipa command line switch, several source files can be compiled and linked with
interprocedural optimizations with one command:
% pgcc -Mipa=fast -o a.out file1.c file2.c file3.c
Just like compiling without –Mipa, the driver executes several steps to produce the assembly and object files
to create the executable:
% pgcc -Mipa=fast -S -o file1.s file1.c
% as -o file1.o file1.s
% pgcc -Mipa=fast -S -o file2.s file2.c
% as -o file2.o file2.s
% pgcc -Mipa=fast -S -o file3.s file3.c
% as -o file3.o file3.s
% pgcc -Mipa=fast -o a.out file1.o file2.o file3.o
In the last step, an IPA linker is invoked to read all the IPA summary information and perform the
interprocedural propagation. The IPA linker reinvokes the compiler on each of the object files to recompile
them with interprocedural information. This creates three new objects with mangled names:
file1_ipa5_a.out.oo.o, file2_ipa5_a.out.oo.o, file2_ipa5_a.out.oo.o
The system linker is then invoked to link these IPA-optimized objects into the final executable. Later, if one of
the three source files is edited, the executable can be rebuilt with the same command line:
% pgcc -Mipa=fast -o a.out file1.c file2.c file3.c
This will work, but again has the side-effect of compiling each source file, and recompiling each object file at
link time.
Building a Program with IPA - Several Steps
Just by adding the –Mipa command-line switch, it is possible to use individual pgcc commands to compile
each source file, followed by a command to link the resulting object files into an executable:
% pgcc -Mipa=fast -c file1.c
% pgcc -Mipa=fast -c file2.c
% pgcc -Mipa=fast -c file3.c
% pgcc -Mipa=fast -o a.out file1.o file2.o file3.o
The pgcc driver invokes the compiler and assembler as required to process each source file, and invokes the
IPA linker for the final link command. If you modify one of the source files, the executable can be rebuilt by
compiling just that file and then relinking:
% pgcc -Mipa=fast -c file1.cPGI® User’s Guide
40
% pgcc -Mipa=fast -o a.out file1.o file2.o file3.o
When the IPA linker is invoked, it will determine that the IPA-optimized object for file1.o
(file1_ipa5_a.out.oo.o) is stale, since it is older than the object file1.o, and hence will need to be
rebuilt, and will reinvoke the compiler to generate it. In addition, depending on the nature of the changes
to the source file file1.c, the interprocedural optimizations previously performed for file2 and file3 may now
be inaccurate. For instance, IPA may have propagated a constant argument value in a call from a function
in file1.c to a function in file2.c; if the value of the argument has changed, any optimizations based on that
constant value are invalid. The IPA linker will determine which, if any, of any previously created IPA-optimized
objects need to be regenerated, and will reinvoke the compiler as appropriate to regenerate them. Only those
objects that are stale or which have new or different IPA information will be regenerated, which saves on
compile time.
Building a Program with IPA Using Make
As in the previous two sections, programs can be built with IPA using the make utility, just by adding the
–Mipa command-line switch:
OPT=-Mipa=fast a.out: file1.o file2.o file3.o
pgcc $(OPT) -o a.out file1.o file2.o file3.o
file1.o: file1.c
pgcc $(OPT) -c file1.c
file2.o: file2.c
pgcc $(OPT) -c file2.c
file3.o: file3.c
pgcc $(OPT) -c file3.c
Using the single make command invokes the compiler to generate any object files that are out-of-date, then
invoke pgcc to link the objects into the executable; at link time, pgcc calls the IPA linker to regenerate any
stale or invalid IPA-optimized objects.
% make
Questions about IPA
1. Why is the object file so large?
An object file created with –Mipa contains several additional sections. One is the summary information
used to drive the interprocedural analysis. In addition, the object file contains the compiler internal
representation of the source file, so the file can be recompiled at link time with interprocedural
optimizations. There may be additional information when inlining is enabled. The total size of the object
file may be 5-10 times its original size. The extra sections are not added to the final executable.
2. What if I compile with –Mipa and link without –Mipa?
The PGI compilers generate a legal object file, even when the source file is compiled with –Mipa. If
you compile with –Mipa and link without –Mipa, the linker is invoked on the original object files. A
legal executable will be generated; while this will not have the benefit of interprocedural optimizations,
any other optimizations will apply.
3. What if I compile without –Mipa and link with –Mipa?
At link time, the IPA linker must have summary information about all the functions or routines used
in the program. This information is created only when a file is compiled with –Mipa. If you compileChapter 3. Using Optimization & Parallelization
41
a file without –Mipa and then try to get interprocedural optimizations by linking with –Mipa, the IPA
linker will issue a message that some routines have no IPA summary information, and will proceed to
run the system linker using the original object files. If some files were compiled with –Mipa and others
were not, it will determine the safest approximation of the IPA summary information for those files not
compiled with –Mipa, and use that to recompile the other files using interprocedural optimizations.
4. Can I build multiple applications in the same directory with –Mipa?
Yes. Suppose you have three source files: main1.c, main2.c, and sub.c, where sub.c is shared
between the two applications. Suppose you build the first application with –Mipa, using this command:
% pgcc -Mipa=fast -o app1 main1.c sub.c
The the IPA linker creates two IPA-optimized object files:
main1_ipa4_app1.o sub_ipa4_app1.oo
It uses them to build the first application. Now suppose you build the second application using this
command:
% pgcc -Mipa=fast -o app2 main2.c sub.c
The IPA linker creates two more IPA-optimized object files:
main2_ipa4_app2.oo sub_ipa4_app2.oo
Note
There are now three object files for sub.c: the original sub.o, and two IPA-optimized
objects, one for each application in which it appears.
Note
5. How is the mangled name for the IPA-optimized object files generated?
The mangled name has '_ipa' appended, followed by the decimal number of the length of the
executable file name, followed by an underscore and the executable file name itself. The suffix is
changed to .oo (on Linux) or .oobj (on Windows) so linking *.o or *.obj does not pull in the IPAoptimized objects. If the IPA linker determines that the file would not benefit from any interprocedural
optimizations, it does not have to recompile the file at link time and uses the original object.
Profile-Feedback Optimization using –Mpfi/–Mpfo
The PGI compilers support many common profile-feedback optimizations, including semi-invariant value
optimizations and block placement. These are performed under control of the –Mpfi/–Mpfo command-line
options.
When invoked with the –Mpfi option, the PGI compilers instrument the generated executable for collection
of profile and data feedback information. This information can be used in subsequent compilations that
include the –Mpfo optimization option. –Mpfi must be used at both compile-time and link-time. Programs
compiled with –Mpfi include extra code to collect run-time statistics and write them out to a trace file. When
the resulting program is executed, a profile feedback trace file pgfi.out is generated in the current working
directory.PGI® User’s Guide
42
Note
Programs compiled and linked with –Mpfi execute more slowly due to the instrumentation and data
collection overhead. You should use executables compiled with –Mpfi only for execution of training
runs.
When invoked with the –Mpfo option, the PGI compilers use data from a pgfi.out profile feedback
tracefile to enable or enhance certain performance optimizations. Use of this option requires the presence of a
pgfi.out trace file in the current working directory.
Default Optimization Levels
The following table shows the interaction between the –O ,–g, and –M options. In the table,
level can be 0, 1, 2, 3 or 4, and can be vect, concur, unroll or ipa. The default optimization level is
dependent upon these command-line options.
Table 3.1. Optimization and –O, –g and –M Options
Optimize Option Debug Option –M Option Optimization Level
none none none 1
none none –M 2
none –g none 0
–O none or –g none 2
–Olevel none or –g none level
–Olevel <= 2 none or –g –M 2
Code that is not optimized yet compiled using the option –O0 can be significantly slower than code generated
at other optimization levels. The –M option, where is vect, concur, unroll or ipa, sets the
optimization level to 2 if no –O options are supplied. The –fast and –fastsse options set the optimization
level to a target-dependent optimization level if no –O options are supplied.
Local Optimization Using Directives and Pragmas
Command-line options let you specify optimizations for an entire source file. Directives supplied within a
Fortran source file and pragmas supplied within a C or C++ source file provide information to the compiler
and alter the effects of certain command-line options or the default behavior of the compiler. (Many directives
have a corresponding command-line option).
While a command line option affects the entire source file that is being compiled, directives and pragmas let
you do the following:
• Apply, or disable, the effects of a particular command-line option to selected subprograms or to selected
loops in the source file (for example, an optimization).
• Globally override command-line options.
• Tune selected routines or loops based on your knowledge or on information obtained through profiling.Chapter 3. Using Optimization & Parallelization
43
Chapter 6, “Using Directives and Pragmas” provides details on how to add directives and pragmas to your
source files.
Execution Timing and Instruction Counting
As this chapter shows, once you have a program that compiles, executes and gives correct results, you may
optimize your code for execution efficiency. Selecting the correct optimization level requires some thought
and may require that you compare several optimization levels before arriving at the best solution. To compare
optimization levels, you need to measure the execution time for your program. There are several approaches
you can take for timing execution. You can use shell commands that provide execution time statistics, you can
include function calls in your code that provide timing information, or you can profile sections of code. Timing
functions available with the PGI compilers include 3F timing routines, the SECNDS pre-declared function
in PGF77 or PGF95, or the SYSTEM_CLOCK or CPU_CLOCK intrinsics in PGF95 or PGHPF. In general, when
timing a program, you should try to eliminate or reduce the amount of system level activities such as program
loading, I/O and task switching.
The following example shows a fragment that indicates how to use SYSTEM_CLOCK effectively within an F90/
F95 or HPF program unit.
Example 3.4. Using SYSTEM_CLOCK code fragment
. . .
integer :: nprocs, hz, clock0, clock1
real :: time
integer, allocatable :: t(:)
!hpf$ distribute t(cyclic)
#if defined (HPF)
allocate (t(number_of_processors()))
#elif defined (_OPENMP)
allocate (t(OMP_GET_NUM_THREADS()))
#else
allocate (t(1))
#endif
call system_clock (count_rate=hz)
!
call system_clock(count=clock0)
< do work>
call system_clock(count=clock1)
!
t = (clock1 - clock0)
time = real (sum(t)) / (real(hz) * size(t))
. . .
Portability of Multi-Threaded Programs on Linux
PGI has created two libraries - libpgbind and libnuma - to handle the variations between various
implementations of Linux.
Some older versions of Linux are lacking certain features that support multi-processor and multi-core systems,
in particular, the system call 'sched_setaffinity' and the numa library libnuma. The PGI run-time library uses
these features to implement some –Mconcur and –mp operations.
These variations have led to the creation of two PGI libraries, libpgbind and libnuma. These libraries are used
on all 32-bit and 64-bit Linux systems. These libraries are not needed on Windows.PGI® User’s Guide
44
When a program is linked with the system libnuma library, the program depends on the libnuma library in
order to run. On systems without a system libnuma library, the PGI version of libnuma provides the required
stubs so that the program links and executes properly.
If the program is linked with libpgbind and libnuma, the differences between systems is masked by the
different versions of libpgbind and libnuma. In particular, PGI provides two versions of libpgbind - one for
systems with working support for sched_setaffinity and another for systems that do not.
When a program is deployed to the target system, the proper set of libraries, real or stub, should be deployed
with the program.
This facility requires that the program be dynamically linked with libpgbind and libnuma.
libpgbind
On some versions of Linux, the system call sched_setaffinity does not exist or does not work. The library
libpgbind is used to work around this problem.
During installation, a small test program is compiled, linked, and executed. If the test program compiles, links,
and executes successfully, the installed version of libpgbind calls the system sched_setaffinity, otherwise the
stub version is installed.
libnuma
Not all systems have libnuma. Typically, only numa systems will have this library. PGI supplies a stub version of
libnuma which satisfies the calls from the PGI runtime to libnuma. Note that libnuma is a shared library that is
linked dynamically at runtime.
The reason to have a numa library on all systems is to allow multi-threaded programs (e.g. compiled with
–Mconcur or –mp ) to be compiled, linked, and executed without regard to whether the host or target
systems has a numa library. When the numa library is not available, a multi-threaded program still runs
because the calls to the numa library are satisfied by the PGI stub library.
During installation, the installation procedure checks for the existence of a real libnuma among the system
libraries. If the real library is not found, the PGI stub version is substituted.45
Chapter 4. Using Function Inlining
Function inlining replaces a call to a function or a subroutine with the body of the function or subroutine. This
can speed up execution by eliminating parameter passing and function/subroutine call and return overhead.
It also allows the compiler to optimize the function with the rest of the code. Note that using function inlining
indiscriminately can result in much larger code size and no increase in execution speed.
The PGI compilers provide two categories of inlining:
• Automatic inlining - During the compilation process, a hidden pass precedes the compilation pass.
This hidden pass extracts functions that are candidates for inlining. The inlining of functions occurs as the
source files are compiled.
• Inline libraries - You create inline libraries, for example using the pgf95 compiler driver and the
–Mextract and –o options. There is no hidden extract pass but you must ensure that any files that depend
on the inline library use the latest version of the inline library.
There are important restrictions on inlining. Inlining only applies to certain types of functions. Refer to
“Restrictions on Inlining,” on page 49 for more details on function inlining limitations.
This chapter describes how to use the following options related to function inlining:
–Mextract
–Minline
–Mrecursive
Invoking Function Inlining
To invoke the function inliner, use the -Minline option. If you do not specify an inline library, the compiler
performs a special prepass on all source files named on the compiler command line before it compiles any of
them. This pass extracts functions that meet the requirements for inlining and puts them in a temporary inline
library for use by the compilation pass.
Several -Minline suboptions let you determine the selection criteria for functions to be inlined. These
suboptions include:PGI® User’s Guide
46
except:func
Inlines all eligible functions except func, a function in the source text. You can us a comma-separated list
to specify multiple functions.
[name:]func
Inlines all functions in the source text whose name matches func. You can us a comma-separated list to
specify multiple functions.
[size:]n
Inlines functions with a statement count less than or equal to n, the specified size.
Note
The size n may not exactly equal the number of statements in a selected function; the size
parameter is merely a rough gauge.
levels:n
Inlines n level of function calling levels. The default number is one (1). Using a level greater than one
indicates that function calls within inlined functions may be replaced with inlined code. This approach
allows the function inliner to automatically perform a sequence of inline and extract processes.
[lib:]file.ext
Instructs the inliner to inline the functions within the library file file.ext. If no inline library is
specified, functions are extracted from a temporary library created during an extract prepass.
Tip
Create the library file using the -Mextract option.
If you specify both a function name and a size n, the compiler inlines functions that match the function name
or have n or fewer statements.
If a name is used without a keyword, then a name with a period is assumed to be an inline library and a name
without a period is assumed to be a function name. If a number is used without a keyword, the number is
assumed to be a size.
In the following example, the compiler inlines functions with fewer than approximately 100 statements in the
source file myprog.f and writes the executable code in the default output file a.out.
$ pgf95 -Minline=size:100 myprog.f
Refer to “–M Options by Category,” on page 219 for more information on the -Minline options.
Using an Inline Library
If you specify one or more inline libraries on the command line with the -Minline option, the compiler does
not perform an initial extract pass. The compiler selects functions to inline from the specified inline library.
If you also specify a size or function name, all functions in the inline library meeting the selection criteria are
selected for inline expansion at points in the source text where they are called.
If you do not specify a function name or a size limitation for the -Minline option, the compiler inlines every
function in the inline library that matches a function in the source text.Chapter 4. Using Function Inlining
47
In the following example, the compiler inlines the function proc from the inline library lib.il and writes
the executable code in the default output file a.out.
$ pgf95 -Minline=name:proc,lib:lib.il myprog.f
The following command line is equivalent to the preceding line, with the exception that in the following
example does not use the keywords name: and lib:. You typically use keywords to avoid name conflicts
when you use an inline library name that does not contain a period. Otherwise, without the keywords, a period
informs the compiler that the file on the command line is an inline library.
$ pgf95 -Minline=proc,lib.il myprog.f
Creating an Inline Library
You can create or update an inline library using the -Mextract command-line option. If you do not specify
selection criteria with the -Mextract option, the compiler attempts to extract all subprograms.
Several -Mextract options let you determine the selection criteria for creating or updating an inline library.
These selection criteria include:
func
Extracts the function func. You can us a comma-separated list to specify multiple functions.
[name:]func
Extracts the functions whose name matches func, a function in the source text.
[size:]n
Limits the size of the extracted functions to functions with a statement count less than or equal to n, the
specified size.
Note
The size n may not exactly equal the number of statements in a selected function; the size
parameter is merely a rough gauge.
[lib:]ext.lib
Stores the extracted information in the library directory ext.lib.
If no inline library is specified, functions are extracted to a temporary library created during an extract
prepass for use during the compilation stage.
When you use the -Mextract option, only the extract phase is performed; the compile and link phases
are not performed. The output of an extract pass is a library of functions available for inlining. This output is
placed in the inline library file specified on the command line with the –o filename specification. If the library
file exists, new information is appended to it. If the file does not exist, it is created. You can use a command
similar to the following:
$ pgf95 -Mextract=lib:lib.il myfunc.f
You can use the -Minline option with the -Mextract option. In this case, the extracted library of functions
can have other functions inlined into the library. Using both options enables you to obtain more than one
level of inlining. In this situation, if you do not specify a library with the –Minline option, the inline processPGI® User’s Guide
48
consists of two extract passes. The first pass is a hidden pass implied by the –Minline option, during which
the compiler extracts functions and places them into a temporary library. The second pass uses the results of
the first pass but puts its results into the library that you specify with the –o option.
Working with Inline Libraries
An inline library is implemented as a directory with each inline function in the library stored as a file using an
encoded form of the inlinable function.
A special file named TOC in the inline library directory serves as a table of contents for the inline library.
This is a printable, ASCII file which can be examined to find out information about the library contents, such
as names and sizes of functions, the source file from which they were extracted, the version number of the
extractor which created the entry, etc.
Libraries and their elements can be manipulated using ordinary system commands.
• Inline libraries can be copied or renamed.
• Elements of libraries can be deleted or copied from one library to another.
• The ls or dir command can be used to determine the last-change date of a library entry.
Dependencies
When a library is created or updated using one of the PGI compilers, the last-change date of the library
directory is updated. This allows a library to be listed as a dependence in a makefile or a PVF property and
ensures that the necessary compilations are performed when a library is changed.
Updating Inline Libraries - Makefiles
If you use inline libraries you need to be certain that they remain up to date with the source files into which
they are inlined. One way to assure inline libraries are updated is to include them in a makefile. The makefile
fragment in the following example assumes the file utils.f contains a number of small functions used in
the files parser.f and alloc.f. The makefile also maintains the inline library utils.il. The makefile
updates the library whenever you change utils.f or one of the include files it uses. In turn, the makefile
compiles parser.f and alloc.f whenever you update the library.
Example 4.1. Sample Makefile
SRC = mydir
FC = pgf95
FFLAGS = -O2
main.o: $(SRC)/main.f $(SRC)/global.h
$(FC) $(FFLAGS) -c $(SRC)/main.f
utils.o: $(SRC)/utils.f $(SRC)/global.h $(SRC)/utils.h
$(FC) $(FFLAGS) -c $(SRC)/utils.f
utils.il: $(SRC)/utils.f $(SRC)/global.h $(SRC)/utils.h
$(FC) $(FFLAGS) -Mextract=15 -o utils.il utils.f
parser.o: $(SRC)/parser.f $(SRC)/global.h utils.il
$(FC) $(FFLAGS) -Minline=utils.il -c $(SRC)/parser.f
alloc.o: $(SRC)/alloc.f $(SRC)/global.h utils.il
$(FC) $(FFLAGS) -Minline=utils.il -c $(SRC)/alloc.f
myprog: main.o utils.o parser.o alloc.o
$(FC) -o myprog main.o utils.o parser.o alloc.oChapter 4. Using Function Inlining
49
Error Detection during Inlining
To request inlining information from the compiler when you invoke the inliner, specify the –Minfo=inline
option. For example:
$ pgf95 -Minline=mylib.il -Minfo=inline myext.f
Examples
Assume the program dhry consists of a single source file dhry.f. The following command line builds an
executable file for dhry in which proc7 is inlined wherever it is called:
$ pgf95 dhry.f -Minline=proc7
The following command lines build an executable file for dhry in which proc7 plus any functions of
approximately 10 or fewer statements are inlined (one level only).
Note
The specified functions are inlined only if they are previously placed in the inline library, temp.il,
during the extract phase.
$ pgf95 dhry.f -Mextract=lib:temp.il
$ pgf95 dhry.f -Minline=10,proc7,temp.il
Using the same source file dhry.f, the following example builds an executable for dhry in which all functions
of roughly ten or fewer statements are inlined. Two levels of inlining are performed. This means that if function
A calls function B, and B calls C, and both B and C are inlinable, then the version of B which is inlined into A
will have had C inlined into it.
$ pgf95 dhry.f -Minline=size:10,levels:2
Restrictions on Inlining
The following Fortran subprograms cannot be extracted:
• Main or BLOCK DATA programs.
• Subprograms containing alternate return, assigned GO TO, DATA, SAVE, or EQUIVALENCE statements.
• Subprograms containing FORMAT statements.
• Subprograms containing multiple entries.
A Fortran subprogram is not inlined if any of the following applies:
• It is referenced in a statement function.
• A common block mismatch exists; in other words, the caller must contain all common blocks specified
in the callee, and elements of the common blocks must agree in name, order, and type (except that the
caller's common block can have additional members appended to the end of the common block).
• An argument mismatch exists; in other words, the number and type (size) of actual and formal parameters
must be equal.PGI® User’s Guide
50
• A name clash exists, such as a call to subroutine xyz in the extracted subprogram and a variable named
xyz in the caller.
The following types of C and C++ functions cannot be inlined:
• Functions containing switch statements
• Functions which reference a static variable whose definition is nested within the function
• Function which accept a variable number of arguments
Certain C/C++ functions can only be inlined into the file that contains their definition:
• Static functions
• Functions which call a static function
• Functions which reference a static variable51
Chapter 5. Using OpenMP
The PGF77 and PGF95 Fortran compilers support the OpenMP Fortran Application Program Interface. The
PGCC ANSI C and C++ compilers support the OpenMP C/C++ Application Program Interface. The OpenMP
shared-memory parallel programming model is defined by a collection of compiler directives or pragmas,
library routines, and environment variables that can be used to specify shared-memory parallelism in Fortran,
C and C++ programs. The Fortran directives and C/C++ pragmas include a parallel region construct for
writing coarse grain SPMD programs, work-sharing constructs which specify that DO loop iterations or
C/C++ for loop iterations should be split among the available threads of execution, and synchronization
constructs. The data environment is controlled either by using clauses on the directives or pragmas, or
with additional directives or pragmas. Run-time library routines are provided to query the parallel runtime
environment, for example to determine how many threads are participating in execution of a parallel region.
Finally, environment variables are provided to control the execution behavior of parallel programs. For more
information on OpenMP, see www.openmp.org.
Fortran directives and C/C++ pragmas allow users to place hints in the source code to help the compiler
generate better assembly code. You typically use directives and pragmas to control the actions of the compiler
in a particular portion of a program without affecting the program as a whole. You place them in your source
code where you want them to take effect. Typically they stay in effect from the point where included until the
end of the compilation unit or until another directive or pragma changes its status.
Fortran Parallelization Directives
Parallelization directives are comments in a program that are interpreted by the PGI Fortran compilers when
the option –mp is specified on the command line. The form of a parallelization directive is:
sentinel directive_name [clauses]
With the exception of the SGI-compatible DOACROSS directive, the sentinel must comply with these rules:
• Be one of these: !$OMP, C$OMP, or *$OMP.
• Must start in column 1 (one).
• Must appear as a single word without embedded white space.
• The sentinel marking a DOACROSS directive is C$.PGI® User’s Guide
52
The directive_name can be any of the directives listed in Table 5.1, “Directive and Pragma Summary Table,”
on page 53. The valid clauses depend on the directive. Chapter 16, “OpenMP Reference Information”
provides a list of directives and their clauses, their usage, and examples.
In addition to the sentinel rules, the directive must also comply with these rules:
• Standard Fortran syntax restrictions, such as line length, case insensitivity, and so on, apply to the directive
line.
• Initial directive lines must have a space or zero in column six.
• Continuation directive lines must have a character other than a space or a zero in column six. Continuation
lines for C$DOACROSS directives are specified using the C$& sentinel.
• Directives which are presented in pairs must be used in pairs.
Clauses associated with directives have these characteristics:
• The order in which clauses appear in the parallelization directives is not significant.
• Commas separate clauses within the directives, but commas are not allowed between the directive name and
the first clause.
• Clauses on directives may be repeated as needed, subject to the restrictions listed in the description of each
clause.
C/C++ Parallelization Pragmas
Parallelization pragmas are #pragma statements in a C or C++ program that are interpreted by the PGCC C and
C++ compilers when the option -mp is specified on the command line. The form of a parallelization pragma
is:
#pragma omp pragma_name [clauses]
The format for pragmas include these standards:
• The pragmas follow the conventions of the C and C++ standards.
• Whitespace can appear before and after the #.
• Preprocessing tokens following the #pragma omp are subject to macro replacement.
• The order in which clauses appear in the parallelization pragmas is not significant.
• Spaces separate clauses within the pragmas.
• Clauses on pragmas may be repeated as needed subject to the restrictions listed in the description of each
clause.
For the purposes of the OpenMP pragmas, a C/C++ structured block is defined to be a statement or compound
statement (a sequence of statements beginning with { and ending with }) that has a single entry and a single
exit. No statement or compound statement is a C/C++ structured block if there is a jump into or out of that
statement.Chapter 5. Using OpenMP
53
Directive and Pragma Recognition
The compiler option –mp enables recognition of the parallelization directives and pragmas. The use of this
option also implies:
–Mreentrant
Local variables are placed on the stack and optimizations, such as -Mnoframe, that may result in nonreentrant code are disabled.
–Miomutex
For directives, critical sections are generated around Fortran I/O statements.
For pragmas, calls to I/O library functions are system-dependent and are not necessarily guaranteed to be
thread-safe. I/O library calls within parallel regions should be protected by critical regions, as shown in the
examples in Chapter 16, “OpenMP Reference Information”, to ensure they function correctly on all systems.
Directive and Pragma Summary Table
The following table provides a brief summary of the directives and pragmas that PGI supports. For complete
information on these statement and examples, refer to Chapter 16, “OpenMP Reference Information”.
Table 5.1. Directive and Pragma Summary Table
Fortran Directive and C/C++
Pragma
Description
“ATOMIC ,” on page 244
omp atomic
Semantically equivalent to enclosing a single statement
in the CRITCIAL...END CRITICAL directive or omp critical
pragma. Note: Only certain statements are allowed.
“BARRIER,” on page 244
omp barrier
Synchronizes all threads at a specific point in a program
so that all threads complete work to that point before any
thread continues.
“CRITICAL ... END CRITICAL and omp
critical ,” on page 245
Defines a subsection of code within a parallel region, a
critical section, which is executed one thread at a time.
“DO ... END DO and omp for ,” on
page 247
Provides a mechanism for distribution of loop iterations
across the available threads in a parallel region.
“C$DOACROSS ,” on page 246 Specifies that the compiler should parallelize the loop to
which it applies, even though that loop is not contained
within a parallel region.
“FLUSH and omp flush pragma ,” on
page 249
When this appears, all processor-visible data items, or,
when a list is present (FLUSH [list]), only those specified
in the list, are written to memory, thus ensuring that all the
threads in a team have a consistent view of certain objects
in memory.
“MASTER ... END MASTER and omp
master pragma ”
Designates code that executes on the master thread and that
is skipped by the other threads.PGI® User’s Guide
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Fortran Directive and C/C++
Pragma
Description
“ORDERED ,” on page 251
omp ordered
Defines a code block that is executed by only one thread at
a time, and in the order of the loop iterations; this makes
the ordered code block sequential, while allowing parallel
execution of statements outside the code block.
“PARALLEL DO ,” on page 254
omp parallel for
Enables you to specify which loops the compiler should
parallelize.
“PARALLEL ... END PARALLEL and
omp parallel ,” on page 251
Supports a fork/join execution model in which a single
thread executes all statements until a parallel region is
encountered.
“PARALLEL SECTIONS ,” on page
255
omp parallel sections
Defines a non-iterative work-sharing construct without the
need to define an enclosing parallel region.
“PARALLEL WORKSHARE ,” on page
256
Provides a short form method for including a WORKSHARE
directive inside a PARALLEL construct.
“SECTIONS … END SECTIONS ,” on
page 257
omp sections
Defines a non-iterative work-sharing construct within a
parallel region.
“SINGLE ... END SINGLE,” on page
257S
omp master
Designates code that executes on a single thread and that is
skipped by the other threads.
“THREADPRIVATE ,” on page 258
omp threadprivate
When a common block or variable that is initialized
appears in this directive or pragma, each thread’s copy is
initialized once prior to its first use.
“WORKSHARE ... END WORKSHARE,”
on page 259
omp for
Provides a mechanism to effect parallel execution of noniterative but implicitly data parallel constructs.
Directive and Pragma Clauses
Some directives and pragmas accept clauses that further allow a user to control the scope attributes of
variables for the duration of the directive or pragma. Not all clauses are allowed on all directives, so the
clauses that are valid are included with the description of the directive and pragma. Typically, if no data scope
clause is specified for variables, the default scope is share.
Table 16.2, “Directive and Pragma Clauses ,” on page 260 provides a brief summary of the clauses
associated with OPENMP directives and pragmas that PGI supports.Chapter 5. Using OpenMP
55
For complete information on these clauses, refer to the OpenMP documentation available on the WorldWide
Web.
Run-time Library Routines
User-callable functions are available to the Fortran and to the OpenMP C/C++ programmer to query and alter
the parallel execution environment.
Any C/C++ program unit that invokes these functions should include the statement #include .
The omp.h include file contains definitions for each of the C/C++ library routines and two required type
definitions. For example, to use the omp_get_num_threads function, use this syntax:
#include
int omp_get_num_threads(void);
The following table summarizes the run-time library calls.
Note
The Fortran call is shown first followed by the equivalent C++ call.
Table 5.2. Run-time Library Call Summary
Run-time Library Call with Examples
omp_get_num_threads
Returns the number of threads in the team executing the parallel region from which it is called. When
called from a serial region, this function returns 1. A nested parallel region is the same as a single
parallel region.
By default, the value returned by this function is equal to the value of the environment variable
OMP_NUM_THREADS or to the value set by the last previous call to omp_set_num_threads().
Fortran integer omp_get_num_threads()
C/C++ #include int omp_get_num_threads(void);
omp_set_num_threads
Sets the number of threads to use for the next parallel region.
This subroutine or function can only be called from a serial region of code. If it is called from
within a parallel region, or from within a subroutine or function that is called from within a parallel
region, the results are undefined. Further, this subroutine or function has precedence over the
OMP_NUM_THREADS environment variable.
Fortran subroutine omp_set_num_threads(scalar_integer_exp)
C/C++ #include void omp_set_num_threads(int num_threads);
omp_get_thread_num
Returns the thread number within the team. The thread number lies between 0 and
omp_get_num_threads()-1. When called from a serial region, this function returns 0. A nested
parallel region is the same as a single parallel region.
Fortran integer omp_get_thread_num()PGI® User’s Guide
56
Run-time Library Call with Examples
C/C++ #include int omp_get_thread_num(void);
omp_get_max_threads
Returns the maximum value that can be returned by calls to omp_get_num_threads().
If omp_set_num_threads() is used to change the number of processors, subsequent calls to
omp_get_max_threads() return the new value. Further, this function returns the maximum value
whether executing from a parallel or serial region of code.
Fortran integer function omp_get_max_threads()
C/C++ #include void omp_get_max_threads(void)
omp_get_num_procs
Returns the number of processors that are available to the program
Fortran integer function omp_get_num_procs()
C/C++ #include int omp_get_num_procs(void);
omp_get_stack_size
Returns the value of the OpenMP internal control variable that specifies the size that is used to create a
stack for a newly created thread.
This value may not be the size of the stack of the current thread.
Fortran !omp_get_stack_size interface
function omp_get_stack_size ()
use omp_lib_kinds
integer ( kind=OMP_STACK_SIZE_KIND )
:: omp_get_stack_size
end function omp_get_stack_size
end interface
C/C++ #include size_t omp_get_stack_size(void);
omp_set_stack_size
Changes the value of the OpenMP internal control variable that specifies the size to be used to create a
stack for a newly created thread.
The integer argument specifies the stack size in kilobytes. The size of the stack of the current thread
cannot be changed. In the PGI implementation, all OpenMP or auto-parallelization threads are created
just prior to the first parallel region; therefore, only calls to omp_set_stack_size() that occur
prior to the first region have an effect.
Fortran: subroutine omp_set_stack_size(integer(KIND=OMP_STACK_SIZE_KIND))
C/C++ #include void omp_set_stack_size(size_t);
omp_in_parallel
Returns whether or not the call is within a parallel region.
Returns .TRUE.for directives and non-zero for pragmas if called from within a parallel region and
.FALSE. for directives and zero for pragmas if called outside of a parallel region. When calledChapter 5. Using OpenMP
57
Run-time Library Call with Examples
from within a parallel region that is serialized, for example in the presence of an IF clause evaluating
.FALSE.for directives and zero for pragmas, the function returns .FALSE. for directives and zero
for pragmas.
Fortran logical function omp_in_parallel()
C/C++ #include int omp_in_parallel(void);
omp_set_dynamic
Allows automatic dynamic adjustment of the number of threads used for execution of parallel regions.
This function is recognized, but currently has no effect.
Fortran subroutine omp_set_dynamic(scalar_logical_exp)
C/C++ #include void omp_set_dynamic(int dynamic_threads);
omp_get_dynamic
Allows the user to query whether automatic dynamic adjustment of the number of threads used for
execution of parallel regions is enabled.
This function is recognized, but currently always returns .FALSE.for directives and zero for pragmas.
Fortran logical function omp_get_dynamic()
C/C++ #include void omp_get_dynamic(void);
omp_set_nested
Allows enabling/disabling of nested parallel regions.
This function is recognized, but currently has no effect.
Fortran subroutine omp_set_nested(scalar_logical_exp)
C/C++ #include void omp_set_nested(int nested);
omp_get_nested
Allows the user to query whether dynamic adjustment of the number of threads available for execution
of parallel regions is enabled.
This function is recognized, but currently always returns .FALSE. for directives and zero for pragmas.
Fortran logical function omp_get_nested()
C/C++ #include int omp_get_nested(void);
omp_get_wtime
Returns the elapsed wall clock time, in seconds, as a DOUBLE PRECISION value for directives and as a
floating-point double value for pragmas.
Times returned are per-thread times, and are not necessarily globally consistent across all threads.
Fortran double precision function omp_get_wtime()
C/C++ #include double omp_get_wtime()
omp_get_wtickPGI® User’s Guide
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Run-time Library Call with Examples
Returns the resolution of omp_get_wtime(), in seconds, as a DOUBLE PRECISION value for Fortran
directives and as a floating-point double value for C/C++ pragmas.
Fortran double precision function omp_get_wtick()
C/C++ #include double omp_get_wtick()
omp_init_lock
Initializes a lock associated with the variable lock for use in subsequent calls to lock routines.
The initial state of the lock is unlocked. If the variable is already associated with a lock, it is illegal to
make a call to this routine.
Fortran subroutine omp_init_lock(integer_var)
C/C++ #include void omp_init_lock(omp_lock_t *lock);
void omp_init_nest_lock(omp_nest_lock_t *lock);
omp_destroy_lock
Disassociates a lock associated with the variable.
Fortran subroutine omp_destroy_lock(integer_var)
C/C++ #include void omp_destroy_lock(omp_lock_t *lock);
void omp_destroy_nest_lock(omp_nest_lock_t *lock);
omp_set_lock
Causes the calling thread to wait until the specified lock is available.
The thread gains ownership of the lock when it is available. If the variable is not already associated with
a lock, it is illegal to make a call to this routine.
Fortran subroutine omp_set_lock(integer_var)
C/C++ #include void omp_set_lock(omp_lock_t *lock);
void omp_set_nest_lock(omp_nest_lock_t *lock);
omp_unset_lock
Causes the calling thread to release ownership of the lock associated with integer_var.
If the variable is not already associated with a lock, it is illegal to make a call to this routine.
Fortran subroutine omp_unset_lock(integer_var)
C/C++ #include void omp_unset_lock(omp_lock_t *lock);
void omp_unset_nest_lock(omp_nest_lock_t *lock);
omp_test_lock
Causes the calling thread to try to gain ownership of the lock associated with the variable.
The function returns .TRUE.for directives and non-zero for pragmas if the thread gains ownership
of the lock; otherwise it returns .FALSE. for directives and zero for pragmas. If the variable is not
already associated with a lock, it is illegal to make a call to this routine.
Fortran logical function omp_test_lock(integer_var)
C/C++ #include int omp_test_lock(omp_lock_t *lock);Chapter 5. Using OpenMP
59
Run-time Library Call with Examples
int omp_test_nest_lock(omp_nest_lock_t *lock);
Environment Variables
You can use OpenMP environment variables to control the behavior of OpenMP programs. These environment
variables allow you to set and pass information that can alter the behavior of directives and pragmas.
The following summary table is a quick reference for the OPENMP environment variables that PGI uses.
Detailed descriptions of each of these variables immediately follows the table.
Table 5.3. OpenMP-related Environment Variable Summary Table
Environment Variable Default Description
OMP_DYNAMIC FALSE Currently has no effect. Typically enables (TRUE) or
disables (FALSE) the dynamic adjustment of the number of
threads.
OMP_NESTED FALSE Currently has no effect. Typically enables (TRUE) or
disables (FALSE) nested parallelism.
OMP_NUM_THREADS 1 Specifies the number of threads to use during execution of
parallel regions.
OMP_SCHEDULE STATIC with
chunk size of 1
Specifies the type of iteration scheduling and optionally the
chunk size to use for omp for and omp parallel for loops
that include the run-time schedule clause.
OMP_STACK_SIZE Overrides the default stack size for a newly created thread.
OMP_WAIT_POLICY ACTIVE Sets the behavior of idle threads, defining whether they spin
or sleep when idle. The values are ACTIVE and PASSIVE.
OMP_DYNAMIC
OMP_DYNAMIC currently has no effect. Typically this variable enables (TRUE) or disables (FALSE) the
dynamic adjustment of the number of threads.
OMP_NESTED
OMP_NESTED currently has no effect. Typically this variable enables (TRUE) or disables (FALSE) nested
parallelism.
OMP_NUM_THREADS
OMP_NUM_THREADS specifies the number of threads to use during execution of parallel regions. The
default value for this variable is 1. For historical reasons, the environment variable NCPUS is supported with
the same functionality. In the event that both OMP_NUM_THREADS and NCPUS are defined, the value of
OMP_NUM_THREADS takes precedence.PGI® User’s Guide
60
NOTE
OMP_NUM_THREADS threads is used to execute the program regardless of the number of physical
processors available in the system. As a result, you can run programs using more threads than
physical processors and they execute correctly. However, performance of programs executed in this
manner can be unpredictable, and oftentimes will be inefficient.
OMP_SCHEDULE
OMP_SCHEDULE specifies the type of iteration scheduling to use for DO and PARALLEL DO loop directives and
for omp for and omp parallel for loop pragmas that include the SCHEDULE(RUNTIME) clause, described in
“Schedule Clause,” on page 261. The default value for this variable is STATIC
If the optional chunk size is not set, a chunk size of 1 is assumed except in the case of a static schedule. For a
static schedule, the default is as defined in “DO ... END DO and omp for ,” on page 247.
Examples of the use of OMP_SCHEDULE are as follows:
For Fortran:
$ setenv OMP_SCHEDULE "STATIC, 5"
$ setenv OMP_SCHEDULE "GUIDED, 8"
$ setenv OMP_SCHEDULE "DYNAMIC"
For C/C++:
$ setenv OMP_SCHEDULE "static, 5"
$ setenv OMP_SCHEDULE "guided, 8"
$ setenv OMP_SCHEDULE "dynamic"
OMP_STACK_SIZE
OMP_STACK_SIZE is an OpenMP 3.0 feature that controls the size of the stack for newly-created threads.
This variable overrides the default stack size for a newly created thread. The value is a decimal integer followed
by an optional letter B, K, M, or G, to specify bytes, kilobytes, megabytes, and gigabytes, respectively. If no letter
is used, the default is kilobytes. There is no space between the value and the letter; for example, one megabyte
is specified 1M. The following example specifies a stack size of 8 megabytes.
$ setenv OMP_STACK_SIZE 8M
The API functions related to OMP_STACK_SIZE are omp_set_stack_size and omp_get_stack_size.
The environment variable OMP_STACK_SIZE is read on program start-up. If the program changes its own
environment, the variable is not re-checked.
This environment variable takes precedence over MPSTKZ, described in “MPSTKZ,” on page 94. Once a
thread is created, its stack size cannot be changed.
In the PGI implementation, threads are created prior to the first parallel region and persist for the life
of the program. The stack size of the main program is set at program start-up and is not affected by
OMP_STACK_SIZE. For more information on controlling the program stack size in Linux, refer to “Running
Parallel Programs on Linux,” on page 9.
OMP_WAIT_POLICY
OMP_WAIT_POLICY sets the behavior of idle threads - specifically, whether they spin or sleep when idle. The
values are ACTIVE and PASSIVE, with ACTIVE the default. The behavior defined by OMP_WAIT_POLICY is also
shared by threads created by auto-parallelization.Chapter 5. Using OpenMP
61
• Threads are considered idle when waiting at a barrier, when waiting to enter a critical region, or when
unemployed between parallel regions.
• Threads waiting for critical sections always busy wait (ACTIVE).
• Barriers always busy wait (ACTIVE), with calls to sched_yield determined by the environment variable
MP_SPIN, described in “MP_SPIN,” on page 95.
• Unemployed threads during a serial region can either busy wait using the barrier (ACTIVE) or politely wait
using a mutex (PASSIVE). This choice is set by OMP_WAIT_POLICY, so the default is ACTIVE.
When ACTIVE is set, idle threads consume 100% of their CPU allotment spinning in a busy loop waiting to
restart in a parallel region. This mechanism allows for very quick entry into parallel regions, a condition which
is good for programs that enter and leave parallel regions frequently.
When PASSIVE is set, idle threads wait on a mutex in the operating system and consume no CPU time until
being restarted. Passive idle is best when a program has long periods of serial activity or when the program
runs on a multi-user machine or otherwise shares CPU resources.6263
Chapter 6. Using Directives and
Pragmas
It is often useful to be able to alter the effects of certain command line options or default behavior of the
compiler. Fortran directives and C/C++ pragmas provide pragmatic information that control the actions of
the compiler in a particular portion of a program without affecting the program as a whole. That is, while a
command line option affects the entire source file that is being compiled, directives and pragmas apply, or
disable, the effects of a command line option to selected subprograms or to selected loops in the source file,
for example, to optimize a specific area of code. Use directives and pragmas to tune selected routines or loops.
PGI Proprietary Fortran Directives
PGI Fortran compilers support proprietary directives that may have any of the following forms:
!pgi$g directive
!pgi$r directive
!pgi$l directive
!pgi$ directive
Note
If the input is in fixed format, the comment character must begin in column 1 and either * or C is
allowed in place of !.
The scope indicator occurs after the $; this indicator controls the scope of the directive. Some directives
ignore the scope indicator. The valid scopes, shown above, are:
g
(global) indicates the directive applies to the end of the source file.
r
(routine) indicates the directive applies to the next subprogram.
l
(loop) indicates the directive applies to the next loop (but not to any loop contained within the loop
body). Loop-scoped directives are only applied to DO loops.PGI® User’s Guide
64
blank
indicates that the default scope for the directive is applied.
The body of the directive may immediately follow the scope indicator. Alternatively, any number of blanks may
precede the name of the directive. Any names in the body of the directive, including the directive name, may
not contain embedded blanks. Blanks may surround any special characters, such as a comma or an equal
sign.
The directive name, including the directive prefix, may contain upper or lower case letters, and the case is not
significant. Case is significant for any variable names that appear in the body of the directive if the command
line option –Mupcase is selected. For compatibility with other vendors’ directives, the prefix cpgi$ may be
substituted with cdir$ or cvd$.
Note
If the input is in fixed format, the comment character must begin in column 1.
PGI Proprietary C and C++ Pragmas
Pragmas may be supplied in a C/C++ source file to provide information to the compiler. Many pragmas have
a corresponding command-line option. Pragmas may also toggle an option, selectively enabling and disabling
the option.
The general syntax of a pragma is:
#pragma [ scope ] pragma-body
The optional scope field is an indicator for the scope of the pragma; some pragmas ignore the scope indicator.
The valid scopes are:
global
indicates the pragma applies to the entire source file.
routine
indicates the pragma applies to the next function.
loop
indicates the pragma applies to the next loop (but not to any loop contained within the loop body). Loopscoped pragmas are only applied to for and while loops.
If a scope indicator is not present, the default scope, if any, is applied. Whitespace must appear after the
pragma keyword and between the scope indicator and the body of the pragma. Whitespace may also surround
any special characters, such as a comma or an equal sign. Case is significant for the names of the pragmas and
any variable names that appear in the body of the pragma.
PGI Proprietary Optimization Fortran Directive and C/C++ Pragma Summary
The following table summarizes the supported Fortran directives and C/C++ pragmas. The following terms are
useful in understanding the table.Chapter 6. Using Directives and Pragmas
65
• Functionality is a brief summary of the way to use the directive or pragma. For a complete description, refer
to Chapter 17, “Directives and Pragmas Reference,” on page 263.
• Many of the directives and pragmas can be preceded by NO. The default entry indicates the default for the
directive or pragma. N/A appears if a default does not apply.
• The scope entry indicates the allowed scope indicators for each directive or pragma, with L for loop, R for
routine, and G for global. The default scope is surrounded by parentheses and N/A appears if the directive
or pragma is not available in the given language.
Note
The “*” in the scope indicates this:
For routine-scoped directive
The scope includes the code following the directive or pragma until the end of the routine.
For globally-scoped directive
The scope includes the code following the directive or pragma until the end of the file rather
than for the entire file.
The name of a directive or pragma may also be prefixed with –M. For example, the directive –Mbounds is
equivalent to bounds and –Mopt is equivalent to opt; and the pragma –Mnoassoc is equivalent to noassoc, and
–Mvintr is equivalent to vintr.
Table 6.1. Proprietary Optimization-Related Fortran Directive and C/C++ Pragma Summary
Directive or
pragma
Functionality Default Fortran
Scope
C/C++
Scope
altcode
(noaltcode)
Do/don’t generate alternate code for
vectorized and parallelized loops.
altcode (L)RG (L)RG
assoc (noassoc) Do/don’t perform associative
transformations.
assoc (L)RG (L)RG
bounds
(nobounds)
Do/don’t perform array bounds checking. nobounds (R)G* (R)G
cncall (nocncall) Loops are considered for parallelization,
even if they contain calls to user-defined
subroutines or functions, or if their loop
counts do not exceed usual thresholds.
nocncall (L)RG (L)RG
concur
(noconcur)
Do/don’t enable auto-concurrentization of
loops.
concur (L)RG (L)RG
depchk
(nodepchk)
Do/don’t ignore potential data
dependencies.
depchk (L)RG (L)RG
eqvchk
(noeqvchk)
Do/don’t check EQUIVALENCE for data
dependencies.
eqvchk (L)RG N/A
fcon (nofcon) Do/don’t assume unsuffixed real constants
are single precision.
nofcon N/A (R)GPGI® User’s Guide
66
Directive or
pragma
Functionality Default Fortran
Scope
C/C++
Scope
invarif (noinvarif) Do/don’t remove invariant if constructs
from loops.
invarif (L)RG (L)RG
ivdep Ignore potential data dependencies. ivdep (L)RG N/A
lstval (nolstval) Do/don’t compute last values. lstval (L)RG (L)RG
opt Select optimization level. N/A (R)G (R)G
safe (nosafe) Do/don’t treat pointer arguments as safe. safe N/A (R)G
safe_lastval Parallelize when loop contains a scalar
used outside of loop.
not enabled (L) (L)
safeptr (nosafeptr) Do/don’t ignore potential data
dependencies to pointers.
nosafeptr N/A L(R)G
single (nosingle) Do/don’t convert float parameters to
double.
nosingle N/A (R)G*
tp Generate PGI Unified Binary code
optimized for specified targets.
N/A (R)G (R)G
unroll (nounroll) Do/don’t unroll loops. nounroll (L)RG (L)RG
vector (novector) Do/don't perform vectorizations. vector (L)RG* (L)RG
vintr (novintr) Do/don’t recognize vector intrinsics. vintr (L)RG (L)RG
Scope of Fortran Directives and Command-Line options
During compilation the effect of a directive may be to either turn an option on, or turn an option off. Directives
apply to the section of code following the directive, corresponding to the specified scope, which may include
the following loop, the following routine, or the rest of the program. This section presents several examples
that show the effect of directives as well as their scope.
Consider the following Fortran code:
integer maxtime, time
parameter (n = 1000, maxtime = 10)
double precision a(n,n), b(n,n), c(n,n)
do time = 1, maxtime
do i = 1, n
do j = 1, n
c(i,j) = a(i,j) + b(i,j)
enddo
enddo
enddo
end
When compiled with –Mvect, both interior loops are interchanged with the outer loop.
$ pgf95 -Mvect dirvect1.f
Directives alter this behavior either globally or on a routine or loop by loop basis. To assure that vectorization
is not applied, use the novector directive with global scope.Chapter 6. Using Directives and Pragmas
67
cpgi$g novector
integer maxtime, time
parameter (n = 1000, maxtime = 10)
double precision a(n,n), b(n,n), c(n,n)
do time = 1, maxtime
do i = 1, n
do j = 1, n
c(i,j) = a(i,j) + b(i,j)
enddo
enddo
enddo
end
In this version, the compiler disables vectorization for the entire source file. Another use of the directive
scoping mechanism turns an option on or off locally, either for a specific procedure or for a specific loop:
integer maxtime, time
parameter (n = 1000, maxtime = 10)
double precision a(n,n), b(n,n), c(n,n)
cpgi$l novector
do time = 1, maxtime
do i = 1, n
do j = 1, n
c(i,j) = a(i,j) + b(i,j)
enddo
enddo
enddo
end
Loop level scoping does not apply to nested loops. That is, the directive only applies to the following loop.
In this example, the directive turns off vector transformations for the top-level loop. If the outer loop were a
timing loop, this would be a practical use for a loop-scoped directive.
Scope of C/C++ Pragmas and Command-Line Options
During compilation a pragma either turns an option on or turns an option off. Pragmas apply to the section
of code corresponding to the specified scope - either the entire file, the following loop, or the following or
current routine. This section presents several examples showing the effect of pragmas and the use of the
pragma scope indicators.
Note
In all cases, pragmas override a corresponding command-line option.
For pragmas that have only routine and global scope, there are two rules for determining the scope of a
pragma. We cover these special scope rules at the end of this section. Consider the program:
main() {
float a[100][100], b[100][100], c[100][100];
int time, maxtime, n, i, j;
maxtime=10;
n=100;
for (time=0; time[,[,...]]
where is any valid variable, member, or array element reference.PGI® User’s Guide
70
Format Requirements
NOTE
The sentinel for prefetch directives is c$mem, which is distinct from the cpgi$ sentinel used for
optimization directives. Any prefetch directives that use the cpgi$ sentinel will be ignored by the PGI
compilers.
• The "c" must be in column 1.
• Either * or ! is allowed in place of c.
• The scope indicators g, r and l used with the cpgi$ sentinel are not supported.
• The directive name, including the directive prefix, may contain upper or lower case letters and is case
insensitive (case is not significant).
• Any variable names that appear in the body of the directive are case sensitive if the command line option
–Mupcase is selected.
Sample Usage
Example 6.1. Prefetch Directive Use
This example uses prefetch directives to prefetch data in a matrix multiplication inner loop where a row of one
source matrix has been gathered into a contiguous vector.
real*8 a(m,n), b(n,p), c(m,p), arow(n)
...
do j = 1, p
c$mem prefetch arow(1),b(1,j)
c$mem prefetch arow(5),b(5,j)
c$mem prefetch arow(9),b(9,j)
do k = 1, n, 4
c$mem prefetch arow(k+12),b(k+12,j)
c(i,j) = c(i,j) + arow(k) * b(k,j)
c(i,j) = c(i,j) + arow(k+1) * b(k+1,j)
c(i,j) = c(i,j) + arow(k+2) * b(k+2,j)
c(i,j) = c(i,j) + arow(k+3) * b(k+3,j)
enddo
enddo
This pattern of prefetch directives causes the compiler to emit prefetch instructions whereby elements of arow
and b are fetched into the data cache starting four iterations prior to first use. By varying the prefetch distance
in this way, it is sometimes possible to reduce the effects of main memory latency and improve performance.
!DEC$ Directive
PGI Fortran compilers for Microsoft Windows support several de-facto standard Fortran directives that help
with interlanguage calling and importing and exporting routines to and from DLLs. These directives all take the
form:
!DEC$ directiveChapter 6. Using Directives and Pragmas
71
Format Requirements
You must follow the following format requirements for the directive to be recognized in your program:
• The directive must begin in line 1 when the file is fixed format or compiled with –Mfixed.
• The directive prefix !DEC$ requires a space between the prefix and the directive keyword ATTRIBUTES.
• The ! must begin the prefix when compiling Fortran 90 freeform format.
• The characters C or * can be used in place of ! in either form of the prefix when compiling fixed-form (F77-
style) format.
• The directives are completely case insensitive.
ALIAS Directive
This directive specifies an alternative name with which to resolve a routine.
The syntax for the ALIAS directive is either of the following:
!DEC$ ALIAS routine_name , external_name
!DEC$ ALIAS routine_name : external_name
In this syntax, external_name is used as the external name for the specified routine_name.
If external_name is an identifier name, the name (in uppercase) is used as the external name for the
specified routine_name. If external_name is a character constant, it is used as-is; the string is not
changed to uppercase, nor are blanks removed.
You can also supply an alias for a routine using the ATTRIBUTES directive, described in the next section:
!DEC$ ATTIRIBUTES ALIAS : 'alias_name' :: routine_name
This directive specifies an alternative name with which to resolve a routine, as illustrated in the following code
fragment that provides external names for three routines. In this fragment, the external name for sub1 is
name1, for sub2 is name2, and for sub3 is name3.
subroutine sub
!DEC$ alias sub1 , 'name1'
!DEC$ alias sub2 : 'name2'
!DEC$ attributes alias : 'name3' :: sub3
ATTRIBUTES Directive
!DEC$ ATTRIBUTES
where is one of:
ALIAS : 'alias_name' :: routine_name
Specifies an alternative name with which to resolve routine_name.
C :: routine_name
Specifies that the routine routine_name will have its arguments passed by value. When a routine
marked C is called, arguments, except arrays, are sent by value. For characters, only the first character is
passed. The standard Fortran calling convention is pass by reference.PGI® User’s Guide
72
DLLEXPORT :: name
Specifies that 'name' is being exported from a DLL.
DLLIMPORT :: name
Specifies that 'name' is being imported from a DLL.
REFERENCE :: name
Specifies that the argument 'name' is being passed by reference. Often this attribute is used in conjunction
with STDCALL, where STDCALL refers to an entire routine; then individual arguments are modified with
REFERENCE.
STDCALL :: routine_name
Specifies that routine 'routine_name' will have its arguments passed by value. When a routine marked
STDCALL is called, arguments (except arrays and characters) will be sent by value. The standard Fortran
calling convention is pass by reference.
VALUE :: name
Specifies that the argument 'name' is being passed by value.
DISTRIBUTE Directive
The syntax for the DISTRIBUTE directive is either of the following:
!DEC$ DISTRIBUTE POINT
!DEC$ DISTRIBUTEPOINT
This directive is front-end based, and tells the compiler at what point within a loop to split into two loops.
subroutine dist(a,b,n)
integer i
integer n
integer a(*)
integer b(*)
do i = 1,n
a(i) = a(i)+2
!DEC$ DISTRIBUTE POINT
b(i) = b(i)*4
enddo
end subroutine
ALIAS Directive
!DEC$ ALIAS
is the same as !DEC$ ATTRIBUTES ALIAS
C$PRAGMA C
When programs are compiled using one of the PGI Fortran compilers on Linux, Win64, OSX, and SUA systems,
an underscore is appended to Fortran global names, including names of functions, subroutines, and common
blocks. This mechanism distinguishes Fortran name space from C/C++ name space.
You can use C$PRAGMA C in the Fortran program to call a C/C++ function from Fortran. The statement would
look similar to this:Chapter 6. Using Directives and Pragmas
73
C$PRAGMA C(name[,name]...)
NOTE
This statement directs the compiler to recognize the routine 'name' as a C function, thus preventing
the Fortran compiler from appending an underscore to the routine name.
On Win32 systems the C$PRAGMA C as well as the attributes C and STDCALL may effect other changes on
argument passing as well as on the names of the routine. For more information on this topic, refer to “Win32
Calling Conventions,” on page 120.7475
Chapter 7. Creating and Using
Libraries
A library is a collection of functions or subprograms that are grouped for reference and ease of linking. This
chapter discusses issues related to PGI-supplied compiler libraries. Specifically, it addresses the use of C/C++
builtin functions in place of the corresponding libc routines, creation of dynamically linked libraries, known as
shared objects or shared libraries, and math libraries.
Note
This chapter does not duplicate material related to using libraries for inlining, described in “Creating
an Inline Library,” on page 47 or information related to run-time library routines available to OpenMP
programmers, described in “Run-time Library Routines,” on page 55.
This chapter has examples that include the following options related to creating and using libraries.
–Bdynamic –fpic –Mmakeimplib
–Bstatic –implib –o
–c –l –shared
–def –Mmakedll
Using builtin Math Functions in C/C++
The name of the math header file is math.h. Include the math header file in all of your source files that use a
math library routine as in the following example, which calculates the inverse cosine of pi/3.
#include
#define PI 3.1415926535
void main()
{
double x, y;
x = PI/3.0;
y = acos(x);
}PGI® User’s Guide
76
Including math.h will cause PGCC C and C++ to use builtin functions, which are much more efficient
than library calls. In particular, the following intrinsics calls will be processed using builtins if you include
math.h:
abs atan atan2 cos
exp fabs fmax fmaxf
fmin fminf log log10
pow sin sqrt tan
Creating and Using Shared Object Files on Linux
All of the PGI Fortran, C, and C++ compilers support creation of shared object files. Unlike statically linked
object and library files, shared object files link and resolve references with an executable at runtime via a
dynamic linker supplied with your operating system. The PGI compilers must generate position independent
code to support creation of shared objects by the linker. However, this is not the default. You must create
object files with position independent code and shared object files that will include them.
The following steps describe how to create and use a shared object file.
1. Create an object file with position independent code.
To do this, compile your code with the appropriate PGI compiler using the –fpic option, or one of the
equivalent options, such as –fPIC, –Kpic, and –KPIC, which are supported for compatibility with
other systems. For example, use the following command to create an object file with position independent
code using pgf95:
% pgf95 -c -fpic tobeshared.f
2. Produce a shared object file.
To do this, use the appropriate PGI compiler to invoke the linker supplied with your system. It is customary
to name such files using a .so filename extension. On Linux, you do this by passing the –shared option
to the linker:
% pgf95 -shared -o tobeshared.so tobeshared.o
Note
Compilation and generation of the shared object can be performed in one step using both the
–fpic option and the appropriate option for generation of a shared object file.
3. Use a shared object file.
To do this, us the appropriate PGI compiler to compile and link the program which will reference functions
or subroutines in the shared object file, and list the shared object on the link line, as shown here:
% pgf95 -o myprog myprog.f tobeshared.so
4. Make the executable available.
You now have an executable myprog which does not include any code from functions or
subroutines in tobeshared.so, but which can be executed and dynamically linked to that code.Chapter 7. Creating and Using Libraries
77
By default, when the program is linked to produce myprog, no assumptions are made on the
location of tobeshared.so. Therefore, for myprog to execute correctly, you must initialize the
environment variable LD_LIBRARY_PATH to include the directory containing tobeshared.so.
If LD_LIBRARY_PATH is already initialized, it is important not to overwrite its contents. Assuming
you have placed tobeshared.so in a directory /home/myusername/bin, you can initialize
LD_LIBRARY_PATH to include that directory and preserve its existing contents, as shown in the following:
% setenv LD_LIBRARY_PATH "$LD_LIBRARY_PATH":/home/myusername/bin
If you know that tobeshared.so will always reside in a specific directory, you can create the executable
myprog in a form that assumes this using the –R link-time option. For example, you can link as follows:
% pgf95 -o myprog myprof.f tobeshared.so -R/home/myusername/bin
Note
As with the –L option, there is no space between –R and the directory name.
If the –R option is used, it is not necessary to initialize LD_LIBRARY_PATH. In the previous
example, the dynamic linker will always look in /home/myusername/bin to resolve references to
tobeshared.so. By default, if the LD_LIBRARY_PATH environment variable is not set, the linker will
only search /usr/lib and /lib for shared objects.
The command ldd is a useful tool when working with shared object files and executables that reference
them. When applied to an executable, as shown in the following example, ldd lists all shared object files
referenced in the executable along with the pathname of the directory from which they will be extracted.
% ldd myprog
If the pathname is not hard-coded using the–R option, and if LD_LIBRARY_PATH is not initialized, the
pathname is listed as “not found”. For more information on ldd, its options and usage, see the online man
page for ldd.
Creating and Using Shared Object Files in SFU and 32-bit SUA
Note
The information included in this section is valid for 32-bit only.
The 32-bit version of PGI Workstation for SFU and SUA uses the GNU ld for its linker, unlike previous versions
that used the Windows LINK.EXE. With this change, the PGI compilers and tools for SFU and 32-bit SUA are
now able to generate shared object (.so) files. You use the –shared switch to generate a shared object file.
The following example creates a shared object file, hello.so, and then creates a program called hello that
uses it.
1. Create a shared object file.
To produce a shared object file, use the appropriate PGI compiler to invoke the linker supplied with your
system. It is customary to name such files using a .so filename extension. In the following example, we use
hello.so:PGI® User’s Guide
78
% pgcc -shared hello.c -o hello.so
2. Create a program that uses the shared object, in this example, hello.so:
% pgcc hi.c hello.so -o hello
Shared Object Error Message
When running a program that uses a shared object, you may encounter an error message similar to the
following:
hello: error in loading shared libraries hello.so:
cannot open shared object file: No such file or directory
This error message either means that the shared object file does not exist or that the location of this file is not
specified in your LD_LIBRARY_PATH variable. To specify the location of the .so, add the shared object’s
directory to your LD_LIBRARY_PATH variable. For example, the following command adds the current
directory to your LD_LIBRARY_PATH variable using C shell syntax:
% setenv LD_LIBRARY_PATH "$LD_LIBRARY_PATH":"./"
Shared Object-Related Compiler Switches
The following switches support shared object files in SFU and SUA. For more detailed information on these
switches, refer to Chapter 15, “Command-Line Options Reference,” on page 163.
–shared
Used to produce shared libraries
–Bdynamic
Passed to linker; specify dynamic binding
Note
On Windows, -Bstatic and -Bdynamic must be used for both compiling and linking.
–Bstatic
Passed to linker; specify static binding
–Bstatic_pgi
Use to link static PGI libraries with dynamic system libraries; implies –Mnorpath.
–L
Passed to linker; add directory to library search path.
–Mnorpath
Don't add –rpath paths to link line.
–Mnostartup
Do not use standard linker startup file.
–Mnostdlib
Do not use standard linker libraries.
–R
Passed to linker; just link symbols from object, or add directory to run time search path.Chapter 7. Creating and Using Libraries
79
PGI Runtime Libraries on Windows
The PGI runtime libraries on Windows are available in both static and dynamicallyy-linked (DLL) versions. The
static libraries are used by default.
• You can use the dynamically-linked version of the routine by specifying –Bdynamic at both compile and
link time.
• You can explicitly specify static linking, the default, by using -Bstatic at compile and link time.
For details on why you might choose one type of linking over another type, refer to “Creating and Using
Dynamic-Link Libraries on Windows,” on page 80.
Creating and Using Static Libraries on Windows
The Microsoft Library Manager (LIB.EXE) is the tool that is typically used to create and manage a static
library of object files on Windows. LIB is provided with the PGI compilers as part of the Microsoft Open Tools.
Refer to www.msdn2.com for a complete LIB reference - searching for LIB.EXE. For a list of available
options, invoke LIB with the /? switch.
For compatibility with legacy makefiles, PGI provides wrappers for LIB and LINK called ar. This version of ar
is compatible with Womdpws amd pbject-file formats.
PGi also provides ranlib as a placeholder for legacy makefile support.
ar command
The ar command is a legacy archive wrapper that interprets legacy ar command line options and translates
these to LINK/LIB options. You can use it to create libraries of object files.
Syntax:
The syntax for the ar command is this:
ar [options] [archive] [object file].
Where:
• The first argument must be a command line switch, and the leading dash on the first option is optional.
• The single character options, such as –d and –v, may be combined into a single option, as –dv.
Thus, ar dv, ar -dv, and ar -d -v all mean the same thing.
• The first non-switch argument must be the library name.
• One (and only one) of –d, –r, –t, or –x must appear on the command line.
Options
The options available for the ar command are these:PGI® User’s Guide
80
–c
This switch is for compatibility; it is ignored.
–d
The named object files are deleted from the library.
–r
The named object files are replaced in or added to the library.
ranlib command
The ranlib command is a wrapper that allows use of legacy scripts and makefiles that use the ranlib
command. The command actually does nothing; it merely exists for compatibility.
Syntax:
The syntax for the ranlib command is this:
DOS> ranlib [options] [archive]
Options
The options available for the ranlib command are these:
–help
Short help information is printed out.
–V
Version information is printed out.
Creating and Using Dynamic-Link Libraries on Windows
There are several differences between static and dynamic-link libraries on Windows. Libraries of either
type are used when resolving external references for linking an executable, but the process differs for each
type of library. When linking with a static library, the code needed from the library is incorporated into
the executable. When linking with a DLL, external references are resolved using the DLL's import library,
not the DLL itself. The code in the DLL associated with the external references does not become a part of
the executable. The DLL is loaded when the executable that needs it is run. For the DLL to be loaded in this
manner, the DLL must be in your path.
Static libraries and DLLs also handle global data differently. Global data in static libraries is automatically
accessible to other objects linked into an executable. Global data in a DLL can only be accessed from
outside the DLL if the DLL exports the data and the image that uses the data imports it. To this end
the C compilers support the Microsoft storage class extensions __declspec(dllimport) and
__declspec(dllexport). These extensions may appear as storage class modifiers and enable functions
and data to be imported and exported:
extern int __declspec(dllimport)
intfunc();
float __declspec(dllexport) fdata;Chapter 7. Creating and Using Libraries
81
The PGI Fortran compilers support the DEC$ATTRIBUTES extensions DLLIMPORT and DLLEXPORT:
cDEC$ ATTRIBUTES DLLEXPORT :: object [,object] ...
cDEC$ ATTRIBUTES DLLIMPORT :: object [,object] ...
Here c is one of C, c, !, or *. object is the name of the subprogram or common block that is exported or
imported. Note that common block names are enclosed within slashes (/). In example:
cDEC$ ATTRIBUTES DLLIMPORT :: intfunc
!DEC$ ATTRIBUTES DLLEXPORT :: /fdata/
For more information on these extensions, refer to “!DEC$ Directive,” on page 70.
The Examples in this section further illustrate the use of these extensions.
To create a DLL from the command line, use the –Mmakedll option.
The following switches apply to making and using DLLs with the PGI compilers:
–Bdynamic
Compile for and link to the DLL version of the PGI runtime libraries. This flag is required when linking
with any DLL built by the PGI compilers. This flag corresponds to the /MD flag used by Microsoft’s cl
compilers.
–Bstatic
Compile for and link to the static version of the PGI runtime libraries. This flag corresponds to the /MT
flag used by Microsoft’s cl compilers.
–Mmakedll
Generate a dynamic-link library or DLL. Implies –Bdynamic.
–Mmakeimplib
Generate an import library without generating a DLL. Use this flag when you want to generate an import
library for a DLL but are not yet ready to build the DLL itself. This situation might arise, for example, when
building DLLs with mutual imports, as shown in Example 7.4, “Build DLLs Containing Circular Mutual
Imports: Fortran,” on page 86.
–o
Passed to the linker. Name the DLL or import library .
–def
When used with –Mmakedll, this flag is passed to the linker and a .def file named is generated
for the DLL. The .def file contains the symbols exported by the DLL. Generating a .def file is not
required when building a DLL but can be a useful debugging tool if the DLL does not contain the symbols
that you expect it to contain.
When used with –Mmakeimplib, this flag is passed to lib which requires a .def file to create an import
library. The .def file can be empty if the list of symbols to export are passed to lib on the command line
or explicitly marked as dllexport in the source code.
–implib
Passed to the linker. Generate an import library named for the DLL. A DLL’s import library is the
interface used when linking an executable that depends on routines in a DLL.PGI® User’s Guide
82
To use the PGI compilers to create an executable that links to the DLL form of the runtime, use the compiler
flag –Bdynamic. The executable built will be smaller than one built without –Bdynamic; the PGI runtime
DLLs, however, must be available on the system where the executable is run. The –Bdynamic flag must be
used when an executable is linked against a DLL built by the PGI compilers.
The following examples outline how to use –Bdynamic, –Mmakedll and –Mmakeimplib to build and use
DLLs with the PGI compilers.
Example 7.1. Build a DLL: Fortran
In this example we build a DLL out of a single source file, object1.f, which exports data and a subroutine
using DLLEXPORT. The main source file, prog1.f, uses DLLIMPORT to import the data and subroutine
from the DLL.
object1.f
subroutine sub1(i)
!DEC$ ATTRIBUTES DLLEXPORT :: sub1
integer i
common /acommon/ adata
integer adata
!DEC$ ATTRIBUTES DLLEXPORT :: /acommon/
print *, "sub1 adata", adata
print *, "sub1 i ", i
adata = i
end
prog1.f
program prog1
common /acommon/ adata
integer adata
external sub1
!DEC$ ATTRIBUTES DLLIMPORT:: sub1, /acommon/
adata = 11
call sub1(12)
print *, "main adata", adata
end
Step 1: Create the DLL obj1.dll and its import library obj1.lib using the following series of commands:
% pgf95 -Bdynamic -c object1.f
% pgf95 -Mmakedll object1.obj -o obj1.dll
Step 2: Compile the main program:
% pgf95 -Bdynamic -o prog1 prog1.f -defaultlib:obj1
The –Mdll switch causes the compiler to link against the PGI runtime DLLs instead of the PGI runtime static
libraries. The –Mdll switch is required when linking against any PGI-compiled DLL, such as obj1.dll. The
#defaultlib: switch specifies that obj1.lib, the DLL’s import library, should be used to resolve imports.
Step 3: Ensure that obj1.dll is in your path, then run the executable prog1 to determine if the DLL was
successfully created and linked:Chapter 7. Creating and Using Libraries
83
% prog1
sub1 adata 11
sub1 i 12
main adata 12
Should you wish to change obj1.dll without changing the subroutine or function interfaces, no rebuilding
of prog1 is necessary. Just recreate obj1.dll and the new obj1.dll is loaded at runtime.
Example 7.2. Build a DLL: C
In this example, we build a DLL out of a single source file, object2.c, which exports data and a subroutine
using __declspec(dllexport). The main source file, prog2.c, uses __declspec(dllimport) to
import the data and subroutine from the DLL.
object2.c
int __declspec(dllexport) data;
void __declspec(dllexport)
func2(int i)
{
printf("func2: data == %d\n", data);
printf("func2: i == %d\n", i);
data = i;
}
prog2.c
int __declspec(dllimport) data;
void __declspec(dllimport) func2(int);
int
main()
{
data = 11;
func2(12);
printf("main: data == %d\n",data);
return 0;
}
Step 1: Create the DLL obj2.dll and its import library obj2.lib using the following series of commands:
% pgcc -Bdynamic -c object2.c
% pgcc -Mmakedll object2.obj -o obj2.dll
Step 2: Compile the main program:
% pgcc -Bdynamic -o prog2 prog2.c -defaultlib:obj2
The –Bdynamic switch causes the compiler to link against the PGI runtime DLLs instead of the PGI runtime
static libraries. The –Bdynamic switch is required when linking against any PGI-compiled DLL such as
obj2.dll. The #defaultlib: switch specifies that obj2.lib, the DLL’s import library, should be used
to resolve the imported data and subroutine in prog2.c.
Step 3: Ensure that obj2.dll is in your path, then run the executable prog2 to determine if the DLL was
successfully created and linked:PGI® User’s Guide
84
% prog2
func2: data == 11
func2: i == 12
main: data == 12
Should you wish to change obj2.dll without changing the subroutine or function interfaces, no rebuilding
of prog2 is necessary. Just recreate obj2.dll and the new obj2.dll is loaded at runtime.
Example 7.3. Build DLLs Containing Circular Mutual Imports: C
In this example we build two DLLs, obj3.dll and obj4.dll, each of which imports a routine that is
exported by the other. To link the first DLL, the import library for the second DLL must be available. Usually an
import library is created when a DLL is linked. In this case, however, the second DLL cannot be linked without
the import library for the first DLL. When such circular imports exist, an import library for one of the DLLs
must be created in a separate step without creating the DLL. The PGI drivers call the Microsoft lib tool to
create import libraries in this situation. Once the DLLs are built, we can use them to build the main program.
/* object3.c */
void __declspec(dllimport) func_4b(void);
void __declspec(dllexport)
func_3a(void)
{
printf("func_3a, calling a routine in obj4.dll\n");
func_4b();
}
void __declspec(dllexport)
func_3b(void)
{
printf("func_3b\n");
}
/* object4.c */
void __declspec(dllimport) func_3b(void);
void __declspec(dllexport)
func_4a(void)
{
printf("func_4a, calling a routine in obj3.dll\n");
func_3b();
}
void __declspec(dllexport)
func_4b(void)
{
printf("func_4b\n");
}
/* prog3.c */
void __declspec(dllimport) func_3a(void);
void __declspec(dllimport) func_4a(void);
int
main()
{
func_3a();
func_4a();
return 0;
}Chapter 7. Creating and Using Libraries
85
Step 1: Use –Mmakeimplib with the PGI compilers to build an import library for the first DLL without
building the DLL itself.
% pgcc -Bdynamic -c object3.c
% pgcc -Mmakeimplib -o obj3.lib object3.obj
The –def= option can also be used with –Mmakeimplib. Use a .def file when you need to
export additional symbols from the DLL. A .def file is not needed in this example because all symbols are
exported using __declspec(dllexport).
Step 2: Use the import library, obj3.lib, created in Step 1, to link the second DLL.
% pgcc -Bdynamic -c object4.c
% pgcc -Mmakedll -o obj4.dll object4.obj -defaultlib:obj3
Step 3: Use the import library, obj4.lib, created in Step 2, to link the first DLL.
% pgcc -Mmakedll -o obj3.dll object3.obj -defaultlib:obj4
Step 4: Compile the main program and link against the import libraries for the two DLLs.
% pgcc -Bdynamic prog3.c -o prog3 -defaultlib:obj3 -defaultlib:obj4
Step 5: Execute prog3.exe to ensure that the DLLs were create properly.
% prog3
func_3a, calling a routine in obj4.dll
func_4b
func_4a, calling a routine in obj3.dll
func_3bPGI® User’s Guide
86
Example 7.4. Build DLLs Containing Circular Mutual Imports: Fortran
In this example we build two DLLs when each DLL is dependent on the other, and use them to build the main
program. In the following source files, object2.f95 makes calls to routines defined in object3.f95, and vice
versa. This situation of mutual imports requires two steps to build each DLL.
In this example we build two DLLs, obj2.dll and obj3.dll, each of which imports a routine that is
exported by the other. To link the first DLL, the import library for the second DLL must be available. Usually an
import library is created when a DLL is linked. In this case, however, the second DLL cannot be linked without
the import library for the first DLL. When such circular imports exist, an import library for one of the DLLs
must be created in a separate step without creating the DLL. The PGI drivers call the Microsoft lib tool to
create import libraries in this situation. Once the DLLs are built, we can use them to build the main program.
object2.f95
subroutine func_2a
external func_3b
!DEC$ ATTRIBUTES DLLEXPORT :: func_2a
!DEC$ ATTRIBUTES DLLIMPORT :: func_3b
print*,"func_2a, calling a routine in obj3.dll"
call func_3b()
end subroutine
subroutine func_2b
!DEC$ ATTRIBUTES DLLEXPORT :: func_2b
print*,"func_2b"
end subroutine
object3.f95
subroutine func_3a
external func_2b
!DEC$ ATTRIBUTES DLLEXPORT :: func_3a
!DEC$ ATTRIBUTES DLLIMPORT :: func_2b
print*,"func_3a, calling a routine in obj2.dll"
call func_2b()
end subroutine
subroutine func_3b
!DEC$ ATTRIBUTES DLLEXPORT :: func_3b
print*,"func_3b"
end subroutine
prog2.f95
program prog2
external func_2a
external func_3a
!DEC$ ATTRIBUTES DLLIMPORT :: func_2a
!DEC$ ATTRIBUTES DLLIMPORT :: func_3a
call func_2a()
call func_3a()
end program
Step 1: Use –Mmakeimplib with the PGI compilers to build an import library for the first DLL without
building the DLL itself.
% pgf95 -Bdynamic -c object2.f95
% pgf95 -Mmakeimplib -o obj2.lib object2.objChapter 7. Creating and Using Libraries
87
Tip
The -def= option can also be used with -Mmakeimplib. Use a .def file when you need to
export additional symbols from the DLL. A .def file is not needed in this example because all symbols
are exported using DLLEXPORT.
Step 2: Use the import library, obj2.lib, created in Step 1, to link the second DLL.
% pgf95 -Bdynamic -c object3.f95
% pgf95 -Mmakedll -o obj3.dll object3.obj -defaultlib:obj2
Step 3: Use the import library, obj3.lib, created in Step 2, to link the first DLL.
% pgf95 -Mmakedll -o obj2.dll object2.obj -defaultlib:obj3
Step 4: Compile the main program and link against the import libraries for the two DLLs.
% pgf95 -Bdynamic prog2.f95 -o prog2 -defaultlib:obj2 -defaultlib:obj3
Step 5: Execute prog2 to ensure that the DLLs were created properly:
% prog2
func_2a, calling a routine in obj3.dll
func_3b
func_3a, calling a routine in obj2.dll
func_2b
Example 7.5. Import a Fortran module from a DLL
In this example we import a Fortran module from a DLL. We use the source file my_module_def.f90 to
create a DLL containing a Fortran module. We then use the source file my_module_use.f90 to build a
program that imports and uses the Fortran module from my_module_def.f90.
defmod.f90
module testm
type a_type
integer :: an_int
end type a_type
type(a_type) :: a, b
!DEC$ ATTRIBUTES DLLEXPORT :: a,b
contains
subroutine print_a
!DEC$ ATTRIBUTES DLLEXPORT :: print_a
write(*,*) a%an_int
end subroutine
subroutine print_b
!DEC$ ATTRIBUTES DLLEXPORT :: print_b
write(*,*) b%an_int
end subroutine
end module
usemod.f90
use testm
a%an_int = 1
b%an_int = 2
call print_a
call print_b
endPGI® User’s Guide
88
Step 1: Create the DLL.
% pgf90 -Mmakedll -o defmod.dll defmod.f90
Creating library defmod.lib and object defmod.exp
Step 2: Create the exe and link against the import library for the imported DLL.
% pgf90 -Bdynamic -o usemod usemod.f90 -defaultlib:defmod.lib
Step 3: Run the exe to ensure that the module was imported from the DLL properly.
% usemod
1
2
Using LIB3F
The PGI Fortran compilers include complete support for the de facto standard LIB3F library routines on both
Linux and Windows operating systems. See the PGI Fortran Reference manual for a complete list of available
routines in the PGI implementation of LIB3F.
LAPACK, BLAS and FFTs
Pre-compiled versions of the public domain LAPACK and BLAS libraries are included with the PGI compilers.
The LAPACK library is called liblapack.a or on Windows, liblapack.lib. The BLAS library is called
libblas.a or on Windows, libblas.lib. These libraries are installed to $PGI//lib, where
is replaced with the appropriate target name (linux86, linux86-64, osx86, osx86-64, win32, win64,
sfu32, sua32, or sua64).
To use these libraries, simply link them in using the –l option when linking your main program:
% pgf95 myprog.f -llapack -lblas
Highly optimized assembly-coded versions of BLAS and certain FFT routines may be available for your
platform. In some cases, these are shipped with the PGI compilers. See the current release notes for the PGI
compilers you are using to determine if these optimized libraries exist, where they can be downloaded (if
necessary), and how to incorporate them into your installation as the default.
The C++ Standard Template Library
The PGC++ compiler includes a bundled copy of the STLPort Standard C++ Library. See the online Standard
C++ Library tutorial and reference manual at www.stlport.com for further details and licensing.89
Chapter 8. Using Environment
Variables
Environment variables allow you to set and pass information that can alter the default behavior of the PGI
compilers and the executables which they generate. This chapter includes explanations of the environment
variables specific to PGI compilers. Other environment variables are referenced and documented in other
sections of this User’s Guide or the PGI Tools Guide.
• You use OpenMP environment variables to control the behavior of OpenMP programs. For consistency
related to the OpenMP environment, the details of the OpenMP-related environment variables are included
in Chapter 5, “Using OpenMP”.
• You can use environment variables to control the behavior of the PGDBG debugger or PGPROF profiler. For
a description of environment variables that affect these tools, refer to the PGI Tools Guide.
Setting Environment Variables
Before we look at the environment variables that you might use with the PGI compilers and tools, let’s take a
look at how to set environment variables. To illustrate how to set these variables in various environments, lets
look at how a user might initialize the shell environment prior to using the PGI compilers and tools.
Setting Environment Variables on Linux
Let’s assume that you want access to the PGI products when you log on. Let’s further assume that you installed
the PGI compilers in /opt/pgi and that the license file is in /opt/pgi/license.dat. For access at
startup, you can add the following lines to your startup file.
In csh, use these commands:
% setenv PGI /opt/pgi
% setenv MANPATH "$MANPATH":$PGI/linux86/7.1/man
% setenv LM_LICENSE_FILE $PGI/license.dat
% set path = ($PGI/linux86/7.1/bin $path)
In bash, sh or ksh, use these commands:
% PGI=/opt/pgi; export PGI PGI® User’s Guide
90
% MANPATH=$MANPATH:$PGI/linux86/7.1/man; export MANPATH
% LM_LICENSE_FILE=$PGI/license.dat; export LM_LICENSE_FILE
% PATH=$PGI/linux86/7.1/bin:$PATH; export PATH
Setting Environment Variables on Windows
In Windows, when you access PGI Workstation 7.1 (Start | PGI Workstation 7.1), you have two options that
PGI provides for setting your environment variables - either the DOS command environment or the Cygwin
Bash environment. When you open either of these shells available to you, the default environment variables are
already set and available to you.
You may want to use other environment variables, such as the OpenMP ones. This section explains how to do
that.
Suppose that your home directory is C:tmp. The following examples show how you might set the temporary
directory to your home directory, and then verify that it is set.
Command prompt:
From PGI Workstation 7.1, select PGI Workstation Tools | PGI Command Prompt (32-bit or 64-bit), and
enter the following:
DOS> set TMPDIR=C:tmp
DOS> echo %TMPDIR%
C:\tmp
DOS>
Cygwin Bash prompt:
From PGI Workstation 7.1, select PGI Workstation (32-bit or 64-bit) and at the Cygwin Bash prompt, enter the
following
PGI$ export TMPDIR=C:\\tmp
PGI$ echo $TMPDIR
C:\tmp
PGI$
Setting Environment Variables on Mac OSX
Let’s assume that you want access to the PGi products when you log on. Let’s further assume that you installed
the PGI compilers in /opt/pgi and that the license file is in /opt/pgi/license.dat. For access at
startup, you can add the following lines to your startup file.
For x64 osx86-64 in a csh:
% set path = (/opt/pgi/osx86-64/7.0/bin $path)
% setenv MANPATH "$MANPATH":/opt/pgi/osx86-64/7.0/man
For x64 osx86-64 in a bash, zsh, or ksh:
% PATH=/opt/pgi/osx86-64/7.0/bin:$PATH; export PATH
% MANPATH=$MANPATH:/opt/pgi/osx86-64/7.0/man; export MANPATH
For x64 osx86 in a csh:
% set path = (/opt/pgi/osx86/7.0/bin $path)Chapter 8. Using Environment Variables
91
% setenv MANPATH "$MANPATH":/opt/pgi/osx86/7.0/man
For x64 osx86 in a bash, zsh, or ksh:
% PATH=/opt/pgi/osx86/7.0/bin:$PATH
% export PATH
% MANPATH=$MANPATH:/opt/pgi/osx86/7.0/man
% export MANPATH
PGI-Related Environment Variables
For easy reference, the following summary table provides a quick listing of the OpenMP and PGI compilerrelated environment variables. Later in this chapter are more detailed descriptions of the environment
variables specific to PGI compilers and the executables they generate.
Table 8.1. PGI-related Environment Variable Summary Table
Environment Variable Description
FLEXLM_BATCH (Windows only) When set to 1, prevents interactive pop-ups from
appearing by sending all licensing errors and warnings to standard
out rather than to a pop-up window.
FORTRAN_OPT Allows the user to specify that the PGI Fortran compilers user VAX I/
O conventions.
GMON_OUT_PREFIX Specifies the name of the output file for programs tha are compiler
and linked with the –pg option.
LD_LIBRARY_PATH Specifies a colon-separated set of directories where libraries should
first be searched, prior to searching the standard set of directories.
LM_LICENSE_FILE Specifies the full path of the license file that is required for running
the PGI software. On Windows, LM_LICENSE _FILE does not
need to be set.
MANPATH Sets the directories that are seacrhed for manual pages associated
with the command that the user types.
MPSTKZ Increases the size of the stacks used by threads executing in parallel
regions. The value should be an integer concatenated with M or
m to specify stack sizes of n megabytes.
MP_BIND Specifies whether to bind processes or threads executing in a
parallel region to a physical processor.
MP_BLIST When MP_BIND is yes, this variable specifically defines the threadCPU relationship, overriding the default values.
MP_SPIN Specifies the number of times to check a semaphore before calling
sched_yield() (on Linux) or _sleep() (on Windows).
MP_WARN Allows you to eliminate certain default warning messages.
NCPUS Sets the number of processes or threads used in parallel regions.
NCPUS_MAX Limits the maximum number of processors or threads that can be
used in a parallel region.PGI® User’s Guide
92
Environment Variable Description
NO_STOP_MESSAGE If used, the execution of a plain STOP statement does not produce
the message FORTRAN STOP.
OMP_DYNAMIC Currently has no effect. Enables (TRUE) or disables (FALSE) the
dynamic adjustment of the number of threads. The default is FALSE.
OMP_NESTED Currently has no effect. Enables (TRUE) or disables (FALSE)
nested parallelism. The default is FALSE.
OMP_NUM_THREADS Specifies the number of threads to use during execution of parallel
regions. Default is 1.
OMP_SCHEDULE Specifies the type of iteration scheduling and, optionally, the chunk
size to use for omp for and omp parallel for loops that include the
run-time schedule clause. The default is STATIC with chunk size = 1.
OMP_STACK_SIZE Overrides the default stack size for a newly created thread.
OMP_WAIT_POLICY Sets the behavior of idle threads, defining whether they spin or sleep
when idle. The values are ACTIVE and PASSIVE. The default is
ACTIVE.
PATH Determines which locations are searched for commands the user
may type.
PGI Specifies, at compile-time, the root directory where the PGI
compilers and tools are installed.
PGI_CONTINUE If set, when a program compiled with–Mchkfpstk is executed, the
stack is automatically cleaned up and execution then continues.
PGI_OBJSUFFIX Allows you to control the suffix on generated object files.
PGI_STACK_USAGE (Windows only) Allows you to explicitly set stack properties for your
program.
PGI_TERM Controls the stack traceback and just-in-time debugging
functionality.
PGI_TERM_DEBUG Overrides the default behavior when PGI_TERM is set to debug.
PWD Allows you to display the current directory.
STATIC_RANDOM_SEED Forces the seed returned by RANDOM_SEED to be constant.
TMP Sets the directory to use for temporary files created during execution
of the PGI compilers and tools; interchangeable with TMPDIR.
TMPDIR Sets the directory to use for temporary files created during execution
of the PGI compilers and tools.
PGI Environment Variables
You use the environment variables listed in Table 8.1, “PGI-related Environment Variable Summary Table” to
alter the default behavior of the PGI compilers and the executables which they generate. This section provides
more detailed descriptions about the variables in this table that are not OpenMP environment variables.Chapter 8. Using Environment Variables
93
FLEXLM_BATCH
By default, on Windows the license server creates interactive pop-up messages to issue warning and errors.
You can use the environment variable FLEXLM_BATCH to prevent interactive pop-up windows. To do this, set
the environment variable FLEXLM_BATCH to 1.
The following csh example prevents interactive pop-up messages for licensing warnings and errors:
% set FLEXLM_BATCH = 1;
FORTRAN_OPT
FORTRAN_OPT allows the user to specify that the PGI Fortran compilers user VAX I/O conventions.
• If FORTRAN_OPT exists and contains the value vaxio, the record length in the open statement is in units
of 4-byte words, and the $ edit descriptor only has an effect for lines beginning with a space or a plus sign
(+).
• If this variable exists and contains the value format_relaxed, an I/O item corresponding to a numerical
edit descriptor (such as F, E, I, and so on) is not required to be a type implied by the descriptor.
The following example causes the PGI Fortran compilers to use VAX I/O conventions:
$ setenv FORTRAN_OPT vaxio
GMON_OUT_PREFIX
GMON_OUT_PREFIX specifies the name of the output file for programs that are compiled and linked with the
-pg option. The default name is gmon.out.a.
If GMON_OUT_PREFIX is set, the name of the output file has GMON_OUT_PREFIX as a prefix.
Further, the suffix is the pid of the running process. The prefix and suffix are separated by a dot.
For example, if the output file is mygmon, then the full filename may look something similar to this:
GMON_OUT_PREFIX.mygmon.0012348567.
The following example causes the PGI Fortran compilers to use pgout as the output file for programs
compiled and linked with the -pg option.
$ setenv GMON_OUT_PREFIX pgout
LD_LIBRARY_PATH
The LD_LIBRARY_PATH variable is a colon-separated set of directories specifying where libraries should
first be searched, prior to searching the standard set of directories. This variable is useful when debugging a
new library or using a nonstandard library for special purposes.
The following csh example adds the current directory to your LD_LIBRARY_PATH variable.
% setenv LD_LIBRARY_PATH "$LD_LIBRARY_PATH":"./"
LM_LICENSE_FILE
The LM_LICENSE_FILE variable specifies the full path of the license file that is required for running the PGI
software.PGI® User’s Guide
94
For example, once the license file is in place, you can execute the following csh commands to make the
products you have purchased accessible and to initialize your environment for use of FLEXlm. These
commands assume that you use the default installation directory: /opt/pgi
% setenv PGI /opt/pgi
% setenv LM_LICENSE_FILE "$LM_LICENSE_FILE":/opt/pgi/license.dat
To set the environment variable LM_LICENSE_FILE to the full path of the license key file, do this:
1. Open the System Properties dialog: Start | Control Panel | System.
2. Select the Advanced tab.
3. Click the Environment Variables button.
• If LM_LICENSE_FILE is not already an environment variable, create a new system variable for it. Set
its value to the full path, including the name of the file, for the license key file, license.dat.
• If LM_LICENSE_FILE already exists as an environment variable, append the path to the license file to
the variable’s current value using a semi-colon to separate entrie
• If LM_LICENSE_FILE is not already an environment variable, create a new system variable for it. Set its
value to the full path, including the name of the file, for the license key file, license.dat.
• If LM_LICENSE_FILE already exists as an environment variable, append the path to the license file to the
variable’s current value using a semi-colon to separate entrie
MANPATH
The MANPATH variable sets the directories that are searched for manual pages associated with the commands
that the user types. When using PGI products, it is important that you set your PATH to include the location of
the PGI products and then set the MANPATH variable to include the man pages associated with the products.
The following csh example targets x64 linux86-64 version of the compilers and tool s and allows the user
access to the manual pages associated with them.
% set path = (/opt/pgi/linux86-64/7.1/bin $path
% setenv MANPATH "$MANPATH":/opt/pgi/linux86-64/7.1/man
MPSTKZ
MPSTKZ increases the size of the stacks used by threads executing in parallel regions. You typically use this
variable with programs that utilize large amounts of thread-local storage in the form of private variables or
local variables in functions or subroutines called within parallel regions. The value should be an integer
concatenated with M or m to specify stack sizes of n megabytes.
For example, the following setting specifies a stack size of 8 megabytes.
$ setenv MPSTKZ 8M
MP_BIND
You can set MP_BIND to yes or y to bind processes or threads executing in a parallel region to physical
processor. Set it to no or n to disable such binding. The default is to not bind processes to processors. ThisChapter 8. Using Environment Variables
95
variable is an execution-time environment variable interpreted by the PGI runtime-support libraries. It does
not affect the behavior of the PGI compilers in any way.
Note
The MP_BIND environment variable is not supported on all platforms.
$ setenv MP_BIND y
MP_BLIST
MP_BLIST allows you to specifically define the thread-CPU relationship.
Note
This variable is only in effect when MP_BIND is yes .
While the MP_BIND variable binds processors or threads to a physical processor, MP_BLIST allows you to
specifically define which thread is associated with which processor. The list defines the processor-thread
relationship order, beginning with thread 0. This list overrides the default binding.
For example, the following setting for MP_BLIST maps CPUs 3, 2, 1 and 0 to threads 0, 1, 2 and 3 respectively.
$ setenv MP_BLIST=3,2,1,0
MP_SPIN
When a thread executing in a parallel region enters a barrier, it spins on a semaphore. You can use MP_SPIN
to specify the number of times it checks the semaphore before calling sched_yield() (on Linux) or
_sleep() (on Windows). These calls cause the thread to be re-scheduled, allowing other processes to run.
The default values are 100 (on Linux) and 10000 (on Windows).
$ setenv MP_SPIN 200
MP_WARN
MP_WARN allows you to eliminate certain default warning messages.
By default, a warning is printed to stderr if you execute an OpenMP or auto-parallelized program with NCPUS
or OMP_NUM_THREADS set to a value larger than the number of physical processors in the system.
For example, if you produce a parallelized executable a.out and execute as follows on a system with only one
processor:
% setenv OMP_NUM_THREADS 2
% a.out
Warning: OMP_NUM_THREADS or NCPUS (2) greater
than available cpus (1)
FORTRAN STOP
Setting MP_WARN to NO eliminates these warning messages.PGI® User’s Guide
96
NCPUS
You can use the NCPUS environment variable to set the number of processes or threads used in parallel
regions. The default is to use only one process or thread, which is known as serial mode.
Note
OMP_NUM_THREADS has the same functionality as NCPUS. For historical reasons, PGi supports
the environment variable NCPUS. If both OMP_NUM_THREADS and NCPUS are set, the value of
OMP_NUM_THREADS takes precedence.
Warning
Setting NCPUS to a value larger than the number of physical processors or cores in your system can
cause parallel programs to run very slowly.
NCPUS_MAX
You can use the NCPUS_MAX environment variable to limit the maximum number of processes or threads
used in a parallel program. Attempts to dynamically set the number of processes or threads to a higher value,
for example using set_omp_num_threads(), will cause the number of processes or threads to be set at the
value of NCPUS_MAX rather than the value specified in the function call.
NO_STOP_MESSAGE
If the NO_STOP_MESSAGE variable exists, the execution of a plain STOP statement does not produce the
message FORTRAN STOP. The default behavior of the PGI Fortran compilers is to issue this message.
PATH
The PATH variable sets the directories that are searched for commands that the user types. When using PGI
products, it is important that you set your PATH to include the location of the PGI products.
You can also use this variable to specify that you want to use only the linux86 version of the compilers and
tools, or to target linux86 as the default.
The following csh example targets x64 linux86-64 version of the compilers and tools.
% set path = (/opt/pgi/linux86-64/7.1/bin $path)
PGI
The PGI environment variable specifies the root directory where the PGI compilers and tools are installed.
This variable is recognized at compile-time. If it is not set, the default value depends on your system as well as
which compilers are installed:
• On Linux, the default value of this variable is /opt/pgi.
• On Windows, the default value is C:\Program Files\PGI, where C represents the system drive. If both
32- and 64-bit compilers are installed, the 32-bit compilers are inC:\Program Files (x86)\ PGIChapter 8. Using Environment Variables
97
• For SFU/SUA compilers, the default value of this variable is /opt/pgi in the SFU/SUA file system. The
corresponding Windows-style path is C:/SFU/opt/pgi for SFU and C:/WINDOWS/SUA/opt/pgi for
SUA, where C represents the system drive.
In most cases, if the PGI environment variable is not set, the PGI compilers and tools dynamically determine
the location of this root directory based on the instance of the compiler or tool that was invoked. However,
there are still some dependencies on the PGI environment variable, and it can be used as a convenience when
initializing your environment for use of the PGI compilers and tools.
For example, assuming you use csh and want the 64-bit linux86-64 versions of the PGI compilers and tools to
be the default, you would use this syntax:
% setenv PGI /usr/pgi
% setenv MANPATH "$MANPATH":$PGI/linux86/6.0/man
% setenv LM_LICENSE_FILE $PGI/license.dat
% set path = ($PGI/linux86-64/6.0/bin $path)
PGI_CONTINUE
You set the PGI_CONTINUE variable to specify the actions to take before continuing with execution. For
example, if the PGI_CONTINUE environment variable is set and a program compiled with –Mchkfpstk
is executed, the stack is automatically cleaned up and execution then continues. If PGI_CONTINUE is set to
verbose, the stack is automatically cleaned up, a warning message is printed, and then execution continues.
Note
There is a performance penalty associated with the stack cleanup.
PGI_OBJSUFFIX
You can set the PGI_OBJSUFFIX environment variable to generate object files that have a specific suffix. For
example, if you set PGI_OBJSUFFIX to .o, the object files have a suffix of .o rather than .obj.
PGI_STACK_USAGE
(Windows only) The PGI_STACK_USAGE variable (for Windows only) allows you to explicitly set stack
properties for your program. When the user compiles a program with the –Mchkstk option and sets the
PGI_STACK_USAGE environment variable to any value, the program displays the stack space allocated and used
after the program exits. You might see something similar to the following message:
thread 0 stack: max 8180KB, used 48KB
This message indicates that the program used 48KB of a 8180KB allocated stack. For more information on the
–Mchkstk option, refer to –Mchkstk.
PGI_TERM
The PGI_TERM environment variable controls the stack traceback and just-in-time debugging functionality.
The runtime libraries use the value of ‘ to determine what action to take when a program abnormally
terminates.PGI® User’s Guide
98
The value of PGI_TERM is a comma-separated list of options. The commands for setting the environment
variable follow.
• In csh:
% setenv PGI_TERM option[,option...]
• In bash or sh:
$ PGI_TERM=option[,option...]
$ export PGI_TERM
• In the Windows Command Prompt:
C:\> set PGI_TERM=option[,option...]
Table 8.2 lists the supported values for option. Following the table is a complete description of each option
that indicates specifically how you might apply the option.
By default, all of these options are disabled.
Table 8.2. Supported PGI_TERM Values
[no]debug Enables/disables just-in-time debugging (debugging invoked on error)
[no]trace Enables/disables stack traceback on error
[no]signal Enables/disables establishment of signal handlers for common signals
that cause program termination
[no]abort Enables/disables calling the system termination routine abort()
[no]debug
This enables/disables just-in-time debugging. The default is nodebug.
When PGI_TERM is set to debug, the following command is invoked on error, unless you use
PGI_TERM_DEBUG to override this default.
pgdbg -text -attach
is the process ID of the process being debugged.
The PGI_TERM_DEBUG environment variable may be set to override the default setting. For more information,
refer to “PGI_TERM_DEBUG,” on page 99.
[no]trace
This enables/disables the stack traceback. The default is notrace.
[no]signal
This enables/disables the establishing signal handlers for the most common signals that cause program
termination. The default is nosignal. You can set trace and debug automatically enables signal.
Specifically setting nosignal allows you to override this behavior.Chapter 8. Using Environment Variables
99
[no]abort
This enables/disables calling the system termination routine abort(). The default is noabort. When
noabort is in effect the process terminates by calling _exit(127).
On Linux and SUA, when abort is in effect, the abort routine creates a core file and exits with code 127.
On Windows, when abort is in effect, the abort routine exits with the status of the exception received. For
example, if the program receives an access violation, abort() exits with status 0xC0000005.
A few runtime errors just print an error message and call exit(127), regardless of the status of PGI_TERM.
These are mainly errors such as specifying an invalid environment variable value where a traceback would not
be useful.
If it appears that abort() does not generate core files on a Linux system, be sure to unlimit the coredumpsize.
You can do this in these ways:
• Using csh:
% limit coredumpsize unlimited
% setenv PGI_TERM abort
• Using bash or sh:
$ ulimit -c unlimited
$ export PGI_TERM=abort
To debug a core file with pgdbg, start pgdbg with the -core option. For example, to view a core file named
“core” for a program named “a.out”:
$ pgdbg -core core a.out
For more information on why to use this variable, refer to “Stack Traceback and JIT Debugging,” on page
101.
PGI_TERM_DEBUG
The PGI_TERM_DEBUG variable may be set to override the default behavior when PGI_TERM is set to debug.
The value of PGI_TERM_DEBUG should be set to the command line used to invoke the program. For example:
gdb --quiet --pid %d
The first occurrence of %d in the PGI_TERM_DEBUG string will be replaced by the process id. The program
named in the PGI_TERM_DEBUG string must be found on the currentPATH or specified with a full path name.
PWD
The PWD variable allows you to display the current directory.
STATIC_RANDOM_SEED
You can use STATIC_RANDOM_SEED to force the seed returned by the Fortran 90/95 RANDOM_SEED
intrinsic to be constant. The first call to RANDOM_SEED without arguments resets the random seed to aPGI® User’s Guide
100
default value, then advances the seed by a variable amount based on time. Subsequent calls to RANDOM_SEED
without arguments reset the random seed to the same initial value as the first call. Unless the time is exactly the
same, each time a program is run a different random number sequence is generated. Setting the environment
variable STATIC_RANDOM_SEED to YES forces the seed returned by RANDOM_SEED to be constant, thereby
generating the same sequence of random numbers at each execution of the program.
TMP
You can use TMP to specify the directory to use for placement of any temporary files created during execution
of the PGI compilers and tools. This variable is interchangeable with TMPDIR.
TMPDIR
You can use TMPDIR to specify the directory to use for placement of any temporary files created during
execution of the PGI compilers and tools.
Using Environment Modules
On Linux, if you use the Environment Modules package, that is, the module load command, PGI 7.1
includes a script to set up the appropriate module files.
Assuming your installation base directory is /opt/pgi, and your MODULEPATH environment variable is /
usr/local/Modules/modulefiles, execute this command:
% /opt/pgi/linux86/7.1-1/etc/modulefiles/pgi.module.install \
-all -install /usr/local/Modules/modulefiles
This command creates module files for all installed versions of the PGI compilers. You must have write
permission to the modulefiles directory to enable the module commands:
% module load pgi32/7.1
% module load pgi64/7.1
% module load pgi/7.1
where "pgi/7.1" uses the 32-bit compilers on a 32-bit system and uses 64-bit compilers on a 64-bit system.
To see what versions are available, use this command:
% module avail pgi
The module load command sets or modifies the environment variables as indicated in the following table.
This Environment Variable... Is set or modified to ...
CC Full path to pgcc
V Path to pgCC
V Full path to pgCC
CXX Path to pgCC
FC Full path to pgf95
F77 Full path to pgf77Chapter 8. Using Environment Variables
101
This Environment Variable... Is set or modified to ...
F90 Full path to pgf95
LD_LIBRARY_PATH Prepends the PGI library directory
MANPATH Prepends the PGI man page directory
PATH Prepends the PGI compiler and tools bin directory
PGI The base installation directory
PGI does not provide support for the Environment Modules package. For more information about the package,
go to: modules.sourceforge.net.
Stack Traceback and JIT Debugging
When a programming error results in a run-time error message or an application exception, a program will
usually exit, perhaps with an error message. The PGI run-time library includes a mechanism to override this
default action and instead print a stack traceback, start a debugger, or (on Linux) create a core file for postmortem debugging.
The stack traceback and just-in-time debugging functionality is controlled by an environment variable,
PGI_TERM. The run-time libraries use the value of PGI_TERM to determine what action to take when a
program abnormally terminates.
When the PGI runtime library detects an error or catches a signal, it calls the routine pgi_stop_here()
prior to generating a stack traceback or starting the debugger. The pgi_stop_here routine is a convenient spot
to set a breakpoint when debugging a program.
For more information on PGI_Term and the supported values, refer to “PGI_TERM,” on page 97.102103
Chapter 9. Distributing Files -
Deployment
Once you have successfully built, debugged and tuned your application, you may want to distribute it to users
who need to run it on a variety of systems. This chapter addresses how to effectively distribute applications
built using PGI compilers and tools. The application must be installed in such a way that the it executes
accurately on a system other than the one on which it was built, and which may be configured differently.
Deploying Applications on Linux
To successfully deploy your application on Linux, there are a number of issues to consider, including these:
• Runtime Libraries
• 64-bit Linux Systems
• Redistribution of Files
• Linux Portability of files and packages
• Licensing
Runtime Library Considerations
On Linux systems, the system runtime libraries can be linked to an application either statically, or dynamically,
For example, for the C runtime library, libc, you can use either the static version libc.a or the shared object
libc.so. If the application is intended to run on Linux systems other than the one on which it was built, it is
generally safer to use the shared object version of the library. This approach ensures that the application uses
a version of the library that is compatible with the system on which the application is running. Further, it works
best when the application is linked on a system that has an equivalent or earlier version of the system software
than the system on which the application will be run.
Note
Building on a newer system and running the application on an older system may not produce the
desired output.PGI® User’s Guide
104
To use the shared object version of a library, the application must also link to shared object versions of the
PGI runtime libraries. To execute an application built in such a way on a system on which PGI compilers are
not installed, those shared objects must be available.To build using the shared object versions of the runtime
libraries, use the -Bdynamic option, as shown here:
$ pgf90 -Bdynamic myprog.f90
64-bit Linux Considerations
On 64-bit Linux systems, 64-bit applications that use the -mcmodel=medium option sometimes cannot be
successfully linked statically. Therefore, users with executables built with the -mcmodel=medium option may
need to use shared libraries, linking dynamically. Also, runtime libraries built using the -fpic option use
32-bit offsets, so they sometimes need to reside near other runtime libs in a shared area of Linux program
memory.
Note
If your application is linked dynamically using shared objects, then the shared object versions of the
PGI runtime are required.
Linux Redistributable Files
There are two methods for installing the shared object versions of the runtime libraries required for
applications built with PGI compilers and tools: Linux Portability Package and manual distribution.
PGI provides the Linux Portability Package, an installation package that can be downloaded from the PGI web
site. In addition, when the PGI compilers are installed, there is a directory named REDIST for each platform
(linux86 and linux86-64) that contains the redistributed shared object libraries. These may be redistributed by
licensed PGI customers under the terms of the PGI End-User License Agreement.
Restrictions on Linux Portability
You cannot expect to be able to run an executable on any given Linux machine. Portability depends on the
system you build on as well as how much your program uses system routines that may have changed from
Linux release to Linux release. For example, one area of significant change between some versions of Linux is
in libpthread.so. PGI compilers use this shared object for the options -Mconcur (auto-parallel) and -
mp (OpenMP) programs.
Typically, portability is supported for forward execution, meaning running a program on the same or a later
version of Linux; but not for backward compatibility, that is, running on a prior release. For example, a user
who compiles and links a program under Suse 9.1 should not expect the program to run without incident on
a Red Hat 8.0 system, which is an earlier version of Linux. It may run, but it is less likely. Developers might
consider building applications on earlier Linux versions for wider usage.
Installing the Linux Portability Package
You can download the Linux Portability Packages from the Downloads page at http://www.pgroup.com. First
download the package you need, then untar it, and run the install script. Then you can add the installation
directory to your library path.Chapter 9. Distributing Files - Deployment
105
To use the installed libraries, you can either modify /etc/ld.so.conf and run ldconfig(1) or modify
the environment variable LD_LIBRARY_PATH, as shown here:
setenv LD_LIBRARY_PATH /usr/local/pgi
or
export LD_LIBRARY_PATH=/usr/local/pgi
Licensing for Redistributable Files
The installation of the Linux Portability Package presents the standard PGI usage license. The libs can be
distributed for use with PGI compiled applications, within the provisions of that license.
The files in the REDIST directories may be redistributed under the terms of the End-User License Agreement
for the product in which they were included.
Deploying Applications on Windows
Windows programs may be linked statically or dynamically.
• A statically linked program is completely self-contained, created by linking to static versions of the PGI and
Microsoft runtime libraries.
• A dynamically linked program depends on separate dynamically-linked libraries (DLLs) that must be
installed on a system for the application to run on that system.
Although it may be simpler to install a statically linked executable, there are advantages to using the DLL
versions of the runtime, including these:
• Executable binary file size is smaller.
• Multiple processes can use DLLs at once, saving system resources.
• New versions of the runtime can be installed and used by the application without rebuilding the application.
Dynamically-linked Windows programs built with PGI compilers depend on dynamic run-time library files
(DLLs). These DLLs must be distributed with such programs to enable them to execute on systems where
the PGI compilers are not installed. These redistributable libraries include both PGI runtime libraries and
Microsoft runtime libraries.
PGI Redistributables
PGI Redistributable directories contain all of the PGI Linux runtime library shared object files or Windows
dynamically- linked libraries that can be re-distributed by PGI 7.1 licensees under the terms of the PGI Enduser License Agreement (EULA).
Microsoft Redistributables
The PGI products on Windows include Microsoft Open Tools. The Microsoft Open Tools directory contains a
subdirectory named redist. PGI licensees may redistribute the files contained in this directory in accordance
with the terms of the PGI End-User License Agreement.PGI® User’s Guide
106
Microsoft supplies installation packages, vcredist_x86.exe and vcredist_x64.exe, containing these
runtime files. You can download these packages from www.microsoft.com.
Code Generation and Processor Architecture
The PGI compilers can generate much more efficient code if they know the specific x86 processor architecture
on which the program will run. When preparing to deploy your application, you should determine whether
you want the application to run on the widest possible set of x86 processors, or if you want to restrict the
application to run on a specific processor or set of processors. The restricted approach allows you to optimize
performance for that set of processors.
Different processors have differences, some subtle, in hardware features, such as instruction sets and cache
size. The compilers make architecture-specific decisions about such things as instruction selection, instruction
scheduling, and vectorization, all of which can have a profound effect on the performance of your application.
Processor- specific code generation is controlled by the -tp option, described in “–tp [,target...] ,”
on page 202. When an application is compiled without any -tp options, the compiler generates code for the
type of processor on which the compiler is run.
Generating Generic x86 Code
To generate generic x86 code, use one of the following forms of the-tp option on your command line:
-tp px ! generate code for any x86 cpu type
-tp p6 ! generate code for Pentium 2 or greater
While both of these examples are good choices for portable execution, most users have Pentium 2 or greater
CPUs.
Generating Code for a Specific Processor
You can use the -tp option to request that the compiler generate code optimized for a specific processor. The
PGI Release Notes contains a list of supported processors or you can look at the -tp entry in the compiler
output generated by using the -help option, described in “–help ,” on page 178.
Generating Code for Multiple Types of Processors in One Executable
PGI unified binaries provide a low-overhead method for a single program to run well on a number of
hardware platforms.
All 64-bit PGI compilers can produce PGI Unified Binary programs that contain code streams fully optimized
and supported for both AMD64 and Intel EM64T processors using the -tp target option.
The compilers generate and combine multiple binary code streams into one executable, where each stream
is optimized for a specific platform. At runtime, this one executable senses the environment and dynamically
selects the appropriate code stream.
Different processors have differences, some subtle, in hardware features, such as instruction sets and cache
size. The compilers make architecture-specific decisions about such things as instruction selection, instructionChapter 9. Distributing Files - Deployment
107
scheduling, and vectorization. PGI unified binaries provide a low-overhead means for a single program to run
well on a number of hardware platforms.
Executable size is automatically controlled via unified binary culling. Only those functions and subroutines
where the target affects the generated code will have unique binary images, resulting in a code-size savings of
10-90% compared to generating full copies of code for each target.
Programs can use PGI Unified Binary even if all of the object files and libraries are not compiled as unified
binaries. Like any other object file, you can use PGI Unified Binary object files to create programs or libraries.
No special start up code is needed; support is linked in from the PGI libraries.
The -Mpfi option disables generation of PGI Unified Binary. Instead, the default target auto-detect rules for
the host are used to select the target processor.
Unified Binary Command-line Switches
The PGI Unified Binary command-line switch is an extension of the target processor switch, -tp, which may
be applied to individual files during compilation .
The target processor switch, -tp, accepts a comma-separated list of 64-bit targets and generates code
optimized for each listed target.
The following example generates optimized code for three targets:
-tp k8-64,p7-64,core2-64
A special target switch, -tp x64, is the same as -tp k8-64, p7-64s.
Unified Binary Directives and Pragma
Unified binary directives and pragmas may be applied to functions, subroutines, or whole files. The directives
and pragmas cause the compiler to generate PGI Unified Binary code optimized for one or more targets. No
special command line options are needed for these pragmas and directives to take effect.
The syntax of the Fortran directive is this:
pgi$[g|r| ] pgi tp [target]...
where the scope is g (global), r (routine) or blank. The default is r, routine.
For example, the following syntax indicates that the whole file, represented by g, should be optimized for both
k8_64 and p7_64.
pgi$g pgi tp k8_64 p7_64
The syntax of the C/C++ pragma is this:
#pragma [global|routine|] tp [target]...
where the scope is global, routine, or blank. The default is routine.
For example, the following syntax indicates that the next function should be optimized for k8_64, p7_64, and
core2_64.
#pragma routine tp k8_64 p7_64 core2_64108109
Chapter 10. Inter-language Calling
This chapter describes inter-language calling conventions for C, C++, and Fortran programs using the PGI
compilers. The following sections describe how to call a Fortran function or subroutine from a C or C++
program and how to call a C or C++ function from a Fortran program. For information on calling assembly
language programs, refer to Chapter 18, “Run-time Environment”.
This chapter provides examples that use the following options related to inter-language calling. For more
information on these options, refer to Chapter 15, “Command-Line Options Reference,” on page 163.
-c -Mnomain
Overview of Calling Conventions
This chapter includes information on the following topics:
• Functions and subroutines in Fortran, C, and C++
• Naming and case conversion conventions
• Compatible data types
• Argument passing and special return values
• Arrays and indexes
• Win32 calling conventions
The sections “Inter-language Calling Considerations,” on page 110 through“Example - C++ Calling Fortran,”
on page 119 describe how to perform inter-language calling using the Linux/Win64/SUA convention.
Default Fortran calling conventions for Win32 differ, although Win32 programs compiled using the -Munix
Fortran command-line option use the Linux/Win64 convention rather than the default Win32 conventions. All
information in those sections pertaining to compatibility of arguments applies to Win32 as well. For details
on the symbol name and argument passing conventions used on Win32 platforms, refer to “Win32 Calling
Conventions,” on page 120.PGI® User’s Guide
110
Inter-language Calling Considerations
In general, when argument data types and function return values agree, you can call a C or C++ function from
Fortran as well as call a Fortran function from C or C++. When data types for arguments do not agree, you may
need to develop custom mechanisms to handle them. For example, the Fortran COMPLEX type has a matching
type in C99 but does not have a matching type in C90; however, it is still possible to provide inter-language
calls but there are no general calling conventions for such cases.
Note
• If a C++ function contains objects with constructors and destructors, calling such a function from
either C or Fortran is not possible unless the initialization in the main program is performed from a
C++ program in which constructors and destructors are properly initialized.
• In general, you can call a C or Fortran function from C++ without problems as long as you use the
extern "C" keyword to declare the function in the C++ program. This declaration prevents name
mangling for the C function name. If you want to call a C++ function from C or Fortran, you also
have to use the extern "C" keyword to declare the C++ function. This keeps the C++ compiler
from mangling the name of the function.
• You can use the __cplusplus macro to allow a program or header file to work for both C and C++.
For example, the following defines in the header file stdio.h allow this file to work for both C and
C++.
#ifndef _STDIO_H
#define _STDIO_H
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
.
. /* Functions and data types defined... */
.
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif
• C++ member functions cannot be declared extern, since their names will always be mangled.
Therefore, C++ member functions cannot be called from C or Fortran.
Functions and Subroutines
Fortran, C, and C++ define functions and subroutines differently.
For a Fortran program calling a C or C++ function, observe the following return value convention:
• When a C or C++ function returns a value, call it from Fortran as a function.
• When a C or C++ function does not return a value, call it as a subroutine.
For a C/C++ program calling a Fortran function, the call should return a similar type. Table 10.1, “Fortran and
C/C++ Data Type Compatibility,” on page 111 lists compatible types. If the call is to a Fortran subroutine,Chapter 10. Inter-language Calling
111
a Fortran CHARACTER function, or a Fortran COMPLEX function, call it from C/C++ as a function that
returns void. The exception to this convention is when a Fortran subroutine has alternate returns; call such
a subroutine from C/C++ as a function returning int whose value is the value of the integer expression
specified in the alternate RETURN statement.
Upper and Lower Case Conventions, Underscores
By default on Linux, Win64, OSX, and SUA systems, all Fortran symbol names are converted to lower case.
C and C++ are case sensitive, so upper-case function names stay upper-case. When you use inter-language
calling, you can either name your C/C++ functions with lower-case names, or invoke the Fortran compiler
command with the option –Mupcase, in which case it will not convert symbol names to lower-case.
When programs are compiled using one of the PGI Fortran compilers on Linux, Win64, OSX, and SUA systems,
an underscore is appended to Fortran global names (names of functions, subroutines and common blocks).
This mechanism distinguishes Fortran name space from C/C++ name space. Use these naming conventions:
• If you call a C/C++ function from Fortran, you should rename the C/C++ function by appending an
underscore or use C$PRAGMA C in the Fortran program. For more information on C$PRAGMA C, refer to
“C$PRAGMA C,” on page 72.
• If you call a Fortran function from C/C++, you should append an underscore to the Fortran function name
in the calling program.
Compatible Data Types
Table 10.1 shows compatible data types between Fortran and C/C++. Table 10.2, “Fortran and C/C++
Representation of the COMPLEX Type,” on page 112 shows how the Fortran COMPLEX type may be
represented in C/C++. If you can make your function/subroutine parameters as well as your return values
match types, you should be able to use inter-language calling.
Table 10.1. Fortran and C/C++ Data Type Compatibility
Fortran Type (lower case) C/C++ Type Size (bytes)
character x char x 1
character*n x char x[n] n
real x float x 4
real*4 x float x 4
real*8 x double x 8
double precision double x 8
integer x int x 4
integer*1 x signed char x 1
integer*2 x short x 2
integer*4 x int x 4
integer*8 x long long x 8PGI® User’s Guide
112
Fortran Type (lower case) C/C++ Type Size (bytes)
logical x int x 4
logical*1 x char x 1
logical*2 x short x 2
logical*4 int x 4
logical*8 long long x 8
Table 10.2. Fortran and C/C++ Representation of the COMPLEX Type
Fortran Type (lower case) C/C++ Type Size (bytes)
complex x struct {float r,i;} x; 8
float complex x;
complex*8 x struct {float r,i;} x; 8
float complex x; 8
double complex x struct {double dr,di;} x; 16
double complex x; 16
complex *16 x struct {double dr,di;} x; 16
double complex x; 16
Note
For C/C++, the complex type implies C99 or later.
Fortran Named Common Blocks
A named Fortran common block can be represented in C/C++ by a structure whose members correspond to
the members of the common block. The name of the structure in C/C++ must have the added underscore. For
example, the Fortran common block:
INTEGER I
COMPLEX C
DOUBLE COMPLEX CD
DOUBLE PRECISION D
COMMON /COM/ i, c, cd, d
is represented in C with the following equivalent:
extern struct {
int i;
struct {float real, imag;} c;
struct {double real, imag;} cd;
double d;
} com_;
and in C++ with the following equivalent:Chapter 10. Inter-language Calling
113
extern "C" struct {
int i;
struct {float real, imag;} c;
struct {double real, imag;} cd;
double d;
} com_;
Tip
For global or external data sharing, extern “C” is not required.
Argument Passing and Return Values
In Fortran, arguments are passed by reference, that is, the address of the argument is passed, rather than the
argument itself. In C/C++, arguments are passed by value, except for strings and arrays, which are passed
by reference. Due to the flexibility provided in C/C++, you can work around these differences. Solving the
parameter passing differences generally involves intelligent use of the & and * operators in argument passing
when C/C++ calls Fortran and in argument declarations when Fortran calls C/C++.
For strings declared in Fortran as type CHARACTER, an argument representing the length of the string is also
passed to a calling function.
On Linux systems, or when using the UNIX calling convention on Windows (-Munix), the compiler places
the length argument(s) at the end of the parameter list, following the other formal arguments. The length
argument is passed by value, not by reference.
Passing by Value (%VAL)
When passing parameters from a Fortran subprogram to a C/C++ function, it is possible to pass by value using
the %VAL function. If you enclose a Fortran parameter with %VAL(), the parameter is passed by value. For
example, the following call passes the integer i and the logical bvar by value.
integer*1 i
logical*1 bvar
call cvalue (%VAL(i), %VAL(bvar))
Character Return Values
“Functions and Subroutines,” on page 110 describes the general rules for return values for C/C++ and
Fortran inter-language calling. There is a special return value to consider. When a Fortran function returns a
character, two arguments need to be added at the beginning of the C/C++ calling function’s argument list:
• The address of the return character or characters
• The length of the return character
Example 10.1, “Character Return Parameters” illustrates the extra parameters, tmp and 10, supplied by the
caller:PGI® User’s Guide
114
Example 10.1. Character Return Parameters
! Fortran function returns a character
CHARACTER*(*) FUNCTION CHF( C1,I)
CHARACTER*(*) C1
INTEGER I
END
/* C declaration of Fortran function */
extern void chf_();
char tmp[10];
char c1[9];
int i;
chf_(tmp, 10, c1, &i, 9);
If the Fortran function is declared to return a character value of constant length, for example CHARACTER*4
FUNCTION CHF(), the second extra parameter representing the length must still be supplied, but is not
used.
NOTE
The value of the character function is not automatically NULL-terminated.
Complex Return Values
When a Fortran function returns a complex value, an argument needs to be added at the beginning of the C/
C++ calling function’s argument list; this argument is the address of the complex return value. Example 10.2,
“COMPLEX Return Values” illustrates the extra parameter, cplx, supplied by the caller.
Example 10.2. COMPLEX Return Values
COMPLEX FUNCTION CF(C, I)
INTEGER I
. . .
END
extern void cf_();
typedef struct {float real, imag;} cplx;
cplx c1;
int i;
cf_(&c1, &i);
Array Indices
C/C++ arrays and Fortran arrays use different default initial array index values. By default, C/C++ arrays start
at 0 and Fortran arrays start at 1. If you adjust your array comparisons so that a Fortran second element is
compared to a C/C++ first element, and adjust similarly for other elements, you should not have problems
working with this difference. If this is not satisfactory, you can declare your Fortran arrays to start at zero.
Another difference between Fortran and C/C++ arrays is the storage method used. Fortran uses columnmajor order and C/C++ use row-major order. For one-dimensional arrays, this poses no problems. For twodimensional arrays, where there are an equal number of rows and columns, row and column indexes can
simply be reversed. For arrays other than single dimensional arrays, and square two-dimensional arrays, interlanguage function mixing is not recommended.Chapter 10. Inter-language Calling
115
Examples
This section contains examples that illustrate inter-language calling.
Example - Fortran Calling C
Example 10.4, “C function cfunc_” shows a C function that is called by the Fortran main program shown
in Example 10.3, “Fortran Main Program fmain.f”. Notice that each argument is defined as a pointer, since
Fortran passes by reference. Also notice that the C function name uses all lower-case and a trailing "_".
Example 10.3. Fortran Main Program fmain.f
logical*1 bool1
character letter1
integer*4 numint1, numint2
real numfloat1
double precision numdoub1
integer*2 numshor1
external cfunc
call cfunc (bool1, letter1, numint1, numint2,
+ numfloat1, numdoub1, numshor1)
write( *, "(L2, A2, I5, I5, F6.1, F6.1, I5)")
+ bool1, letter1, numint1, numint2, numfloat1,
+ numdoub1, numshor1
end
Example 10.4. C function cfunc_
#define TRUE 0xff
#define FALSE 0
void cfunc_( bool1, letter1, numint1, numint2, numfloat1,\
numdoub1, numshor1, len_letter1)
char *bool1, *letter1;
int *numint1, *numint2;
float *numfloat1;
double *numdoub1;
short *numshor1;
int len_letter1;
{
*bool1 = TRUE; *letter1 = 'v'; *numint1 = 11; *numint2 = -44;
*numfloat1 = 39.6 ; *numdoub1 = 39.2; *numshor1 = 981;
}
Compile and execute the program fmain.f with the call to cfunc_ using the following command lines:
$ pgcc -c cfunc.c
$ pgf95 cfunc.o fmain.f
Executing the a.out file should produce the following output:
T v 11 -44 39.6 39.2 981
Example - C Calling Fortran
Example 10.6, “C Main Program cmain.c” shows a C main program that calls the Fortran subroutine shown in
Example 10.5, “Fortran Subroutine forts.f”. Notice that each call uses the & operator to pass by reference. Also
notice that the call to the Fortran subroutine uses all lower-case and a trailing "_".PGI® User’s Guide
116
Example 10.5. Fortran Subroutine forts.f
subroutine forts ( bool1, letter1, numint1
+ numint2, numfloat1, numdoub1, numshor1)
logical*1 bool1
character letter1
integer numint1, numint2
double precision numdoub1
real numfloat1
integer*2 numshor1
bool1 = .true.
letter1 = "v"
numint1 = 11
numint2 = -44
numdoub1 = 902
numfloat1 = 39.6
numshor1 = 299
return
end
Example 10.6. C Main Program cmain.c
main () {
char bool1, letter1;
int numint1, numint2;
float numfloat1;
double numdoub1;
short numshor1;
extern void forts_ ();
forts_(&bool1,&letter1,&numint1,&numint2,&numfloat1,&numdoub1,&numshor1, 1);
printf(" %s %c %d %d %3.1f %.0f %d\n",
bool1?"TRUE":"FALSE",letter1,numint1,
numint2, numfloat1, numdoub1, numshor1);
}
To compile this Fortran subroutine and C program, use the following commands:
$ pgcc -c cmain.f
$ pgf95 -Mnomain cmain.o forts.f
Executing the resulting a.out file should produce the following output:
TRUE v 11 -44 39.6 902 299
Example - C ++ Calling C
Example 10.8, “C++ Main Program cpmain.C Calling a C Function” shows a C++ main program that calls the
C function shown in Example 10.7, “Simple C Function cfunc.c”.
Example 10.7. Simple C Function cfunc.c
void cfunc(num1, num2, res)
int num1, num2, *res;
{
printf("func: a = %d b = %d ptr c = %x\n",num1,num2,res);
*res=num1/num2;
printf("func: res = %d\n",*res);
}Chapter 10. Inter-language Calling
117
Example 10.8. C++ Main Program cpmain.C Calling a C Function
xtern "C" void cfunc(int n, int m, int *p);
#include
main()
{
int a,b,c;
a=8;
b=2;
cout << "main: a = "<
extern "C" { extern void forts_(char *,char *,int *,int *,
float *,double *,short *); }
main ()
{
char bool1, letter1;
int numint1, numint2;
float numfloat1;
double numdoub1;
short numshor1;
forts_(&bool1,&letter1,&numint1,&numint2,&numfloat1,
&numdoub1,&numshor1);
cout << " bool1 = ";
bool1?cout << "TRUE ":cout << "FALSE "; cout < 2GB in
size. Note that if you execute with the above settings in your environment, you may see the following:
% bigadd
Segmentation fault
Execution fails because the stack size is not large enough. Try resetting the stack size in your environment:
% limit stacksize 3000M PGI® User’s Guide
130
Note that ‘limit stacksize unlimited’ will probably not provide as large a stack as we are using above.
% bigadd
a[0]=1 b[0]=2 c[0]=3
n=599990000 a[599990000]=5.9999e+08 b[599990000]=1.19998e+09 c[599990000]=1.79997e+09
The size of the bss section of the bigadd executable is now larger than 2GB:
% size –-format=sysv bigadd | grep bss
.bss 4800000008 5245696
% size -–format=sysv bigadd | grep Total
Total 4800005080
Example: Medium Memory Model and Large Array in Fortran
The following example works with both the PGF95 and PGF77 compilers included in Release 7.0. Both
compilers use 64-bit addresses and index arithmetic when the –mcmodel=medium option is used.
Consider the following example:
% cat mat.f
program mat
integer i, j, k, size, l, m, n parameter (size=16000) ! >2GB
parameter (m=size,n=size)
real*8 a(m,n),b(m,n),c(m,n),d
do i = 1, m
do j = 1, n
a(i,j)=10000.0D0*dble(i)+dble(j)
b(i,j)=20000.0D0*dble(i)+dble(j)
enddo
enddo
!$omp parallel
!$omp do
do i = 1, m
do j = 1, n
c(i,j) = a(i,j) + b(i,j)
enddo
enddo
!$omp do
do i=1,m
do j = 1, n
d = 30000.0D0*dble(i)+dble(j)+dble(j)
if(d .ne. c(i,j)) then
print *,”err i=”,i,”j=”,j
print *,”c(i,j)=”,c(i,j)
print *,”d=”,d
stop
endif
enddo
enddo
!$omp end parallel
print *, “M =”,M,”, N =”,N
print *, “c(M,N) = “, c(m,n)
end
When compiled with the PGF95 compiler using –mcmodel=medium:
% pgf95 –mp –o mat mat.f –i8 –mcmodel=mediumChapter 11. Programming Considerations for 64-Bit Environments
131
% setenv OMP_NUM_THREADS 2
% mat
M = 16000 , N = 16000
c(M,N) = 480032000.0000000
Example: Large Array and Small Memory Model in Fortran
The following example uses large, dynamically-allocated arrays. The code is divided into a main and
subroutine so you could put the subroutine into a shared library. Dynamic allocation of large arrays saves
space in the size of executable and saves time initializing data. Further, the routines can be compiled with 32-
bit compilers, by just decreasing the parameter size below.
% cat mat_allo.f90
program mat_allo
integer i, j
integer size, m, n
parameter (size=16000)
parameter (m=size,n=size)
double precision, allocatable::a(:,:),b(:,:),c(:,:)
allocate(a(m,n), b(m,n), c(m,n))
do i = 100, m, 1
do j = 100, n, 1
a(i,j) = 10000.0D0 * dble(i) + dble(j)
b(i,j) = 20000.0D0 * dble(i) + dble(j)
enddo
enddo
call mat_add(a,b,c,m,n)
print *, “M =”,m,”,N =”,n
print *, “c(M,N) = “, c(m,n)
end
subroutine mat_add(a,b,c,m,n)
integer m, n, i, j
double precision a(m,n),b(m,n),c(m,n)
!$omp do
do i = 1, m
do j = 1, n
c(i,j) = a(i,j) + b(i,j)
enddo
enddo
return
end
% pgf95 –o mat_allo mat_allo.f90 –i8 –Mlarge_arrays -mp -fast132133
Chapter 12. C/C++ Inline Assembly
and Intrinsics
Inline Assembly
Inline Assembly lets you specify machine instructions inside a "C" function. The format for an inline assembly
instruction is this:
{ asm | __asm__ } ("string");
The asm statement begins with the asm or __asm__ keyword. The __asm__ keyword is typically used in
header files that may be included in ISO "C" programs.
"string" is one or more machine specific instructions separated with a semi-colon (;) or newline (\n)
character. These instructions are inserted directly into the compiler's assembly-language output for the
enclosing function.
Some simple asm statements are:
asm ("cli");
asm ("sti");
The asm statements above disable and enable system interrupts respectively.
In the following example, the eax register is set to zero.
asm( "pushl %eax\n\t" "movl $0, %eax\n\t" "popl %eax");
Notice that eax is pushed on the stack so that it is it not clobbered. When the statement is done with eax, it is
restored with the popl instruction.
Typically a program uses macros that enclose asm statements. The interrupt constructs shown above are used
in the following two examples:
#define disableInt __asm__ ("cli");
#define enableInt __asm__ ("sti");PGI® User’s Guide
134
Extended Inline Assembly
“Inline Assembly,” on page 133 explains how to use inline assembly to specify machine specific instructions
inside a "C" function. This approach works well for simple machine operations such as disabling and enabling
system interrupts. However, inline assembly has three distinct limitations:
1. The programmer must choose the registers required by the inline assembly.
2. To prevent register clobbering, the inline assembly must include push and pop code for registers that get
modified by the inline assembly.
3. There is no easy way to access stack variables in an inline assembly statement.
Extended Inline Assembly was created to address these limitations. The format for extended inline assembly,
also known as extended asm, is as follows:
{ asm | __asm__ } [ volatile | __volatile__ ]
("string" [: [output operands]] [: [input operands]] [: [clobberlist]]);
• Extended asm statements begin with the asm or __asm__ keyword. Typically the __asm__ keyword is
used in header files that may be included by ISO "C" programs.
• An optional volatile or __volatile__ keyword may appear after the asm keyword. This keyword instructs
the compiler not to delete, move significantly, or combine with any other asm statement. Like __asm__, the
__volatile__ keyword is typically used with header files that may be included by ISO "C" programs.
• "string" is one or more machine specific instructions separated with a semi-colon (;) or newline (\n)
character. The string can also contain operands specified in the [output operands], [input operands],
and [clobber list]. The instructions are inserted directly into the compiler's assembly-language output for
the enclosing function.
• The [output operands], [input operands], and [clobber list] items each describe the effect of the
instruction for the compiler. For example:
asm( "movl %1, %%eax\n" "movl %%eax, %0":"=r" (x) : "r" (y) : "%eax" );
where "=r" (x) is an output operand
"r" (y) is an input operand.
"%eax" is the clobber list consisting of one register, "%eax".
The notation for the output and input operands is a constraint string surrounded by quotes, followed by
an expression, and surrounded by parentheses. The constraint string describes how the input and output
operands are used in the asm "string". For example, "r" tells the compiler that the operand is a register.
The "=" tells the compiler that the operand is write only, which means that a value is stored in an output
operand's expression at the end of the asm statement.
Each operand is referenced in the asm "string" by a percent "%" and its number. The first operand is
number 0, the second is number 1, the third is number 2, and so on. In the preceding example, "%0"
references the output operand, and "%1" references the input operand. The asm "string" also contains
"%%eax", which references machine register "%eax". Hard coded registers like "%eax" should be specified
in the clobber list to prevent conflicts with other instructions in the compiler's assembly-language output.Chapter 12. C/C++ Inline Assembly and Intrinsics
135
[output operands], [input operands], and [clobber list] items are described in more detail in the following
sections.
Output Operands
The [output operands] are an optional list of output constraint and expression pairs that specify the result(s)
of the asm statement. An output constraint is a string that specifies how a result is delivered to the expression.
For example, "=r" (x) says the output operand is a write-only register that stores its value in the "C" variable x
at the end of the asm statement. An example follows:
int x;
void example()
{
asm( "movl $0, %0" : "=r" (x) );
}
The previous example assigns 0 to the "C" variable x. For the function in this example, the compiler produces
the following assembly. If you want to produce an assembly listing, compile the example with the pgcc -S
compiler option:
example:
..Dcfb0:
pushq %rbp
..Dcfi0:
movq %rsp, %rbp
..Dcfi1:
..EN1:
## lineno: 8
movl $0, %eax
movl %eax, x(%rip)
## lineno: 0
popq %rbp
ret
In the generated assembly shown, notice that the compiler generated two statements for the asm statement
at line number 5. The compiler generated "movl $0, %eax" from the asm "string". Also notice that %eax
appears in place of "%0" because the compiler assigned the %eax register to variable x. Since item 0 is an
output operand, the result must be stored in its expression (x). The instruction movl %eax, x(%rip) assigns
the output operand to variable x.
In addition to write-only output operands, there are read/write output operands designated with a "+" instead
of a "=". For example, "+r" (x) tells the compiler to initialize the output operand with variable x at the
beginning of the asm statement.
To illustrate this point, the following example increments variable x by 1:
int x=1;
void example2()
{
asm( "addl $1, %0" : "+r" (x) );
}
To perform the increment, the output operand must be initialized with variable x. The read/write constraint
modifier ("+") instructs the compiler to initialize the output operand with its expression. The compiler
generates the following assembly code for the example2() function:PGI® User’s Guide
136
example2:
..Dcfb0:
pushq %rbp
..Dcfi0:
movq %rsp, %rbp
..Dcfi1:
..EN1:
## lineno: 5
movl x(%rip), %eax
addl $1, %eax
movl %eax, x(%rip)
## lineno: 0
popq %rbp
ret
From the example(2) code, two extraneous moves are generated in the assembly: one movl for initializing the
output register and a second movl to write it to variable x. To eliminate these moves, use a memory constraint
type instead of a register constraint type, as shown in the following example:
int x=1;
void example2()
{
asm( "addl $1, %0" : "+m" (x) );
}
The compiler generates a memory reference in place of a memory constraint. This eliminates the two
extraneous moves:
example2:
..Dcfb0:
pushq %rbp
..Dcfi0:
movq %rsp, %rbp
..Dcfi1:
..EN1:
## lineno: 5
addl $1, x(%rip)
## lineno: 0
popq %rbp
ret
Because the assembly uses a memory reference to variable x, it does not have to move x into a register prior to
the asm statement; nor does it need to store the result after the asm statement. Additional constraint types are
found in “Additional Constraints,” on page 139.
The examples thus far have used only one output operand. Because extended asm accepts a list of output
operands, asm statements can have more than one result. For example:
void example4()
{
int x=1;
int y=2;
asm( "addl $1, %1\n" "addl %1, %0": "+r" (x), "+m" (y) );
}
The example above increments variable y by 1 then adds it to variable x. Multiple output operands are
separated with a comma. The first output operand is item 0 ("%0") and the second is item 1 ("%1") in the
asm "string". The resulting values for x and y are 4 and 3 respectively.Chapter 12. C/C++ Inline Assembly and Intrinsics
137
Input Operands
The [input operands] are an optional list of input constraint and expression pairs that specify what "C" values
are needed by the asm statement. The input constraints specify how the data is delivered to the asm statement.
For example, "r" (x) says that the input operand is a register that has a copy of the value stored in "C" variable
x. Another example is "m" (x) which says that the input item is the memory location associated with variable
x. Other constraint types are discussed in “Additional Constraints,” on page 139. An example follows:
void example5()
{
int x=1;
int y=2;
int z=3;
asm( "addl %2, %1\n" "addl %2, %0" : "+r" (x), "+m" (y) : "r" (z) );
}
The previous example adds variable z, item 2, to variable x and variable y. The resulting values for x and y are
4 and 5 respectively.
Another type of input constraint worth mentioning here is the matching constraint. A matching constraint is
used to specify an operand that fills both an input as well as an output role. An example follows:
int x=1;
void example6()
{
asm( "addl $1, %1"
: "=r" (x)
: "0" (x) );
}
The previous example is equivalent to the example2() function shown in “Output Operands,” on page 135.
The constraint/expression pair, "0" (x), tells the compiler to initialize output item 0 with variable x at the
beginning of the asm statement. The resulting value for x is 2. Also note that "%1" in the asm "string" means
the same thing as "%0" in this case. That is because there is only one operand with both an input and an
output role.
Matching constraints are very similar to the read/write output operands mentioned in “Output Operands,”
on page 135. However, there is one key difference between read/write output operands and matching
constraints. The matching constraint can have an input expression that differs from its output expression.
The example below uses different values for the input and output roles:
int x;
int y=2;
void example7()
{
asm( "addl $1, %1"
: "=r" (x)
: "0" (y) );
}
The compiler generates the following assembly for example7():
example7:
..Dcfb0:
pushq %rbp
..Dcfi0:PGI® User’s Guide
138
movq %rsp, %rbp
..Dcfi1:
..EN1:
## lineno: 8
movl y(%rip), %eax
addl $1, %eax
movl %eax, x(%rip)
## lineno: 0
popq %rbp
ret
Variable x gets initialized with the value stored in y, which is 2. After adding 1, the resulting value for variable x
is 3.
Because matching constraints perform an input role for an output operand, it does not make sense for the
output operand to have the read/write ("+") modifier. In fact, the compiler disallows matching constraints
with read/write output operands. The output operand must have a write only ("=") modifier.
Clobber List
The [clobber list] is an optional list of strings that hold machine registers used in the asm "string". Essentially,
these strings tell the compiler which registers may be clobbered by the asm statement. By placing registers
in this list, the programmer does not have to explicitly save and restore them as required in traditional inline
assembly (described in “Inline Assembly,” on page 133). The compiler takes care of any required saving
and restoring of the registers in this list.
Each machine register in the [clobber list] is a string separated by a comma. The leading '%' is optional in the
register name. For example, "%eax" is equivalent to "eax". When specifying the register inside the asm "string",
you must include two leading '%' characters in front of the name (for example., "%%eax"). Otherwise, the
compiler will behave as if a bad input/output operand was specified and generate an error message. An
example follows:
void example8()
{
int x;
int y=2;
asm( "movl %1, %%eax\n"
"movl %1, %%edx\n"
"addl %%edx, %%eax\n"
"addl %%eax, %0"
: "=r" (x)
: "0" (y)
: "eax", "edx" );
}
The code shown above uses two hard-coded registers, eax and edx. It performs the equivalent of 3*y and
assigns it to x, producing a result of 6.
In addition to machine registers, the clobber list may contain the following special flags:
"cc"
The asm statement may alter the condition code register.
"memory"
The asm statement may modify memory in an unpredictable fashion.Chapter 12. C/C++ Inline Assembly and Intrinsics
139
The "memory" flag causes the compiler not to keep memory values cached in registers across the asm
statement and not to optimize stores or loads to that memory. For example:
asm("call MyFunc":::"memory");
This asm statement contains a "memory" flag because it contains a call. The callee may otherwise clobber
registers in use by the caller without the "memory" flag.
The following function uses extended asm and the "cc" flag to compute a power of 2 that is less than or equal
to the input parameter n.
#pragma noinline
int asmDivideConquer(int n)
{
int ax = 0;
int bx = 1;
asm (
"LogLoop:\n"
"cmp %2, %1\n"
"jnle Done\n"
"inc %0\n"
"add %1,%1\n"
"jmp LogLoop\n"
"Done:\n"
"dec %0\n"
:"+r" (ax), "+r" (bx) : "r" (n) : "cc");
return ax;
}
The "cc" flag is used because the asm statement contains some control flow that may alter the
condition code register. The #pragma noinline statement prevents the compiler from inlining the
asmDivideConquer()function. If the compiler inlines asmDivideConquer(), then it may illegally duplicate the
labels LogLoop and Done in the generated assembly.
Additional Constraints
Operand constraints can be divided into four main categories:
• Simple Constraints
• Machine Constraints
• Multiple Alternative Constraints
• Constraint Modifiers
Simple Constraints
The simplest kind of constraint is a string of letters or characters, known as Simple Constraints, such as the
"r" and "m" constraints introduced in “Output Operands,” on page 135. Table 12.1, “Simple Constraints”
describes these constraints.
Table 12.1. Simple Constraints
Constraint Description
whitespace Whitespace characters are ignored.PGI® User’s Guide
140
Constraint Description
E An immediate floating point operand.
F Same as "E".
g Any general purpose register, memory, or immediate integer operand is allowed.
i An immediate integer operand.
m A memory operand. Any address supported by the machine is allowed.
n Same as "i".
o Same as "m".
p An operand that is a valid memory address. The expression associated with the
constraint is expected to evaluate to an address (for example, "p" (&x) ).
r A general purpose register operand.
X Same as "g".
0,1,2,..9 Matching Constraint. See “Input Operands,” on page 137 for a description.
The following example uses the general or "g" constraint, which allows the compiler to pick an appropriate
constraint type for the operand; the compiler chooses from a general purpose register, memory, or immediate
operand. This code lets the compiler choose the constraint type for "y".
void example9()
{
int x, y=2;
asm( "movl %1, %0\n" : "=r"
(x) : "g" (y) );
}
This technique can result in more efficient code. For example, when compiling example9() the compiler
replaces the load and store of y with a constant 2. The compiler can then generate an immediate 2 for the y
operand in the example. The assembly generated by pgcc for our example is as follows:
example9:
..Dcfb0:
pushq %rbp
..Dcfi0:
movq %rsp, %rbp
..Dcfi1:
..EN1:
## lineno: 3
movl $2, %eax
## lineno: 6
popq %rbp
ret
In this example, notice the use of $2 for the "y" operand.
Of course, if y is always 2, then the immediate value may be used instead of the variable with the "i" constraint,
as shown here:
void example10()Chapter 12. C/C++ Inline Assembly and Intrinsics
141
{
int x;
asm( "movl %1, %0\n"
: "=r" (x)
: "i" (2) );
}
Compiling example10() with pgcc produces assembly similar to that produced for example9().
Machine Constraints
Another category of constraints is Machine Constraints. The x86 and x86_64 architectures have several
classes of registers. To choose a particular class of register, you can use the x86/x86_64 machine constraints
described in Table 12.2, “x86/x86_64 Machine Constraints”.
Table 12.2. x86/x86_64 Machine Constraints
Constraint Description
a a register (e.g., %al, %ax, %eax, %rax)
A Specifies a or d registers. This is used primarily for holding 64-bit integer values
on 32 bit targets. The d register holds the most significant bits and the a register
holds the least significant bits.
b b register (e.g, %bl, %bx, %ebx, %rbx)
c c register (e.g., %cl, %cx, %ecx, %rcx)
C Not supported.
d d register (e.g., %dl, %dx, %edx, %rdx)
D di register (e.g., %dil, %di, %edi, %rdi)
e Constant in range of 0xffffffff to 0x7fffffff
f Not supported.
G Floating point constant in range of 0.0 to 1.0.
I Constant in range of 0 to 31 (e.g., for 32-bit shifts).
J Constant in range of 0 to 63 (e.g., for 64-bit shifts)
K Constant in range of 0 to 127.
L Constant in range of 0 to 65535.
M Constant in range of 0 to 3 constant (e.g., shifts for lea instruction).
N Constant in range of 0 to 255 (e.g., for out instruction).
q Same as "r" simple constraint.
Q Same as "r" simple constraint.
R Same as "r" simple constraint.
S si register (e.g., %sil, %si, %edi, %rsi)
t Not supported.
u Not supported.PGI® User’s Guide
142
Constraint Description
x XMM SSE register
y Not supported.
Z Constant in range of 0 to 0x7fffffff.
The following example uses the "x" or XMM register constraint to subtract c from b and store the result in a.
double example11()
{
double a;
double b = 400.99;
double c = 300.98;
asm ( "subpd %2, %0;"
:"=x" (a)
: "0" (b), "x" (c)
);
return a;
}
The generated assembly for this example is this:
example11:
..Dcfb0:
pushq %rbp
..Dcfi0:
movq %rsp, %rbp
..Dcfi1:
..EN1:
## lineno: 4
movsd .C00128(%rip), %xmm1
movsd .C00130(%rip), %xmm2
movapd %xmm1, %xmm0
subpd %xmm2, %xmm0;
## lineno: 10
## lineno: 11
popq %rbp
ret
If a specified register is not available, the pgcc and pgcpp compilers issue an error message. For example,
pgcc and pgcpp reserves the "%ebx" register for Position Independent Code (PIC) on 32-bit system targets. If
a program has an asm statement with a "b" register for one of the operands, the compiler will not be able to
obtain that register when compiling for 32-bit with the -fPIC switch (which generates PIC). To illustrate this
point, the following example is compiled for a 32-bit target using PIC:
void example12()
{
int x=1;
int y=1;
asm( "addl %1, %0\n"
: "+a" (x)
: "b" (y) );
}
Compiling with the "-tp p7" switch chooses a 32-bit target.Chapter 12. C/C++ Inline Assembly and Intrinsics
143
% pgcc example12.c -fPIC -c -tp p7
PGC-S-0354-Can't find a register in class 'BREG' for extended ASM
operand 1 (example12.c: 3)
PGC/x86 Linux/x86 Rel Dev: compilation completed with severe errors
Multiple Alternative Constraints
Sometimes a single instruction can take a variety of operand types. For example, the x86 permits registerto-memory and memory-to-register operations. To allow this flexibility in inline assembly, use multiple
alternative constraints. An alternative is a series of constraints for each operand.
To specify multiple alternatives, separate each alternative with a comma.
Table 12.3. Multiple Alternative Constraints
Constraint Description
, Separates each alternative for a particular operand.
? Ignored
! Ignored
The following example uses multiple alternatives for an add operation.
void example13()
{
int x=1;
int y=1;
asm( "addl %1, %0\n"
: "+ab,cd" (x)
: "db,cam" (y) );
}
example13() has two alternatives for each operand: "ab,cd" for the output operand and "db,cam" for the
input operand. Each operand must have the same number of alternatives; however, each alternative can have
any number of constraints (for example, the output operand in example13() has two constraints for its
second alternative and the input operand has three for its second alternative).
The compiler first tries to satisfy the left-most alternative of the first operand (for example, the output
operand in example13()). When satisfying the operand, the compiler starts with the left-most constraint.
If the compiler cannot satisfy an alternative with this constraint (for example, if the desired register is not
available), it tries to use any subsequent constraints. If the compiler runs out of constraints, it moves on to
the next alternative. If the compiler runs out of alternatives, it issues an error similar to the one mentioned in
example12(). If an alternative is found, the compiler uses the same alternative for subsequent operands. For
example, if the compiler chooses the "c" register for the output operand in example13(), then it will use either
the "a" or "m" constraint for the input operand.
Constraint Modifiers
Characters that affect the compiler's interpretation of a constraint are known as Constraint Modifiers. Two
constraint modifiers, the "=" and the "+", were introduced in “Output Operands,” on page 135. Table 12.4
summarizes each constraint modifier.PGI® User’s Guide
144
Table 12.4. Constraint Modifier Characters
Constraint
Modifier
Description
= This operand is write-only. It is valid for output operands only. If specified, the
"=" must appear as the first character of the constraint string.
+ This operand is both read and written by the instruction. It is valid for output
operands only. The output operand is initialized with its expression before the
first instruction in the asm statement. If specified, the "+" must appear as the first
character of the constraint string.
& A constraint or an alternative constraint, as defined in “Multiple Alternative
Constraints,” on page 143, containing an "&" indicates that the output operand
is an early clobber operand. This type operand is an output operand that may be
modified before the asm statement finishes using all of the input operands. The
compiler will not place this operand in a register that may be used as an input
operand or part of any memory address.
% Ignored.
# Characters following a "#" up to the first comma (if present) are to be ignored in
the constraint.
* The character that follows the "*" is to be ignored in the constraint.
The "=" and "+" modifiers apply to the operand, regardless of the number of alternatives in the constraint
string. For example, the "+" in the output operand of example13() appears once and applies to both
alternatives in the constraint string. The "&", "#", and "*" modifiers apply only to the alternative in which they
appear.
Normally, the compiler assumes that input operands are used before assigning results to the output operands.
This assumption lets the compiler reuse registers as needed inside the asm statement. However, if the asm
statement does not follow this convention, the compiler may indiscriminately clobber a result register with an
input operand. To prevent this behavior, apply the early clobber "&" modifier. An example follows:
void example15()
{
int w=1;
int z;
asm( "movl $1, %0\n"
"addl %2, %0\n"
"movl %2, %1"
: "=a" (w), "=r" (z) : "r" (w) );
}
The previous code example presents an interesting ambiguity because "w" appears both as an output and as
an input operand. So, the value of "z" can be either 1 or 2, depending on whether the compiler uses the same
register for operand 0 and operand 2. The use of constraint "r" for operand 2 allows the compiler to pick
any general purpose register, so it may (or may not) pick register "a" for operand 2. This ambiguity can be
eliminated by changing the constraint for operand 2 from "r" to "a" so the value of "z" will be 2, or by adding
an early clobber "&" modifier so that "z" will be 1. The following example shows the same function with an
early clobber "&" modifier:Chapter 12. C/C++ Inline Assembly and Intrinsics
145
void example16()
{
int w=1;
int z;
asm( "movl $1, %0\n"
"addl %2, %0\n"
"movl %2, %1"
: "=&a" (w), "=r" (z) : "r" (w) );
}
Adding the early clobber "&" forces the compiler not to use the "a" register for anything other than operand 0.
Operand 2 will therefore get its own register with its own copy of "w". The result for "z" in example16() is 1.
Operand Aliases
Extended asm specifies operands in assembly strings with a percent '%' followed by the operand number. For
example, "%0" references operand 0 or the output item "=&a" (w) in function example16() shown above.
Extended asm also supports operand aliasing, which allows use of a symbolic name instead of a number for
specifying operands. An example follows:
void example17()
{
int w=1, z=0;
asm( "movl $1, %[output1]\n"
"addl %[input], %[output1]\n"
"movl %[input], %[output2]"
: [output1] "=&a" (w), [output2] "=r"
(z)
: [input] "r" (w));
}
In example17(), "%[output1]" is an alias for "%0", "%[output2]" is an alias for "%1", and "%[input]" is an
alias for "%2". Aliases and numeric references can be mixed, as shown in the following example:
void example18()
{
int w=1, z=0;
asm( "movl $1, %[output1]\n"
"addl %[input], %0\n"
"movl %[input], %[output2]"
: [output1] "=&a" (w), [output2] "=r" (z)
: [input] "r" (w));
}
In example18(), "%0" and "%[output1]" both represent the output operand.
Assembly String Modifiers
Special character sequences in the assembly string affect the way the assembly is generated by the compiler.
For example, the "%" is an escape sequence for specifying an operand, "%%" produces a percent for hard
coded registers, and "\n" specifies a new line. Table 12.5, “Assembly String Modifier Characters”summarizes
these modifiers, known as Assembly String Modifiers.
Table 12.5. Assembly String Modifier Characters
Modifier Description
\ Same as \ in printf format strings.PGI® User’s Guide
146
Modifier Description
%* Adds a '*' in the assembly string.
%% Adds a '%' in the assembly string.
%A Adds a '*' in front of an operand in the assembly string. (For example, %A0 adds
a '*' in front of operand 0 in the assembly output.)
%B Produces the byte op code suffix for this operand. (For example, %b0 produces
'b' on x86 and x86_64.)
%L Produces the word op code suffix for this operand. (For example, %L0 produces
'l' on x86 and x86_64.)
%P If producing Position Independent Code (PIC), the compiler adds the PIC suffix
for this operand. (For example, %P0 produces @PLT on x86 and x86_64.)
%Q Produces a quad word op code suffix for this operand if is supported by the
target. Otherwise, it produces a word op code suffix. (For example, %Q0
produces 'q' on x86_64 and 'l' on x86.)
%S Produces 's' suffix for this operand. (For example, %S0 produces 's' on x86 and
x86_64.)
%T Produces 't' suffix for this operand. (For example, %S0 produces 't' on x86 and
x86_64.)
%W Produces the half word op code suffix for this operand. (For example, %W0
produces 'w' on x86 and x86_64.)
%a Adds open and close parentheses ( ) around the operand.
%b Produces the byte register name for an operand. (For example, if operand 0 is in
register 'a', then %b0 will produce '%al'.)
%c Cuts the '$' character from an immediate operand.
%k Produces the word register name for an operand. (For example, if operand 0 is
in register 'a', then %k0 will produce '%eax'.)
%q Produces the quad word register name for an operand if the target supports
quad word. Otherwise, it produces a word register name. (For example, if
operand 0 is in register 'a', then %q0 produces %rax on x86_64 or %eax on
x86.)
%w Produces the half word register name for an operand. (For example, if operand
0 is in register 'a', then %w0 will produce '%ax'.)
%z Produces an op code suffix based on the size of an operand. (For example, 'b'
for byte, 'w' for half word, 'l' for word, and 'q' for quad word.)
%+ %C %D
%F %O %X
%f %h %l %n
%s %y
Not Supported.
These modifiers begin with either a backslash "\" or a percent "%".Chapter 12. C/C++ Inline Assembly and Intrinsics
147
The modifiers that begin with a backslash "\" (e.g., "\n") have the same effect as they do in a printf format
string. The modifiers that are preceded with a "%" are used to modify a particular operand.
These modifiers begin with either a backslash "\" or a percent "%" For example, "%b0" means, "produce the
byte or 8 bit version of operand 0". If operand 0 is a register, it will produce a byte register such as %al, %bl,
%cl, and so on.
Consider this example:
void example19()
{
int a = 1;
int *p = &a;
asm ("add%z0 %q1, %a0"
: "=&p" (p) : "r" (a), "0" (p) );
}
On an x86 target, the compiler produces the following instruction for the asm string shown in the preceding
example:
addl %ecx, (%eax)
The "%z0" modifier produced an 'l' (lower-case 'L') suffix because the size of pointer p is 32 bits on x86.
The "%q1" modifier produced the word register name for variable a. The "%a0" instructs the compiler to add
parentheses around operand 0, hence "(%eax)".
On an x86_64 target, the compiler produces the following instruction for the above asm string shown in the
preceding example:
addq %rcx, (%rax)
The "%z0" modifier produced a 'q' suffix because the size of pointer p is 64-bit on x86_64. Because x86_64
supports quad word registers, the "%q1" modifier produced the quad word register name (%rax) for variable
a.
Extended Asm Macros
As with traditional inline assembly, described in“Inline Assembly,” on page 133, extended asm can be used
in a macro. For example, you can use the following macro to access the runtime stack pointer.
#define GET_SP(x) \
asm("mov %%sp, %0": "=m" (##x):: "%sp" );
void example20()
{
void * stack_pointer;
GET_SP(stack_pointer);
}
The GET_SP macro assigns the value of the stack pointer to whatever is inserted in its argument (for example,
stack_pointer). Another "C" extension known as statement expressions is used to write the GET_SP macro
another way:
#define GET_SP2 ({ \
void *my_stack_ptr; \
asm("mov %%sp, %0": "=m" (my_stack_ptr) :: "%sp" ); \PGI® User’s Guide
148
my_stack_ptr; \
})
void example21()
{
void * stack_pointer = GET_SP2;
}
The statement expression allows a body of code to evaluate to a single value. This value is specified as the last
instruction in the statement expression. In this case, the value is the result of the asm statement, my_stack_ptr.
By writing an asm macro with a statement expression, the asm result may be assigned directly to another
variable (for example, void * stack_pointer = GET_SP2) or included in a larger expression, such as: void *
stack_pointer = GET_SP2 - sizeof(long).
Which style of macro to use depends on the application. If the asm statement needs to be a part of an
expression, then a macro with a statement expression is a good approach. Otherwise, a traditional macro, like
GET_SP(x), will probably suffice.
Intrinsics
Inline intrinsic functions map to actual x86 or x64 machine instructions. Intrinsics are inserted inline to avoid
the overhead of a function call. The compiler has special knowledge of intrinsics, so with use of intrinsics,
better code may be generated as compared to extended inline assembly code.
The PGI Workstation version 7.0 or higher compiler intrinsics library implements MMX, SSE, SS2, SSE3, SSSE3,
SSE4a, and ABM instructions. The intrinsic functions are available to C and C++ programs on Linux and
Windows.
Unlike most functions which are in libraries, intrinsics are implemented internally by the compiler. A program
can call the intrinsic functions from C/C++ source code after including the corresponding header file.
The intrinsics are divided into header files as follows:
Table 12.6. Intrinsic Header File Organization
Instructions Header File
MMX mmintrin.h
SSE xmmintrin.h
SSE2 emmintrin.h
SSE3 pmmintrin.h
SSSE3 tmmintrin.h
SSE4a ammintrin.h
ABM intrin.h
The following is a simple example program that calls XMM intrinsics.
#include
int main(){
__m128 __A, __B,
result;Chapter 12. C/C++ Inline Assembly and Intrinsics
149
__A = _mm_set_ps(23.3,
43.7, 234.234, 98.746);
__B = _mm_set_ps(15.4,
34.3, 4.1, 8.6);
result = _mm_add_ps(__A,__B);
return 0;
}150151
Chapter 13. Fortran, C and C++
Data Types
This chapter describes the scalar and aggregate data types recognized by the PGI Fortran, C, and C++
compilers, the format and alignment of each type in memory, and the range of values each type can have
on x86 or x64 processor-based systems running a 32-bit operating system. For more information on x86-
specific data representation, refer to the System V Application Binary Interface, Processor Supplement, listed in
“Related Publications,” on page xxvii. This chapter specifically does not address x64 processor-based systems
running a 64-bit operating system, because the application binary interface (ABI) for those systems is still
evolving. For the latest version of the ABI, refer to http://www.x86-64.org/abi.pdf.
Fortran Data Types
Fortran Scalars
A scalar data type holds a single value, such as the integer value 42 or the real value 112.6. The next table lists
scalar data types, their size, format and range. Table 13.2, “Real Data Type Ranges,” on page 152 shows the
range and approximate precision for Fortran real data types. Table 13.3, “Scalar Type Alignment,” on page
152 shows the alignment for different scalar data types. The alignments apply to all scalars, whether they are
independent or contained in an array, a structure or a union.
Table 13.1. Representation of Fortran Data Types
Fortran Data Type Format Range
INTEGER 2's complement integer
-2
31
to 2
31
-1
INTEGER*2 2's complement integer -32768 to 32767
INTEGER*4 2's complement integer
INTEGER*8 2's complement integer
-2
63
to 2
63
-1
LOGICAL 32-bit value true or false
LOGICAL*1 8-bit value true or falsePGI® User’s Guide
152
Fortran Data Type Format Range
LOGICAL*2 16-bit value true or false
LOGICAL*4 32-bit value true or false
LOGICAL*8 64-bit value true or false
BYTE 2's complement -128 to 127
REAL Single-precision floating point
10
-37
to 1038
(1)
REAL*4 Single-precision floating point
10
-37
to 1038
(1)
REAL*8 Double-precision floating point
10
-307
to 1038
(1)
DOUBLE PRECISION Double-precision floating point
10
-307
to 1038
(1)
COMPLEX Single-precision floating point
10
-37
to 1038
(1)
DOUBLE COMPLEX Double-precision floating point
10
-307
to 1038
(1)
COMPLEX*16 Double-precision floating point
10
-307
to 1038
(1)
CHARACTER*n Sequence of n bytes
(1)
Approximate value
The logical constants .TRUE. and .FALSE. are all ones and all zeroes, respectively. Internally, the value of
a logical variable is true if the least significant bit is one and false otherwise. When the option –Munixlogical is
set, a logical variable with a non-zero value is true and with a zero value is false.
Table 13.2. Real Data Type Ranges
Data Type Binary Range Decimal Range Digits of Precision
REAL
-2
-126
to 2
128
10
-37
to 1038
(1) 7-8
REAL*8
-2
-1022
to 2
1024
10
-307
to 1038
(1) 15-16
Table 13.3. Scalar Type Alignment
This Type... ...Is aligned on this size boundary
LOGICAL*1 1-byte
LOGICAL*2 2-byte
LOGICAL*4 4-byte
LOGICAL*8 8-byte
BYTE 1-byteChapter 13. Fortran, C and C++ Data Types
153
This Type... ...Is aligned on this size boundary
INTEGER*2 2-byte
INTEGER*4 4-byte
INTEGER*8 8-byte
REAL*4 4-byte
REAL*8 8-byte
COMPLEX*8 4-byte
COMPLEX*16 8-byte
FORTRAN 77 Aggregate Data Type Extensions
The PGF77 compiler supports de facto standard extensions to FORTRAN 77 that allow for aggregate data
types. An aggregate data type consists of one or more scalar data type objects. You can declare the following
aggregate data types:
array
consists of one or more elements of a single data type placed in contiguous locations from first to last.
structure
is a structure that can contain different data types. The members are allocated in the order they appear in
the definition but may not occupy contiguous locations.
union
is a single location that can contain any of a specified set of scalar or aggregate data types. A union can
have only one value at a time. The data type of the union member to which data is assigned determines the
data type of the union after that assignment.
The alignment of an array, a structure or union (an aggregate) affects how much space the object occupies
and how efficiently the processor can address members. Arrays use the alignment of their members.
Array types
align according to the alignment of the array elements. For example, an array of INTEGER*2 data aligns on
a 2-byte boundary.
Structures and Unions
align according to the alignment of the most restricted data type of the structure or union. In the next
example, the union aligns on a 4-byte boundary since the alignment of c, the most restrictive element, is
four.
STRUCTURE /astr/
UNION
MAP
INTEGER*2 a ! 2 bytes
END MAP PGI® User’s Guide
154
MAP
BYTE b ! 1 byte
END MAP
MAP
INTEGER*4 c ! 4 bytes
END MAP
END UNION
END STRUCTURE
Structure alignment can result in unused space called padding. Padding between members of the structure is
called internal padding. Padding between the last member and the end of the space is called tail padding.
The offset of a structure member from the beginning of the structure is a multiple of the member’s alignment.
For example, since an INTEGER*2 aligns on a 2-byte boundary, the offset of an INTEGER*2 member from the
beginning of a structure is a multiple of two bytes.
Fortran 90 Aggregate Data Types (Derived Types)
The Fortran 90 standard added formal support for aggregate data types. The TYPE statement begins a derived
type data specification or declares variables of a specified user-defined type. For example, the following would
define a derived type ATTENDEE:
TYPE ATTENDEE
CHARACTER(LEN=30) NAME
CHARACTER(LEN=30) ORGANIZATION
CHARACTER (LEN=30) EMAIL
END TYPE ATTENDEE
In order to declare a variable of type ATTENDEE and access the contents of such a variable, code such as the
following would be used:
TYPE (ATTENDEE) ATTLIST(100)
. . .
ATTLIST(1)%NAME = ‘JOHN DOE’
C and C++ Data Types
C and C++ Scalars
Table 13.4, “C/C++ Scalar Data Types”lists C and C++ scalar data types, providing their size and format.
The alignment of a scalar data type is equal to its size. Table 13.5, “Scalar Alignment,” on page 155 shows
scalar alignments that apply to individual scalars and to scalars that are elements of an array or members of a
structure or union. Wide characters are supported (character constants prefixed with an L). The size of each
wide character is 4 bytes.
Table 13.4. C/C++ Scalar Data Types
Data Type Size
(bytes)
Format Range
unsigned char 1 ordinal 0 to 255
[signed] char 1 2's complement integer -128 to 127
unsigned short 2 ordinal 0 to 65535
[signed] short 2 2's complement integer -32768 to 32767Chapter 13. Fortran, C and C++ Data Types
155
Data Type Size
(bytes)
Format Range
unsigned int 4 ordinal
0 to 2
32
-1
[signed] int 4 2's complement integer
-2
31
to 2
31
-1
[signed] long [int] (32-bit
operating systems and win64)
4 2's complement integer
-2
31
to 2
31
-1
[signed] long [int] (linux86-
64 and sua64)
8 2's complement integer
-2
63
to 2
63
-1
unsigned long [int] (32-bit
operating systems and win64)
4 ordinal
0 to 2
32
-1
unsigned long [int] (linux86-
64 and sua64)
8 ordinal
0 to 2
64
-1
[signed] long long [int] 8 2's complement integer
-2
63
to 2
63
-1
unsigned long long [int] 8 ordinal
0 to 2
64
-1
float 4 IEEE single-precision
floating-point
10
-37
to 10
38
(1)
double 8 IEEE double-precision
floating-point
10
-307
to 10
308
(1)
long double 8 IEEE double-precision
floating-point
10
-307
to 10
308
(1)
bit field
(2)
(unsigned value)
1 to 32
bits
ordinal
0 to 2
size
-1, where size is the
number of bits in the bit field
bit field
(2)
(signed value)
1 to 32
bits
2's complement integer
-2
size-1
to 2
size-1
-1, where size
is the number of bits in the bit
field
pointer 4 address
0 to 2
32
-1
enum 4 2's complement integer
-2
31
to 2
31
-1
(1)
Approximate value
(2)
Bit fields occupy as many bits as you assign them, up to 4 bytes, and their length need not be a multiple of 8
bits (1 byte)
Table 13.5. Scalar Alignment
Data Type Alignment on this size boundary
char 1-byte boundary, signed or unsigned.
short 2-byte boundary, signed or unsigned.
int 4-byte boundary, signed or unsigned.PGI® User’s Guide
156
Data Type Alignment on this size boundary
enum 4-byte boundary.
pointer 4-byte boundary.
float 4-byte boundary.
double 8-byte boundary.
long double 8-byte boundary.
long [int] 32-bit on Win64 4-byte boundary, signed or unsigned.
long [int] linux86-64, sua64 8-byte boundary, signed or unsigned.
long long [int] 8-byte boundary, signed or unsigned.
C and C++ Aggregate Data Types
An aggregate data type consists of one or more scalar data type objects. You can declare the following
aggregate data types:
array
consists of one or more elements of a single data type placed in contiguous locations from first to last.
class
(C++ only) is a class that defines an object and its member functions. The object can contain fundamental
data types or other aggregates including other classes. The class members are allocated in the order they
appear in the definition but may not occupy contiguous locations.
struct
is a structure that can contain different data types. The members are allocated in the order they appear in
the definition but may not occupy contiguous locations. When a struct is defined with member functions,
its alignment rules are the same as those for a class.
union
is a single location that can contain any of a specified set of scalar or aggregate data types. A union can
have only one value at a time. The data type of the union member to which data is assigned determines the
data type of the union after that assignment.
Class and Object Data Layout
Class and structure objects with no virtual entities and with no base classes, that is just direct data field
members, are laid out in the same manner as C structures. The following section describes the alignment and
size of these C-like structures. C++ classes (and structures as a special case of a class) are more difficult to
describe. Their alignment and size is determined by compiler generated fields in addition to user-specified
fields. The following paragraphs describe how storage is laid out for more general classes. The user is warned
that the alignment and size of a class (or structure) is dependent on the existence and placement of direct
and virtual base classes and of virtual function information. The information that follows is for informational
purposes only, reflects the current implementation, and is subject to change. Do not make assumptions about
the layout of complex classes or structures.
All classes are laid out in the same general way, using the following pattern (in the sequence indicated):Chapter 13. Fortran, C and C++ Data Types
157
• First, storage for all of the direct base classes (which implicitly includes storage for non-virtual indirect
base classes as well):
• When the direct base class is also virtual, only enough space is set aside for a pointer to the actual
storage, which appears later.
• In the case of a non-virtual direct base class, enough storage is set aside for its own non-virtual base
classes, its virtual base class pointers, its own fields, and its virtual function information, but no space is
allocated for its virtual base classes.
• Next, storage for the class’s own fields.
• Next, storage for virtual function information (typically, a pointer to a virtual function table).
• Finally, storage for its virtual base classes, with space enough in each case for its own non-virtual base
classes, virtual base class pointers, fields, and virtual function information.
Aggregate Alignment
The alignment of an array, a structure or union (an aggregate) affects how much space the object occupies
and how efficiently the processor can address members.
Arrays
align according to the alignment of the array elements. For example, an array of short data type aligns on a
2-byte boundary.
Structures and Unions
align according to the most restrictive alignment of the enclosing members. For example the union un1
below aligns on a 4-byte boundary since the alignment of c, the most restrictive element, is four:
union un1 {
short a; /* 2 bytes */
char b; /* 1 byte */
int c; /* 4 bytes */
};
Structure alignment can result in unused space, called padding. Padding between members of a structure is
called internal padding. Padding between the last member and the end of the space occupied by the structure
is called tail padding. Figure 13.1, “Internal Padding in a Structure,” on page 157, illustrates structure
alignment. Consider the following structure:
struct strc1 {
char a; /* occupies byte 0 */
short b; /* occupies bytes 2 and 3 */
char c; /* occupies byte 4 */
int d; /* occupies bytes 8 through 11 */
};
Figure 13.1. Internal Padding in a StructurePGI® User’s Guide
158
Figure 13.2, “Tail Padding in a Structure,” on page 158, shows how tail padding is applied to a structure
aligned on a doubleword (8 byte) boundary.
struct strc2{
int m1[4]; /* occupies bytes
0 through 15 */
double m2; /* occupies bytes 16 through 23 */
short m3; /* occupies bytes 24 and 25 */
} st;
Bit-field Alignment
Bit-fields have the same size and alignment rules as other aggregates, with several additions to these rules:
• Bit-fields are allocated from right to left.
• A bit-field must entirely reside in a storage unit appropriate for its type. Bit-fields never cross unit
boundaries.
• Bit-fields may share a storage unit with other structure/union members, including members that are not bitfields.
• Unnamed bit-field's types do not affect the alignment of a structure or union.
• Items of [signed/unsigned] long long type may not appear in field declarations on 32-bit systems.
Figure 13.2. Tail Padding in a Structure
Other Type Keywords in C and C++
The void data type is neither a scalar nor an aggregate. You can use void or void* as the return type of
a function to indicate the function does not return a value, or as a pointer to an unspecified data type,
respectively.
The const and volatile type qualifiers do not in themselves define data types, but associate attributes with other
types. Use const to specify that an identifier is a constant and is not to be changed. Use volatile to prevent
optimization problems with data that can be changed from outside the program, such as memory#mapped I/O
buffers.159
Chapter 14. C++ Name Mangling
Name mangling transforms the names of entities so that the names include information on aspects of the
entity’s type and fully qualified name. This ability is necessary since the intermediate language into which
a program is translated contains fewer and simpler name spaces than there are in the C++ language;
specifically:
• Overloaded function names are not allowed in the intermediate language.
• Classes have their own scopes in C++, but not in the generated intermediate language. For example, an
entity x from inside a class must not conflict with an entity x from the file scope.
• External names in the object code form a completely flat name space. The names of entities with external
linkage must be projected onto that name space so that they do not conflict with one another. A function f
from a class A, for example, must not have the same external name as a function f from class B.
• Some names are not names in the conventional sense of the word, they're not strings of alphanumeric
characters, for example: operator=.
There are two main problems here:
1. Generating external names that will not clash.
2. Generating alphanumeric names for entities with strange names in C++.
Name mangling solves these problems by generating external names that will not clash, and alphanumeric
names for entities with strange names in C++. It also solves the problem of generating hidden names for some
behind-the-scenes language support in such a way that they match up across separate compilations.
You see mangled names if you view files that are translated by PGC++, and you do not use tools that demangle
the C++ names. Intermediate files that use mangled names include the assembly and object files created by the
pgcpp command. To view demangled names, use the tool pgdecode, which takes input from stdin.
prompt> pgdecode
g__1ASFf
A::g(float)
The name mangling algorithm for the PGC++ compiler is the same as that for cfront, and, except for a few
minor details, also matches the description in Section 7.2, Function Name Encoding, of The Annotated C++
Reference Manual (ARM). Refer to the ARM for a complete description of name mangling.PGI® User’s Guide
160
Types of Mangling
The following entity names are mangled:
• Function names including non-member function names are mangled, to deal with overloading. Names of
functions with extern "C" linkage are not mangled.
• Mangled function names have the function name followed by __ followed by F followed by the mangled
description of the types of the parameters of the function. If the function is a member function, the mangled
form of the class name precedes the F. If the member function is static, an S also precedes the F.
int f(float); // f__Ff
class A
int f(float); // f__1AFf
static int g(float); // g__1ASFf
;
• Special and operator function names, like constructors and operator=(). The encoding is similar to that for
normal functions, but a coded name is used instead of the routine name:
class A
int operator+(float); // __pl__1Aff
A(float); // __ct__1Aff
;
int operator+(A, float); // __pl__F1Af
• Static data member names. The mangled form is the member name followed by __ followed by the mangled
form of the class name:
class A
static int i; // i__1A
;
• Names of variables generated for virtual function tables. These have names like vtblmangled-classname or vtblmangled-base-class-namemangled-class-name.
• Names of variables generated to contain runtime type information. These have names like Ttypeencoding and TIDtype-encoding.
Mangling Summary
This section lists some of the C++ entities that are mangled and provides some details on the mangling
algorithm. For more details, refer to The Annotated C++ Reference Manual.
Type Name Mangling
Using PGC++, each type has a corresponding mangled encoding. For example, a class type is represented as
the class name preceded by the number of characters in the class name, as in 5abcde for abcde. Simple
types are encoded as lower-case letters, as in i for int or f for float. Type modifiers and declarators are
encoded as upper-case letters preceding the types they modify, as in U for unsigned or P for pointer.Chapter 14. C++ Name Mangling
161
Nested Class Name Mangling
Nested class types are encoded as a Q followed by a digit indicating the depth of nesting, followed by a _,
followed by the mangled-form names of the class types in the fully-qualified name of the class, from outermost
to innermost:
class A
class B // Q2_1A1B
;
;
Local Class Name Mangling
The name of the nested class itself is mangled to the form described above with a prefix __, which serves to
make the class name distinct from all user names. Local class names are encoded as L followed by a number
(which has no special meaning; it’s just an identifying number assigned to the class) followed by __ followed
by the mangled name of the class (this is not in the ARM, and cfront encodes local class names slightly
differently):
void f()
class A // L1__1A}
;
;
This form is used when encoding the local class name as a type. It’s not necessary to mangle the name of the
local class itself unless it's also a nested class.
Template Class Name Mangling
Template classes have mangled names that encode the arguments of the template:
template class abc ;
abc x;
abc__pt__3_ii
This describes two template arguments of type int with the total length of template argument list string,
including the underscore, and a fixed string, indicates parameterized type as well, the name of the class
template.162163
Chapter 15. Command-Line Options
Reference
A command-line option allows you to specify specific behavior when a program is compiled and linked.
Compiler options perform a variety of functions, such as setting compiler characteristics, describing the
object code to be produced, controlling the diagnostic messages emitted, and performing some preprocessor
functions. Most options that are not explicitly set take the default settings. This reference chapter describes the
syntax and operation of each compiler option. For easy reference, the options are arranged in alphabetical
order.
For an overview and tips on which options are best for which tasks, refer to Chapter 2, “Using Command Line
Options,” on page 15, which also provides summary tables of the different options.
This chapter uses the following notation:
[item]
Square brackets indicate that the enclosed item is optional.
{item | item}
Braces indicate that you must select one and only one of the enclosed items. A vertical bar (|) separates
the choices.
...
Horizontal ellipses indicate that zero or more instances of the preceding item are valid.
PGI Compiler Option Summary
The following tables include all the PGI compiler options that are not language-specific. The options are
separated by category for easier reference.
For a complete description of each option, see the detailed information later in this chapter.
Build-Related PGI Options
The options included in the following table are the ones you use when you are initially building your program
or application.PGI® User’s Guide
164
Table 15.1. PGI Build-Related Compiler Options
Option Description
–# Display invocation information.
–### Show but do not execute the driver commands (same as –dryrun).
–c Stops after the assembly phase and saves the object code in
filename.o.
–D Defines a preprocessor macro.
–d Prints additional information from the preprocessor.
–dryrun Show but do not execute driver commands.
–E Stops after the preprocessing phase and displays the preprocessed
file on the standard output.
–F Stops after the preprocessing phase and saves the preprocessed
file in filename.f (this option is only valid for the PGI Fortran
compilers).
--flagcheck Simply return zero status if flags are correct.
–flags Display valid driver options.
–fpic (Linux only) Generate position-independent code.
–fPIC (Linux only) Equivalent to –fpic.
–G (Linux only) Passed to the linker. Instructs the linker to produce a
shared object file.
–g77libs (Linux only) Allow object files generated by g77 to be linked into
PGI main programs.
–help Display driver help message.
–I Adds a directory to the search path for #include files.
–i2, –i4 and –i8 –i2: Treat INTEGER variables as 2 bytes.
–i4: Treat INTEGER variables as 4 bytes.
–i8: Treat INTEGER and LOGICAL variables as 8 bytes and use 64-
bits for INTEGER*8 operations.
–K Requests special compilation semantics with regard to conformance
to IEEE 754.
--keeplnk If the compiler generates a temporary indirect file for a long linker
command, preserves the temporary file instead of deleting it.
–L Specifies a library directory.
–l Loads a library.
–m Displays a link map on the standard output.
–M Selects variations for code generation and optimization.
–mcmodel=mediumChapter 15. Command-Line Options Reference
165
Option Description
(–tp k8-64 and –tp p7-64 targets only) Generate code which
supports the medium memory model in the linux86-64
environment.
–module (F90/F95/HPF only) Save/search for module files in directory
.
–mp[=align,[no]numa] Interpret and process user-inserted shared-memory parallel
programming directives (see Chapters 5 and 6).
–noswitcherror Ignore unknown command line switches after printing an warning
message.
–o Names the object file.
–pc (–tp px/p5/p6/piii targets only) Set precision globally for x87
floating-point calculations; must be used when compiling the main
program. may be one of 32, 64 or 80.
–pg Instrument the generated executable to produce a gprof-style
gmon.out sample-based profiling trace file (–qp is also supported,
and is equivalent).
–pgf77libs Append PGF77 runtime libraries to the link line.
–pgf90libs Append PGF90/PGF95 runtime libraries to the link line.
–Q Selects variations for compiler steps.
–R (Linux only) Passed to the Linker. Hard code into the
search path for shared object files.
–r Creates a relocatable object file.
–r4 and –r8 –r4: Interpret DOUBLE PRECISION variables as REAL.
–r8: Interpret REAL variables as DOUBLE PRECISION.
–rc file Specifies the name of the driver's startup file.
–s Strips the symbol-table information from the object file.
–S Stops after the compiling phase and saves the assembly–language
code in filename.s.
–shared (Linux only) Passed to the linker. Instructs the linker to generate a
shared object file. Implies –fpic.
–show Display driver's configuration parameters after startup.
–silent Do not print warning messages.
–soname Pass the soname option and its argument to the linker.
–time Print execution times for the various compilation steps.
–tp [,target...] Specify the type(s) of the target processor(s).PGI® User’s Guide
166
Option Description
–u Initializes the symbol table with , which is undefined for
the linker. An undefined symbol triggers loading of the first member
of an archive library.
–U Undefine a preprocessor macro.
–V[release_number] Displays the version messages and other information, or allows
invocation of a version of the compiler other than the default.
–v Displays the compiler, assembler, and linker phase invocations.
–W Passes arguments to a specific phase.
–w Do not print warning messages.
PGI Debug-Related Compiler Options
The options included in the following table are the ones you typically use when you are debugging your
program or application.
Table 15.2. PGI Debug-Related Compiler Options
Option Description
–C Exposes Ansi warnings only.
–c Instrument the generated executable to perform array bounds
checking at runtime.
–E Stops after the preprocessing phase and displays the preprocessed
file on the standard output.
--flagcheck Simply return zero status if flags are correct.
–flags Display valid driver options.
–g Includes debugging information in the object module.
–gopt Includes debugging information in the object module, but forces
assembly code generation identical to that obtained when is not
present on the command line.
–K Requests special compilation semantics with regard to conformance
to IEEE 754.
--keeplnk If the compiler generates a temporary indirect file for a long linker
command, preserves the temporary file instead of deleting it.
–M Selects variations for code generation and optimization.
–pc (–tp px/p5/p6/piii targets only) Set precision globally for x87
floating-point calculations; must be used when compiling the main
program. may be one of 32, 64 or 80.
–Mprof=timeChapter 15. Command-Line Options Reference
167
Option Description
Instrument the generated executable to produce a gprof-style
gmon.out sample-based profiling trace file (–qp is also supported,
and is equivalent).
PGI Optimization-Related Compiler Options
The options included in the following table are the ones you typically use when you are optimizing your
program or application code.
Table 15.3. Optimization-Related PGI Compiler Options
Option Description
–fast Generally optimal set of flags for targets that support SSE capability.
–fastsse Generally optimal set of flags for targets that include SSE/SSE2
capability.
–M Selects variations for code generation and optimization.
–mp[=align,[no]numa] Interpret and process user-inserted shared-memory parallel
programming directives (see Chapters 5 and 6).
–nfast Generally optimal set of flags for the target. Doesn’t use SSE.
–O Specifies code optimization level where is 0, 1, 2, 3, or 4.
–pc (–tp px/p5/p6/piii targets only) Set precision globally for x87
floating-point calculations; must be used when compiling the main
program. may be one of 32, 64 or 80.
–Mprof=time Instrument the generated executable to produce a gprof-style
gmon.out sample-based profiling trace file (-qp is also supported,
and is equivalent).
PGI Linking and Runtime-Related Compiler Options
The options included in the following table are the ones you typically use to define parameters related to
linking and running your program or application code.
Table 15.4. Linking and Runtime-Related PGI Compiler Options
Option Description
–byteswapio (Fortran only) Swap bytes from big-endian to little-endian or vice
versa on input/output of unformatted data
–fpic (Linux only) Generate position-independent code.
–fPIC (Linux only) Equivalent to –fpic.
–G (Linux only) Passed to the linker. Instructs the linker to produce a
shared object file.PGI® User’s Guide
168
Option Description
–g77libs (Linux only) Allow object files generated by g77 to be linked into
PGI main programs.
–i2, –i4 and –i8 –i2: Treat INTEGER variables as 2 bytes.
–i4: Treat INTEGER variables as 4 bytes.
–i8: Treat INTEGER and LOGICAL variables as 8 bytes and use 64-
bits for INTEGER*8 operations.
–K Requests special compilation semantics with regard to conformance
to IEEE 754.
–M Selects variations for code generation and optimization.
–mcmodel=medium (–tp k8-64 and –tp p7-64 targets only) Generate code which
supports the medium memory model in the linux86-64
environment.
–shared (Linux only) Passed to the linker. Instructs the linker to generate a
shared object file. Implies –fpic.
–soname Pass the soname option and its argument to the linker.
–tp [,target...] Specify the type(s) of the target processor(s).
C and C++ Compiler Options
There are a large number of compiler options specific to the PGCC and PGC++ compilers, especially PGC++.
The next table lists several of these options, but is not exhaustive. For a complete list of available options,
including an exhaustive list of PGC++ options, use the –help command-line option. For further detail on a
given option, use –help and specify the option explicitly. The majority of these options are related to building
your program or application.
Table 15.5. C and C++ -specific Compiler Options
Option Description
–A (pgcpp only) Accept proposed ANSI C++, issuing errors
for non-conforming code.
–a (pgcpp only) Accept proposed ANSI C++, issuing
warnings for non-conforming code.
--[no_]alternative_tokens (pgcpp only) Enable/disable recognition of alternative
tokens. These are tokens that make it possible to write
C++ without the use of the , , [, ], #, &, and ^ and
characters. The alternative tokens include the operator
keywords (e.g., and, bitand, etc.) and digraphs. The
default is -–no_alternative_tokens.
–B Allow C++ comments (using //) in C source.
–b (pgcpp only) Compile with cfront 2.1 compatibility. This
accepts constructs and a version of C++ that is not partChapter 15. Command-Line Options Reference
169
Option Description
of the language definition but is accepted by cfront. EDG
option.
–b3 (pgcpp only) Compile with cfront 3.0 compatibility. See
–b above.
--[no_]bool (pgcpp only) Enable or disable recognition of bool. The
default value is ––bool.
– –[no_]builtin Do/don’t compile with math subroutine builtin support,
which causes selected math library routines to be
inlined. The default is ––builtin.
--cfront_2.1 (pgcpp only) Enable compilation of C++ with
compatibility with cfront version 2.1.
--cfront_3.0 (pgcpp only) Enable compilation of C++ with
compatibility with cfront version 3.0.
--compress_names (pgcpp only) Create a precompiled header file with the
name filename.
--dependencies (see –M) (pgcpp only) Print makefile dependencies to stdout.
--dependencies_to_file filename (pgcpp only) Print makefile dependencies to file
filename.
--display_error_number (pgcpp only) Display the error message number in any
diagnostic messages that are generated.
--diag_error tag (pgcpp only) Override the normal error severity of the
specified diagnostic messages.
--diag_remark tag (pgcpp only) Override the normal error severity of the
specified diagnostic messages.
--diag_suppress tag (pgcpp only) Override the normal error severity of the
specified diagnostic messages.
--diag_warning tag (pgcpp only) Override the normal error severity of the
specified diagnostic messages.
-e (pgcpp only) Set the C++ front-end error limit to the
specified .
--[no_]exceptions (pgcpp only) Disable/enable exception handling
support. The default is ––exceptions
––gnu_extensions (pgcpp only) Allow GNU extensions like “include next”
which are required to compile Linux system header files.
--[no]llalign (pgcpp only) Do/don’t align longlong integers on
integer boundaries. The default is ––llalign.
–M Generate make dependence lists.
–MD Generate make dependence lists.PGI® User’s Guide
170
Option Description
–MD,filename (pgcpp only) Generate make dependence lists and print
them to file filename.
--optk_allow_dollar_in_id_chars (pgcpp only) Accept dollar signs in identifiers.
–P Stops after the preprocessing phase and saves the
preprocessed file in filename.i.
-+p (pgcpp only) Disallow all anachronistic constructs.
cfront option
--pch (pgcpp only) Automatically use and/or create a
precompiled header file.
--pch_dir directoryname (pgcpp only) The directory dirname in which to search
for and/or create a precompiled header file.
--[no_]pch_messages (pgcpp only) Enable/ disable the display of a message
indicating that a precompiled header file was created or
used.
--preinclude= (pgcpp only) Specify file to be included at the beginning
of compilation so you can set system-dependent macros,
types, and so on.
-suffix (see–P ) (pgcpp only) Use with –E, –F, or –P to save
intermediate file in a file with the specified suffix.
–t Control instantiation of template functions. EDG option
--use_pch filename (pgcpp only) Use a precompiled header file of the
specified name as part of the current compilation.
--[no_]using_std (pgcpp only) Enable/disable implicit use of the std
namespace when standard header files are included.
–X (pgcpp only) Allow $ in names.
Generic PGI Compiler Options
The following descriptions are for the PGI options. For easy reference, the options are arranged in alphabetical
order. For a list of options by tasks, refer to Chapter 2, “Using Command Line Options,” on page 15.
–#
Displays the invocations of the compiler, assembler and linker.
Default: The compiler does not display individual phase invocations.
Usage:The following command-line requests verbose invocation information.
$ pgf95 -# prog.f
Description: The –# option displays the invocations of the compiler, assembler and linker. These invocations
are command-lines created by the driver from your command-line input and the default value.Chapter 15. Command-Line Options Reference
171
Related options:–Minfo, –V, –v.
–###
Displays the invocations of the compiler, assembler and linker, but does not execute them.
Default: The compiler does not display individual phase invocations.
Usage:The following command-line requests verbose invocation information.
$ pgf95 -### myprog.f
Description: Use the –### option to display the invocations of the compiler, assembler and linker but not to
execute them. These invocations are command lines created by the compiler driver from the PGIRC files and
the command-line options.
Related options: –#, –dryrun, –Minfo, –V
–Bdynamic
Compiles for and links to the DLL version of the PGI runtime libraries.
Default: The compiler uses static libraries.
Usage:You can create the DLL obj1.dll and its import library obj1.lib using the following series of
commands:
% pgf95 -Bdynamic -c object1.f
% pgf95 -Mmakedll object1.obj -o obj1.dll
Then compile the main program using this command:
$ pgf95 -# prog.f
For a complete example, refer to Example 7.1, “Build a DLL: Fortran,” on page 82.
Description: Use this option to compile for and link to the DLL version of the PGI runtime libraries. This flag
is required when linking with any DLL built by the PGI compilers. This flag corresponds to the /MD flag used
by Microsoft’s cl compilers.
Note
On Windows, -Bdynamic must be used for both compiling and linking.
When you use the PGI compiler flag –Bdynamic to create an executable that links to the DLL form of the
runtime, the executable built is smaller than one built without –Bdynamic. The PGI runtime DLLs, however,
must be available on the system where the executable is run. The –Bdynamic flag must be used when an
executable is linked against a DLL built by the PGI compilers.
Related options:–Bstatic, –Mdll
–Bstatic
Compiles for and links to the static version of the PGI runtime libraries.PGI® User’s Guide
172
Default: The compiler uses static libraries.
Usage:The following command line explicitly compiles for and links to the static version of the PGI runtime
libraries:
% pgf95 -Bstatic -c object1.f
Description: You can use this option to explicitly compile for and link to the static version of the PGI runtime
libraries.
Note
On Windows, -Bstatic must be used for both compiling and linking.
For more information on using static libraries on Windows, refer to “Creating and Using Static Libraries on
Windows,” on page 79.
Related options:–Bdynamic, –Mdll
–byteswapio
Swaps the byte-order of data in unformatted Fortran data files on input/output.
Default: The compiler does not byte-swap data on input/output.
Usage: The following command-line requests that byte-swapping be performed on input/output.
$ pgf95 -byteswapio myprog.f
Description: Use the –byteswapio option to swap the byte-order of data in unformatted Fortran data files
on input/output. When this option is used, the order of bytes is swapped in both the data and record control
words; the latter occurs in unformatted sequential files.
You can use option to convert big-endian format data files produced by most RISC workstations and high-end
servers to the little-endian format used on x86 or x64 systems on the fly during file reads/writes.
This option assumes that the record layouts of unformatted sequential access and direct access files are the
same on the systems. It further assumes that the IEEE representation is used for floating-point numbers. In
particular, the format of unformatted data files produced by PGI Fortran compilers is identical to the format
used on Sun and SGI workstations; this format allows you to read and write unformatted Fortran data files
produced on those platforms from a program compiled for an x86 or x64 platform using the –byteswapio
option.
Related options:
–C
Enables array bounds checking.
Default: The compiler does not enable array bounds checking.
Usage: In this example, the compiler instruments the executable produced from myprog.f to perform array
bounds checking at runtime:Chapter 15. Command-Line Options Reference
173
$ pgf95 -C myprog.f
Description: Use this option to enable array bounds checking. If an array is an assumed size array, the
bounds checking only applies to the lower bound. If an array bounds violation occurs during execution, an
error message describing the error is printed and the program terminates. The text of the error message
includes the name of the array, the location where the error occurred (the source file and the line number in
the source), and information about the out of bounds subscript (its value, its lower and upper bounds, and its
dimension).
Related options: –Mbounds.
–c
Halts the compilation process after the assembling phase and writes the object code to a file.
Default: The compiler produces an executable file (does not use the –c option).
Usage: In this example, the compiler produces the object file myprog.o in the current directory.
$ pgf95 -c myprog.f
Description: Use the –c option to halt the compilation process after the assembling phase and write the
object code to a file. If the input file is filename.f, the output file is filename.o.
Related options: –E, –Mkeepasm, –o, and –S.
–d
Prints additional information from the preprocessor.
Default:
Syntax:
-d[D|I|M|N]
-dD
Print macros and values from source files.
-dI
Print include file names.
-dM
Print macros and values, including predefined and command-line macros.
-dN
Print macro names from source files.
Usage: In the following example, the compiler prints macro names from the source file.
$ pgf95 -dN myprog.f
Description: Use the -d option to print additional information from the preprocessor.PGI® User’s Guide
174
Related options: –E, –D, –U.
–D
Creates a preprocessor macro with a given value.
Note
You can use the –D option more than once on a compiler command line. The number of active macro
definitions is limited only by available memory.
Syntax:
-Dname[=value]
Where name is the symbolic name and value is either an integer value or a character string.
Default: If you define a macro name without specifying a value, the preprocessor assigns the string 1 to the
macro name.
Usage: In the following example, the macro PATHLENGTH has the value 256 until a subsequent compilation. If
the –D option is not used, PATHLENGTH is set to 128.
$ pgf95 -DPATHLENGTH=256 myprog.F
The source text in myprog.F is this:
#ifndef PATHLENGTH
#define PATHLENGTH 128
#endif
SUBROUTINE SUB
CHARACTER*PATHLENGTH path
...
END
Use the –D option to create a preprocessor macro with a given value. The value must be either an integer or a
character string.
You can use macros with conditional compilation to select source text during preprocessing. A macro defined
in the compiler invocation remains in effect for each module on the command line, unless you remove the
macro with an #undef preprocessor directive or with the –U option. The compiler processes all of the –U
options in a command line after processing the –D options.
Related options: –U
–dryrun
Displays the invocations of the compiler, assembler, and linker but does not execute them.
Default: The compiler does not display individual phase invocations.
Usage: The following command-line requests verbose invocation information.
$ pgf95 -dryrun myprog.fChapter 15. Command-Line Options Reference
175
Description: Use the –dryrun option to display the invocations of the compiler, assembler, and linker but not
have them executed. These invocations are command lines created by the compiler driver from the PGIRC file
and the command-line supplied with –dryrun.
Related options: –Minfo, –V, –###
–E
Halts the compilation process after the preprocessing phase and displays the preprocessed output on the
standard output.
Default: The compiler produces an executable file.
Usage: In the following example the compiler displays the preprocessed myprog.f on the standard output.
$ pgf95 -E myprog.f
Description: Use the –E option to halt the compilation process after the preprocessing phase and display the
preprocessed output on the standard output.
Related options: –C, –c, –Mkeepasm, –o, –F, –S.
–F
Stops compilation after the preprocessing phase.
Default: The compiler produces an executable file.
Usage: In the following example the compiler produces the preprocessed file myprog.f in the current
directory.
$ pgf95 -F myprog.F
Description: Use the –F option to halt the compilation process after preprocessing and write the
preprocessed output to a file. If the input file is filename.F, then the output file is filename.f.
Related options: –c,–E, –Mkeepasm, –o, –S
–fast
Enables vectorization with SEE instructions, cache alignment, and flushz for 64-bit targets.
Default: The compiler enables vectorization with SEE instructions, cache alignment, and flushz.
Usage: In the following example the compiler produces vector SEE code when targeting a 64-bit machine.
$ pgf95 -fast vadd.f95
Description: When you use this option, a generally optimal set of options is chosen for targets that support
SSE capability. In addition, the appropriate –tp option is automatically included to enable generation of code
optimized for the type of system on which compilation is performed. This option enables vectorization with SEE
instructions, cache alignment, and flushz.PGI® User’s Guide
176
Note
Auto-selection of the appropriate –tp option means that programs built using the –fastsse option on a
given system are not necessarily backward-compatible with older systems.
Note
C/C++ compilers enable –Mautoinline with –fast.
Related options: –nfast, –O, –Munroll, –Mnoframe, –Mscalarsse, –Mvect, –Mcache_align, –tp
–fastsse
Synonymous with –fast.
--flagcheck
Causes the compiler to check that flags are correct then exit.
Default: The compiler begins a compile without the additional step to first validate that flags are correct.
Usage: In the following example the compiler checks that flags are correct, and then exits.
$ pgf95 --flagcheck myprog.f
Description: Use this option to make the compiler check that flags are correct and then exit. If flags are all
correct then the compiler returns a zero status.
Related options:
–flags
Displays driver options on the standard output.
Default: The compiler does not display the driver options.
Usage: In the following example the user requests information about the known switches.
$ pgf95 -flags
Description: Use this option to display driver options on the standard output. When you use this option with
–v, in addition to the valid options, the compiler lists options that are recognized and ignored.
Related options: –#, –###, –v
–fpic
(Linux only) Generates position-independent code suitable for inclusion in shared object (dynamically linked
library) files.
Default: The compiler does not generate position-independent code.Chapter 15. Command-Line Options Reference
177
Usage: In the following example the resulting object file, myprog.o, can be used to generate a shared object.
$ pgf95 -fpic myprog.f
(Linux only) Use the -fpic option to generate position-independent code suitable for inclusion in shared
object (dynamically linked library) files.
Related options: –shared, –fPIC, –G, –R
–fPIC
(Linux only) Equivalent to –fpic. Provided for compatibility with other compilers.
–G
(Linux only) Instructs the linker to produce a shared object file.
Default: The compiler does not instruct the linker to produce a shared object file.
Usage: In the following example the linker produces a shared object file.
$ pgf95 -G myprog.f
Description: (Linux only) Use this option to pass information to the linker that instructs the linker to
produce a shared object file.
Related options: –fpic, –shared, –R
–g
Instructs the compiler to include symbolic debugging information in the object module.
Default: The compiler does not put debugging information into the object module.
Usage: In the following example, the object file a.out contains symbolic debugging information.
$ pgf95 -g myprog.f
Description: Use the –g option to instruct the compiler to include symbolic debugging information in the
object module. Debuggers, such as PGDBG, require symbolic debugging information in the object module to
display and manipulate program variables and source code.
If you specify the –g option on the command-line, the compiler sets the optimization level to –O0 (zero),
unless you specify the –O option. For more information on the interaction between the –g and –O options,
see the –O entry. Symbolic debugging may give confusing results if an optimization level other than zero is
selected.
Note
Including symbolic debugging information increases the size of the object module.
Related options:–OPGI® User’s Guide
178
–gopt
Instructs the compiler to include symbolic debugging information in the object file, and to generate optimized
code identical to that generated when –g is not specified.
Default: The compiler does not put debugging information into the object module.
Usage: In the following example, the object file a.out contains symbolic debugging information.
$ pgf95 -gopt myprog.f
Description: Using –g alters how optimized code is generated in ways that are intended to enable or
improve debugging of optimized code. The –gopt option instructs the compiler to include symbolic debugging
information in the object file, and to generate optimized code identical to that generated when –g is not
specified.
Related options:
–g77libs
(Linux only) Used on the link line, this option instructs the pgf95 driver to search the necessary g77 support
libraries to resolve references specific to g77 compiled program units.
Note
The g77 compiler must be installed on the system on which linking occurs in order for this option to
function correctly.
Default: The compiler does not search g77 support libraries to resolve references at link time.
Usage: The following command-line requests that g77 support libraries be searched at link time:
$ pgf95 -g77libs myprog.f g77_object.o
Description: (Linux only) Use the –g77libs option on the link line if you are linking g77-compiled program
units into a pgf95-compiled main program using the pgf95 driver. When this option is present, the pgf95 driver
searches the necessary g77 support libraries to resolve references specific to g77 compiled program units.
Related options:
–help
Used with no other options, –help displays options recognized by the driver on the standard output. When
used in combination with one or more additional options, usage information for those options is displayed to
standard output.
Default: The compiler does not display usage information.
Usage: In the following example, usage information for –Minline is printed to standard output.
$ pgcc -help -Minline
-Minline[=lib:||except:|Chapter 15. Command-Line Options Reference
179
name:|size:|levels:]
Enable function inlining
lib: Use extracted functions from extlib
Inline function func
except: Do not inline function func
name: Inline function func
size: Inline only functions smaller than n
levels: Inline n levels of functions
-Minline Inline all functions that were extracted
In the following example, usage information for –help shows how groups of options can be listed or examined
according to function
$ pgcc -help -help
-help[=groups|asm|debug|language|linker|opt|other|
overall|phase|prepro|suffix|switch|target|variable]
Show compiler switches
Description: Use the –help option to obtain information about available options and their syntax. You can use
–help in one of three ways:
• Use –help with no parameters to obtain a list of all the available options with a brief one-line description
of each.
• Add a parameter to –help to restrict the output to information about a specific option. The syntax for this
usage is this:
-help
• Add a parameter to –help to restrict the output to a specific set of options or to a building process. The
syntax for this usage is this:
-help=
The following table lists and describes the subgroups available with –help. –help=groups Gives available
groups for help.
Table 15.6. Subgroups for –help Option
Use this –help
option
To get this information...
–help=asm A list of options specific to the assembly phase.
–help=debug A list of options related to debug information generation.
–help=groups A list of available groups to use with the help option.
–help=language A list of language-specific options.
–help=linker A list of options specific to link phase.
–help=opt A list of options specific to optimization phase.
–help=other A list of other options, such as ansi conformance pointer aliasing for
C.
–help=overall A list of option generic to any compiler.PGI® User’s Guide
180
Use this –help
option
To get this information...
–help=phase A list of build process phases and to which compiler they apply.
–help=prepro A list of options specific to preprocessing phase.
–help=suffix A list of known file suffixes and to which phases they apply.
–help=switch A list of all known options, this is equivalent to usage of –help
without any parameter.
–help=target A list of options specific to target processor.
–help=variable A list of all variables and their current value. They can be redefined
on the command line using syntax VAR=VALUE.
For more examples of –help, refer to “Help with Command-line Options,” on page 16.
Related options: –#, –###, –show, –V, –flags
–I
Adds a directory to the search path for files that are included using either the INCLUDE statement or the
preprocessor directive #include.
Default: The compiler searches only certain directories for included files.
• For gcc-lib includes: /usr/lib64/gcc-lib
• For system includes: /usr/linclude
Syntax:
-Idirectory
Where directory is the name of the directory added to the standard search path for include files.
Usage: In the following example, the compiler first searches the directory mydir and then searches the
default directories for include files.
$ pgf95 -Imydir
Description: Adds a directory to the search path for files that are included using the INCLUDE statement or
the preprocessor directive #include. Use the –I option to add a directory to the list of where to search for the
included files. The compiler searches the directory specified by the –I option before the default directories.
The Fortran INCLUDE statement directs the compiler to begin reading from another file. The compiler uses two
rules to locate the file:
1. If the file name specified in the INCLUDE statement includes a path name, the compiler begins reading from
the file it specifies.
2. If no path name is provided in the INCLUDE statement, the compiler searches (in order):Chapter 15. Command-Line Options Reference
181
• Any directories specified using the –I option (in the order specified.)
• The directory containing the source file
• The current directory
For example, the compiler applies rule (1) to the following statements:
INCLUDE '/bob/include/file1'
(absolute path name)
INCLUDE '../../file1' (relative path name)
and rule (2) to this statement:
INCLUDE 'file1'
Related options: –Mnostdinc
–i2, –i4 and –i8
Treat INTEGER and LOGICAL variables as either two, four, or eight bytes.
Default: The compiler treats INTERGER and LOGICAL variables as four bytes.
Usage: In the following example using the i8 switch causes the integer variables to be treated as 64 bits.
$ pgf95 -I8 int.f
int.f is a function similar to this:
int.f
print *, “Integer size:”, bit_size(i)
end
Description: Use this option to treat INTEGER and LOGICAL variables as either two, four, or eight bytes.
INTEGER*8 values not only occupy 8 bytes of storage, but operations use 64 bits, instead of 32 bits.
Related options:
–K
Requests that the compiler provide special compilation semantics.
Default: The compiler does not provide special compilation semantics.
Syntax:
–K
Where flag is one of the following:
ieee Perform floating-point operations in strict conformance with the IEEE 754
standard. Some optimizations are disabled, and on some systems a more
accurate math library is linked if –Kieee is used during the link step.PGI® User’s Guide
182
noieee Default flag. Use the fastest available means to perform floating-point
operations, link in faster non-IEEE libraries if available, and disable
underflow traps.
PIC (Linux only) Generate position-independent code. Equivalent to –fpic.
Provided for compatibility with other compilers.
pic (Linux only) Generate position-independent code. Equivalent to –fpic.
Provided for compatibility with other compilers.
trap=option
[,option]...
Controls the behavior of the processor when floating-point exceptions occur.
Possible options include:
• fp
• align (ignored)
• inv
• denorm
• divz
• ovf
• unf
• inexact
Usage: In the following example, the compiler performs floating-point operations in strict conformance with
the IEEE 754 standard
$ pgf95 -Kieee myprog.f
Description: Use -K to instruct the compile to provide special compilation semantics. The default is
–Knoieee.
–Ktrap is only processed by the compilers when compiling main functions or programs. The options inv,
denorm, divz, ovf, unf, and inexact correspond to the processor’s exception mask bits: invalid operation,
denormalized operand, divide-by-zero, overflow, underflow, and precision, respectively. Normally, the
processor’s exception mask bits are on, meaning that floating-point exceptions are masked—the processor
recovers from the exceptions and continues. If a floating-point exception occurs and its corresponding mask
bit is off, or “unmasked”, execution terminates with an arithmetic exception (C's SIGFPE signal).
–Ktrap=fp is equivalent to –Ktrap=inv,divz,ovf.
Note
The PGI compilers do not support exception-free execution for–Ktrap=inexact. The purpose of
this hardware support is for those who have specific uses for its execution, along with the appropriate
signal handlers for handling exceptions it produces. It is not designed for normal floating point
operation code support.
Related options:Chapter 15. Command-Line Options Reference
183
--keeplnk
(Windows only.) Preserves the temporary file when the compiler generates a temporary indirect file for a long
linker command.
Usage: In the following example the compiler preserves each temporary file rather than deleting it.
$ pgf95 --keeplnk myprog.f
Description: If the compiler generates a temporary indirect file for a long linker command, use this option to
instruct the compiler to preserve the temporary file instead of deleting it.
Related options:
–L
Specifies a directory to search for libraries.
Note
Multiple –L options are valid. However, the position of multiple –L options is important relative to –l
options supplied.
Syntax:
-Ldirectory
Where directory is the name of the library directory.
Default: The compiler searches the standard library directory.
Usage: In the following example, the library directory is /lib and the linker links in the standard libraries
required by PGF95 from this directory.
$ pgf95 -L/lib myprog.f
In the following example, the library directory /lib is searched for the library file libx.a and both the
directories /lib and /libz are searched for liby.a.
$ pgf95 -L/lib -lx -L/libz -ly myprog.f
Use the –L option to specify a directory to search for libraries. Using –L allows you to add directories to the
search path for library files.
Related options:-l
–l
Instructs the linker to load the specified library. The linker searches in addition to the standard
libraries.
Note
The linker searches the libraries specified with –l in order of appearance before searching the
standard libraries.PGI® User’s Guide
184
Syntax:
-llibrary
Where library is the name of the library to search.
Usage: In the following example, if the standard library directory is /lib the linker loads the library /lib/
libmylib.a, in addition to the standard libraries.
$ pgf95 myprog.f -lmylib
Description: Use this option to instruct the linker to load the specified library. The compiler prepends the
characters lib to the library name and adds the .a extension following the library name. The linker searches
each library specifies before searching the standard libraries.
Related options:–L
–m
Displays a link map on the standard output.
Default: The compiler does display the link map and does not use the –m option.
Usage:When the following example is executed on Windows, pgf95 creates a link map in the file
myprog.map.
$ pgf95 -m myprog.f
Description: Use this option to display a link map.
• On Linux, the map is written to stdout.
• On Windows, the map is written to a .map file whose name depends on the executable. If the executable is
myprog.f, the map file is in myprog.map.
Related options: –c, –o, -s, –u
–M
Selects options for code generation. The options are divided into the following categories:
Code generation Fortran Language Controls Optimization
Environment C/C++ Language Controls Miscellaneous
Inlining
The following table lists and briefly describes the options alphabetically and includes a field showing the
category. For more details about the options as they relate to these categories, refer to “–M Options by
Category,” on page 219.Chapter 15. Command-Line Options Reference
185
Table 15.7. –M Options Summary
pgflag Description Category
allocatable=95|03 Controls whether to use Fortran 95 or Fortran 2003
semantics in allocatable array assignments.
Fortran Language
anno Annotate the assembly code with source code. Miscellaneous
[no]autoinline C/C++ when a function is declared with the inline
keyword, inline it at –O2 and above.
Inlining
[no]asmkeyword Specifies whether the compiler allows the asm
keyword in C/C++ source files (pgcc and pgcpp
only).
C/C++ Language
[no]backslash Determines how the backslash character is treated
in quoted strings (pgf77, pgf95, and pghpf only).
Fortran Language
[no]bounds Specifies whether array bounds checking is enabled
or disabled.
Miscellaneous
– –[no_]builtin Do/don’t compile with math subroutine builtin
support, which causes selected math library routines
to be inlined (pgcc and pgcpp only).
Optimization
byteswapio Swap byte-order (big-endian to little-endian or vice
versa) during I/O of Fortran unformatted data.
Miscellaneous
cache_align Where possible, align data objects of size greater
than or equal to 16 bytes on cache-line boundaries.
Optimization
chkfpstk Check for internal consistency of the x87 FP stack
in the prologue of a function and after returning
from a function or subroutine call (–tp px/p5/p6/
piii targets only).
Miscellaneous
chkptr Check for NULL pointers (pgf95 and pghpf only). Miscellaneous
chkstk Check the stack for available space upon entry to
and before the start of a parallel region. Useful when
many private variables are declared.
Miscellaneous
concur Enable auto-concurrentization of loops. Multiple
processors or cores will be used to execute
parallelizable loops.
Optimization
cpp Run the PGI cpp-like preprocessor without
performing subsequent compilation steps.
Miscellaneous
cray Force Cray Fortran (CF77) compatibility (pgf77,
pgf95, and pghpf only).
Optimization
[no]daz Do/don’t treat denormalized numbers as zero. Code Generation
[no]dclchk Determines whether all program variables must be
declared (pgf77, pgf95, and pghpf only).
Fortran LanguagePGI® User’s Guide
186
pgflag Description Category
[no]defaultunit Determines how the asterisk character (“*”) is
treated in relation to standard input and standard
output (regardless of the status of I/O units 5 and 6,
pgf77, pgf95, and pghpf only).
Fortran Language
[no]depchk Checks for potential data dependencies. Optimization
[no]dse Enables [disables] dead store elimination phase for
programs making extensive use of function inlining.
Optimization
[no]dlines Determines whether the compiler treats lines
containing the letter "D" in column one as
executable statements (pgf77, pgf95, and pghpf
only).
Fortran Language
dll Link with the DLL version of the runtime libraries
(Windows only).
Miscellaneous
dollar,char Specifies the character to which the compiler maps
the dollar sign code (pgf77, pgf95, and pghpf only).
Fortran Language
dwarf1 When used with –g, generate DWARF1 format debug
information.
Code Generation
dwarf2 When used with –g, generate DWARF2 format debug
information.
Code Generation
dwarf3 When used with –g, generate DWARF3 format debug
information.
Code Generation
extend Instructs the compiler to accept 132-column source
code; otherwise it accepts 72-column code (pgf77,
pgf95, and pghpf only).
Fortran Language
extract invokes the function extractor. Inlining
fcon Instructs the compiler to treat floating-point
constants as float data types (pgcc and pgcpp only).
C/C++ Language
fixed Instructs the compiler to assume F77-style fixed
format source code (pgf95 and pghpf only).
Fortran Language
[no]flushz Do/don’t set SSE flush-to-zero mode Code Generation
[no]fprelaxed[=option] Perform certain floating point intrinsic functions
using relaxed precision.
Optimization
free Instructs the compiler to assume F90-style free
format source code (pgf95 and pghpf only).
Fortran Language
func32 The compiler aligns all functions to 32-byte
boundaries.
Code Generation
gccbug[s] Matches behavior of certain gcc bugs MiscellaneousChapter 15. Command-Line Options Reference
187
pgflag Description Category
noi4 Determines how the compiler treats INTEGER
variables (pgf77, pgf95, and pghpf only).
Optimization
info Prints informational messages regarding
optimization and code generation to standard output
as compilation proceeds.
Miscellaneous
inform Specifies the minimum level of error severity that the
compiler displays.
Miscellaneous
inline Invokes the function inliner. Inlining
[no]ipa Invokes inter-procedural analysis and optimization. Optimization
[no]iomutex Determines whether critical sections are generated
around Fortran I/O calls (pgf77, pgf95, and pghpf
only).
Fortran Language
keepasm Instructs the compiler to keep the assembly file. Miscellaneous
[no]large_arrays Enables support for 64-bit indexing and single static
data objects of size larger than 2GB.
Code Generation
lfs Links in libraries that allow file I/O to files of size
larger than 2GB on 32-bit systems (32-bit Linux
only).
Environment
[no]lre Disable/enable loop-carried redundancy
elimination.
Optimization
list Specifies whether the compiler creates a listing file. Miscellaneous
makedll Generate a dynamic link library (DLL) (Windows
only).
Miscellaneous
makeimplib Passes the -def switch to the librarian without a
deffile, when used without –def:deffile.
Miscellaneous
mpi=option Link to MPI libraries: MPICH1, MPICH2, or
Microsoft MPI libraries
Code Generation
[no]loop32 Aligns/does not align innermost loops on 32 byte
boundaries with –tp barcelona
Code Generation
[no]movnt Force/disable generation of non-temporal moves
and prefetching.
Code Generation
neginfo Instructs the compiler to produce information on
why certain optimizations are not performed.
Miscellaneous
noframe Eliminates operations that set up a true stack frame
pointer for functions.
Optimization
nomain When the link step is called, don’t include the object
file that calls the Fortran main program (pgf77,
pgf95, and pghpf only).
Code GenerationPGI® User’s Guide
188
pgflag Description Category
noopenmp When used in combination with the –mp
option, causes the compiler to ignore OpenMP
parallelization directives or pragmas, but still
process SGI-style parallelization directives or
pragmas.
Miscellaneous
nopgdllmain Do not link the module containing the default
DllMain() into the DLL (Windows only).
Miscellaneous
norpath On Linux, do not add –rpath paths to the link line. Miscellaneous
nosgimp When used in combination with the –mp
option, causes the compiler to ignore SGI-style
parallelization directives or pragmas, but still
process OpenMP directives or pragmas.
Miscellaneous
[no]stddef Instructs the compiler to not recognize the standard
preprocessor macros.
Environment
nostdinc Instructs the compiler to not search the standard
location for include files.
Environment
nostdlib Instructs the linker to not link in the standard
libraries.
Environment
[no]onetrip Determines whether each DO loop executes at least
once (pgf77, pgf95, and pghpf only).
Language
novintr Disable idiom recognition and generation of calls to
optimized vector functions.
Optimization
pfi Instrument the generated code and link in
libraries for dynamic collection of profile and data
information at runtime.
Optimization
pfo Read a pgfi.out trace file and use the information to
enable or guide optimizations.
Optimization
[no]prefetch Enable/disable generation of prefetch instructions. Optimization
preprocess Perform cpp-like preprocessing on assembly
language and Fortran input source files.
Miscellaneous
prof Set profile options; function-level and line-level
profiling are supported.
Code Generation
[no]r8 Determines whether the compiler promotes REAL
variables and constants to DOUBLE PRECISION
(pgf77, pgf95, and pghpf only).
Optimization
[no]r8intrinsics Determines how the compiler treats the intrinsics
CMPLX and REAL (pgf77, pgf95, and pghpf only).
Optimization
[no]recursive Allocate (do not allocate) local variables on the
stack, this allows recursion. SAVEd, data-initialized,
Code GenerationChapter 15. Command-Line Options Reference
189
pgflag Description Category
or namelist members are always allocated statically,
regardless of the setting of this switch (pgf77, pgf95,
and pghpf only).
[no]reentrant Specifies whether the compiler avoids optimizations
that can prevent code from being reentrant.
Code Generation
[no]ref_externals Do/don’t force references to names appearing in
EXTERNAL statements (pgf77, pgf95, and pghpf
only).
Code Generation
safeptr Instructs the compiler to override data dependencies
between pointers and arrays (pgcc and pgcpp only).
Optimization
safe_lastval In the case where a scalar is used after a loop, but
is not defined on every iteration of the loop, the
compiler does not by default parallelize the loop.
However, this option tells the compiler it safe to
parallelize the loop. For a given loop, the last value
computed for all scalars make it safe to parallelize
the loop.
Code Generation
[no]save Determines whether the compiler assumes that all
local variables are subject to the SAVE statement
(pgf77, pgf95, and pghpf only).
Fortran Language
[no]scalarsse Do/don’t use SSE/SSE2 instructions to perform
scalar floating-point arithmetic.
Optimization
schar Specifies signed char for characters (pgcc and
pgcpp only - also see uchar).
C/C++ Language
[no]second_underscore Do/don’t add the second underscore to the name
of a Fortran global if its name already contains an
underscore (pgf77, pgf95, and pghpf only).
Code Generation
[no]signextend Do/don’t extend the sign bit, if it is set. Code Generation
[no]single Do/don’t convert float parameters to double
parameter characters (pgcc and pgcpp only).
C/C++ Language
[no]smart Do/don’t enable optional post-pass assembly
optimizer.
Optimization
[no]smartalloc[=huge|
huge:|hugebss]
Add a call to the routine mallopt in the main routine.
Supports large TLBs on Linux and Windows. Tip.
To be effective, this switch must be specified when
compiling the file containing the Fortran, C, or C++
main program.
Environment
standard Causes the compiler to flag source code that does
not conform to the ANSI standard (pgf77, pgf95, and
pghpf only).
Fortran LanguagePGI® User’s Guide
190
pgflag Description Category
[no]stride0 Do/do not generate alternate code for a loop that
contains an induction variable whose increment may
be zero (pgf77, pgf95, and pghpf only).
Code Generation
uchar Specifies unsigned char for characters (pgcc and
pgcpp only - also see schar).
C/C++ Language
unix Uses UNIX calling and naming conventions for
Fortran subprograms (pgf77, pgf95, and pghpf for
Win32 only).
Code Generation
[no]nounixlogical Determines whether logical .TRUE. and .FALSE. are
determined by non-zero (TRUE) and zero (FALSE)
values for unixlogical. With nounixlogical, the
default, -1 values are TRUE and 0 values are FALSE
(pgf77, pgf95, and pghpf only).
Fortran Language
[no]unroll Controls loop unrolling. Optimization
[no]upcase Determines whether the compiler allows uppercase
letters in identifiers (pgf77, pgf95, and pghpf only).
Fortran Language
varargs Forces Fortran program units to assume calls are to
C functions with a varargs type interface (pgf77 and
pgf95 only).
Code Generation
[no]vect Do/don’t invoke the code vectorizer. Optimization
–mcmodel=medium
(For use only on 64-bit Linux targets) Generates code for the medium memory model in the linux86-64
execution environment. Implies –Mlarge_arrays.
Default: The compiler generates code for the small memory model.
Usage: The following command line requests position independent code be generated, and the
–mcmodel=medium option be passed to the assembler and linker:
$ pgf95 -mcmodel=medium myprog.f
Description: The default small memory model of the linux86-64 environment limits the combined area for
a user’s object or executable to 1GB, with the Linux kernel managing usage of the second 1GB of address for
system routines, shared libraries, stacks, and so on. Programs are started at a fixed address, and the program
can use a single instruction to make most memory references.
The medium memory model allows for larger than 2GB data areas, or .bss sections. Program units compiled
using either –mcmodel=medium or –fpic require additional instructions to reference memory. The effect on
performance is a function of the data-use of the application. The –mcmodel=medium switch must be used at
both compile time and link time to create 64-bit executables. Program units compiled for the default small
memory model can be linked into medium memory model executables as long as they are compiled with
–fpic, or position-independent.Chapter 15. Command-Line Options Reference
191
The linux86-64 environment provides static libxxx.a archive libraries that are built with and without –fpic,
and dynamic libxxx.so shared object libraries that are compiled –fpic. The –mcmodel=medium link switch
implies the –fpic switch and will utilize the shared libraries by default. Similarly, the $PGI/linux86-64//
lib directory contains the libraries for building small memory model codes, and the $PGI/linux86-64//
libso directory contains shared libraries for building –mcmodel=medium and –fpic executables.
Note
–mcmodel=medium -fpic is not allowed to create shared libraries. However, you can create
static archive libraries (.a) that are –fpic.
Related options:–Mlarge_arrays
–module
Allows you to specify a particular directory in which generated intermediate .mod files should be placed.
Default: The compiler places .mod files in the current working directory, and searches only in the current
working directory for pre-compiled intermediate .mod files.
Usage: The following command line requests that any intermediate module file produced during compilation
of myprog.f be placed in the directory mymods; specifically, the file ./mymods/myprog.mod is used.
$ pgf95 -module mymods myprog.f
Description: Use the –module option to specify a particular directory in which generated intermediate .mod
files should be placed. If the –module option is present, and USE statements are present in a
compiled program unit, then is searched for .mod intermediate files prior to a search in the
default local directory.
Related options:
–mp[=align,[no]numa]
Instructs the compiler to interpret user-inserted OpenMP shared-memory parallel programming directives and
pragmas, and to generate an executable file which will utilize multiple processors in a shared-memory parallel
system.
Default: The compiler ignores user-inserted shared-memory parallel programming directives and pragmas.
Usage: The following command line requests processing of any shared-memory directives present in
myprog.f:
$ pgf95 -mp myprog.f
Description: Use the –mp option to instruct the compiler to interpret user-inserted OpenMP shared-memory
parallel programming directives and to generate an executable file which utilizes multiple processors in a
shared-memory parallel system.
The align sub-option forces loop iterations to be allocated to OpenMP processes using an algorithm that
maximizes alignment of vector sub-sections in loops that are both parallelized and vectorized for SSE. ThisPGI® User’s Guide
192
allocation can improve performance in program units that include many such loops. It can also result in loadbalancing problems that significantly decrease performance in program units with relatively short loops that
contain a large amount of work in each iteration. The numa suboption uses libnuma on systems where it is
available.
For a detailed description of this programming model and the associated directives and pragmas, refer to
Chapter 5, “Using OpenMP”.
Related options: –Mconcur and –Mvect
–nfast
A generally optimal set of options is chosen depending on the target system. In addition, the appropriate
–tp option is automatically included to enable generation of code optimized for the type of system on which
compilation is performed.
Note
Auto-selection of the appropriate –tp option means that programs built using the –fast option on a
given system are not necessarily backward-compatible with older systems.
Usage: In the following example, the compiler selects a generally optimal set of options for the target system.
$ pgf95 -nfast myprog.f
Description: Use this option to instruct the compiler to select a generally optimal set of options for the
target system. In addition, the appropriate –tp option is automatically included to enable generation of code
optimized for the type of system on which compilation is performed.
Related options: –O, –Munroll, –Mnoframe, –Mvect, –tp, –Mscalarsse
–noswitcherror
Issues warnings instead of errors for unknown switches. Ignores unknown command line switches after
printing an warning message.
Default: The compiler prints an error message and then halts.
Usage: In the following example, the compiler ignores unknown command line switches after printing an
warning message.
$ pgf95 -noswitcherror myprog.f
Description: Use this option to instruct the compiler to ignore unknown command line switches after printing
an warning message.
Tip
You can configure this behavior in the siterc file by adding: set NOSWITCHERROR=1.
Related options:None.Chapter 15. Command-Line Options Reference
193
–O
Invokes code optimization at the specified level.
Default: The compiler optimizes at level 2 (correct?)
Syntax:
–O [level]
Where level is an integer from 0 to 4.
Usage: In the following example, since no –O option is specified, the compiler sets the optimization to level 1.
$ pgf95 myprog.f
In the following example, since no optimization level is specified and a –O option is specified, the compiler
sets the optimization to level 2.
$ pgf95 -O myprog.f
Description: Use this option to invoke code optimization at the specified level - one of the following:
0
creates a basic block for each statement. Neither scheduling nor global optimization is done. To specify
this level, supply a 0 (zero) argument to the –O option.
1
schedules within basic blocks and performs some register allocations, but does no global optimization.
2
performs all level-1 optimizations, and also performs global scalar optimizations such as induction
variable elimination and loop invariant movement.
3
level-three specifies aggressive global optimization. This level performs all level-one and level-two
op-timizations and enables more aggressive hoisting and scalar replacement optimizations that may or
may not be profitable.
4
level-four performs all level-one, level-two, and level-three op-timizations and enables hoisting of guarded
invariant floating point expressions.
Table 15.8 shows the interaction between the –O option, –g option, –Mvect, and –Mconcur options.
Table 15.8. Optimization and –O, –g, –Mvect, and –Mconcur Options
Optimize Option Debug Option –M Option Optimization Level
none none none 1
none none –Mvect 2PGI® User’s Guide
194
Optimize Option Debug Option –M Option Optimization Level
none none –Mconcur 2
none –g none 0
–O none or –g none 2
–Olevel none or –g none level
–Olevel < 2 none or –g –Mvect 2
–Olevel < 2 none or –g –Mconcur 2
Unoptimized code compiled using the option –O0 can be significantly slower than code generated at
other optimization levels. Like the –Mvect option, the –Munroll option sets the optimization level to
level-2 if no –O or –g options are supplied. The –gopt option is recommended for generation of debug
information with optimized code. For more information on optimization, see Chapter 3, “Using Optimization
& Parallelization”.
Related options: –g, –M, –gopt
–o
Names the executable file. Use the –o option to specify the filename of the compiler object file. The final output
is the result of linking.
Syntax:
–o filename
Where filename is the name of the file for the compilation output. The filename must not have a .f extension.
Default: The compiler creates executable filenames as needed. If you do not specify the –o option, the default
filename is the linker output file a.out.
Usage: In the following example, the executable file is myprog instead of the default a.out.
$ pgf95 myprog.f -o myprog
Related options: –c, –E, –F, –S
–pc
Note
This option is available only for –tp px/p5/p6/piii targets.
Allows you to control the precision of operations performed using the x87 floating point unit, and their
representation on the x87 floating point stack.
Syntax:
–pc { 32 | 64 | 80 }Chapter 15. Command-Line Options Reference
195
Usage:
$ pgf95 -pc 64 myprog.c
Description: The x87 architecture implements a floating-point stack using 8 80-bit registers. Each register
uses bits 0-63 as the significant, bits 64-78 for the exponent, and bit 79 is the sign bit. This 80-bit real format
is the default format, called the extended format. When values are loaded into the floating point stack they are
automatically converted into extended real format. The precision of the floating point stack can be controlled,
however, by setting the precision control bits (bits 8 and 9) of the floating control word appropriately. In
this way, you can explicitly set the precision to standard IEEE double-precision using 64 bits, or to single
precision using 32 bits.
1
The default precision is system dependent. To alter the precision in a given program
unit, the main program must be compiled with the same -pc option. The command line option –pc val lets the
programmer set the compiler’s precision preference. Valid values for val are:
• 32 single precision
• 64 double precision
• 80 extended precision
Extended Precision Option – Operations performed exclusively on the floating-point stack using extended
precision, without storing into or loading from memory, can cause problems with accumulated values within
the extra 16 bits of extended precision values. This can lead to answers, when rounded, that do not match
expected results.
For example, if the argument to sin is the result of previous calculations performed on the floating-point stack,
then an 80-bit value used instead of a 64-bit value can result in slight discrepancies. Results can even change
sign due to the sin curve being too close to an x-intercept value when evaluated. To maintain consistency in
this case, you can assure that the compiler generates code that calls a function. According to the x86 ABI, a
function call must push its arguments on the stack (in this way memory is guaranteed to be accessed, even if
the argument is an actual constant.) Thus, even if the called function simply performs the inline expansion,
using the function call as a wrapper to sin has the effect of trimming the argument precision down to the
expected size. Using the –Mnobuiltin option on the command line for C accomplishes this task by resolving
all math routines in the library libm, performing a function call of necessity. The other method of generating
a function call for math routines, but one that may still produce the inline instructions, is by using the –Kieee
switch.
A second example illustrates the precision control problem using a section of code to determine machine
precision:
program find_precision
w = 1.0
100 w=w+w
y=w+1
z=y-w
if (z .gt. 0) goto 100
C now w is just big enough that |((w+1)-w)-1| >= 1
...
print*,w
1
According to Intel documentation, this only affects the x87 operations of add, subtract, multiply, divide, and square root. In particular, it does not
appear to affect the x87 transcendental instructions.PGI® User’s Guide
196
end
In this case, where the variables are implicitly real*4, operations are performed on the floating-point
stack where optimization removed unnecessary loads and stores from memory. The general case of copy
propagation being performed follows this pattern:
a = x
y = 2.0 + a
Instead of storing x into a, then loading a to perform the addition, the value of x can be left on the floatingpoint stack and added to 2.0. Thus, memory accesses in some cases can be avoided, leaving answers in
the extended real format. If copy propagation is disabled, stores of all left-hand sides will be performed
automatically and reloaded when needed. This will have the effect of rounding any results to their declared
sizes.
For the above program, w has a value of 1.8446744E+19 when executed using default (extended) precision.
If, however, –Kieee is set, the value becomes 1.6777216E+07 (single precision.) This difference is due
to the fact that –Kieee disables copy propagation, so all intermediate results are stored into memory, then
reloaded when needed. Copy propagation is only disabled for floating-point operations, not integer. With this
particular example, setting the –pc switch will also adjust the result.
The switch –Kieee also has the effect of making function calls to perform all transcendental operations.
Although the function still produces the x86 machine instruction for computation (unless in C the
–Mnobuiltin switch is set), arguments are passed on the stack, which results in a memory store and load.
Finally, –Kieee also disables reciprocal division for constant divisors. That is, for a/b with unknown a and
constant b, the expression is usually converted at compile time to a*(1/b), thus turning an expensive divide
into a relatively fast scalar multiplication. However, numerical discrepancies can occur when this optimization
is used.
Understanding and correctly using the –pc, –Mnobuiltin, and Kieee switches should enable you to
produce the desired and expected precision for calculations which utilize floating-point operations.
Related options:
–pg
(Linux only) Instructs the compiler to instrument the generated executable for gprof-style sample-based
profiling.
Usage: In the following example the program is compiled for profiling using pgdbg or gprof.
$ pgf95 -pg myprog.c
Default: The compiler does not instrument the generated executable for gprof-style profiling.
Description: Use this option to instruct the compiler to instrument the generated executable for gprof-style
sample-based profiling. You must use this option at both the compile and link steps. A gmon.out style trace
is generated when the resulting program is executed, and can be analyzed using gprof or pgprof.
–pgf77libs
Instructs the compiler to append PGF77 runtime libraries to the link line.Chapter 15. Command-Line Options Reference
197
Default: The compiler does not append the PGF77 runtime libraries to the link line.
Usage: In the following example a .c main program is linked with an object file compiled with pgf77.
$ pgcc main.c myf77.o -pgf77libs
Description: Use this option to instruct the compiler to append PGF77 runtime libraries to the link line.
Related options:–pgf90libs
–pgf90libs
Instructs the compiler to append PGF90/PGF95 runtime libraries to the link line.
Default: The compiler does not append the PGF90/PGF95 runtime libraries to the link line.
Usage: In the following example a .c main program is linked with an object file compiled with pgf95.
$ pgf95 main.c myf95.o -pgf90libs
Description: Use this option to instruct the compiler to append PGF90/PGF95 runtime libraries to the link
line.
Related options:-pgf77libs
–Q
Selects variations for compilation. There are four uses for the –Q option.
Usage: The following examples show the different –Q options.
$ pgf95 -Qdir /home/comp/new hello.f
$ pgf95 -Qoption ld,-s hello.f
$ pgf95 -Qpath /home/test hello.f
$ pgf95 -Qproduce .s hello.f
Description: Use this option to select variations for compilation. As illustrated in the Usage section, there are
four varieties for the –Q option.
The first variety, using the dir keyword, lets you supply a directory parameter that indicates the directory where
the compiler driver is located.
-Qdirdirectory
The second variety, using the option keyword, lets you supply the option opt to the program prog. The prog
parameter can be one of pgftn, as, or ld.
-Qoptionprog,opt
The third –Q variety, using the path keyword, lets you supply an additional pathname to the search path for the
compiler’s required .o files.
-QpathpathnamePGI® User’s Guide
198
The fourth –Q variety, using the produce keyword, lets you choose a stop-after location for the compilation
based on the supplied sourcetype parameter. Valid sourcetypes are: .i, .c, .s and .o, which respectively indicate
the stop-after locations: preprocessing, compiling, assembling, or linking.
-Qproducesourcetype
Related options: –p
–R
(Linux only) Instructs the linker to hard-code the pathname into the search path for generated
shared object (dynamically linked library) files.
Note
There cannot be a space between R and .
Usage: In the following example, at runtime the a.out executable searches the specified directory, in this case
/home./Joe/myso, for shared objects.
$ pgf95 -Rm/home/Joe/myso myprog.f
Description: Use this option to instruct the compiler to pass information to the linker to hard-code the
pathname into the search path for shared object (dynamically linked library) files.
Related options: –fpic, –shared, –G
–r
Linux only. Creates a relocatable object file.
Default: The compiler does not create a relocatable object file and does not use the –r option.
Usage: In this example, pgf95 creates a relocatable object file.
$ pgf95 -r myprog.f
Use this option to create a relocatable object file.
Related options: –c, –o, –s, –u
–r4 and –r8
Interprets DOUBLE PRECISION variables as REAL (–r4) or REAL variables as DOUBLE PRECISION (–r8).
Usage: In this example, the double precision variables are interpreted as REAL.
$ pgf95 -r4 myprog.f
Description: Interpret DOUBLE PRECISION variables as REAL (–r4) or REAL variables as DOUBLE
PRECISION (–r8).
Related options: –i2, –i4, –i8, –nor8Chapter 15. Command-Line Options Reference
199
–rc
Specifies the name of the driver startup configuration file. If the file or pathname supplied is not a full
pathname, the path for the configuration file loaded is relative to the $DRIVER path (the path of the currently
executing driver). If a full pathname is supplied, that file is used for the driver configuration file.
Syntax:
-rc [path] filename
Where path is either a relative pathname, relative to the value of $DRIVER, or a full pathname beginning with "/
". Filename is the driver configuration file.
Default: The driver uses the configuration file .pgirc.
Usage: In the following example, the file .pgf95rctest, relative to /usr/pgi/linux86/bin, the value of
$DRIVER, is the driver configuration file.
$ pgf95 -rc .pgf95rctest myprog.f
Description: Use this option to specify the name of the driver startup configuration file. If the file or
pathname supplied is not a full pathname, the path for the configuration file loaded is relative to the $DRIVER
path - the path of the currently executing driver. If a full pathname is supplied, that file is used for the driver
configuration file.
Related options: –show
–rpath
Linux only.
Syntax:
-rpath path
Speicifes the name of the dirver startip configuration file, where path is either a relative pathname, or a full
pathname beginning with "/".
Default: The driver uses the configuration file .pgirc.
Usage: In the following example, the file .pgf95rctest, relative to /usr/pgi/linux86/bin, the value
of $DRIVER, is the driver configuration file.
$ pgf95 -rc .pgf95rctest myprog.f
Description: Use this option to specify the name of the driver startup configuration file. If the file or
pathname supplied is not a full pathname, the path for the configuration file loaded is relative to the $DRIVER
path - the path of the currently executing driver. If a full pathname is supplied, that file is used for the driver
configuration file.
Related options: –show
–s
(Linux only) Strips the symbol-table information from the executable file.PGI® User’s Guide
200
Default: The compiler includes all symbol-table information and does not use the –s option.
Usage: In this example, pgf95 strips symbol-table information from the a.out. executable file.
$ pgf95 -s myprog.f
Description: Use this option to strip the symbol-table information from the executable.
Related options: –c, –o, –u
–S
Stops compilation after the compiling phase and writes the assembly-language output to a file.
Default: The compiler does not produce a .s file.
Usage: In this example, pgf95 produces the file myprog.s in the current directory.
$ pgf95 -S myprog.f
Description: Use this option to stop compilation after the compiling phase and then write the assemblylanguage output to a file. If the input file is filename.f, then the output file is filename.s.
Related options: –c, –E, –F, –Mkeepasm, –o
–shared
(Linux only) Instructs the compiler to pass information to the linker to produce a shared object (dynamically
linked library) file.
Default: The compiler does not pass information to the linker to produce a shared object file.
Usage: In the following example the compiler passes information to the linker to produce the shared object
file: myso.so.
$ pgf95 -shared myprog.f -o myso.so
Description: Use this option to instruct the compiler to pass information to the linker to produce a shared
object (dynamically linked library) file.
Related options: –fpic, –G, –R
–show
Produces driver help information describing the current driver configuration.
Default: The compiler does not show driver help information.
Usage: In the following example, the driver displays configuration information to the standard output after
processing the driver configuration file.
$ pgf95 -show myprog.f
Description: Use this option to produce driver help information describing the current driver configuration.Chapter 15. Command-Line Options Reference
201
Related options: –V, –v, –###, –help, –rc
–silent
Do not print warning messages.
Default: The compiler prints warning messages.
Usage: In the following example, the driver does not display warning messages.
$ pgf95 -silent myprog.f
Description: Use this option to suppress warning messages.
Related options: –v, –V, –w
–soname
(Linux only.) The compiler recognizes the –soname option and passes it through to the linker.
Default: The compiler does not recognize the –soname option.
Usage: In the following example, the driver passes the soname option and its argument through to the linker.
$ pgf95 -soname library.so myprog.f
Description: Use this option to instruct the compiler to recognize the –soname option and pass it through to
the linker.
Related options:
–stack
(Windows only.) Allows you to explicitly set stack properties for your program.
Default: If –stack is not specified, then the defaults are as followed:
Win32
Setting is -stack:2097152,2097152, which is approximately 2MB for reserved and committed bytes.
Win64
No default setting
Syntax:
-stack={ (reserved bytes)[,(committed bytes)] }{, [no]check }
Usage: The following example demonstrates how to reserve 524,288 stack bytes (512KB), commit 262,144
stack bytes for each routine (256KB), and disable the stack initialization code with the nocheck argument.
$ pgf95 -stack=524288,262144,nocheck myprog.f
Description: Use this option to explicitly set stack properties for your program. The –stack option takes one
or more arguments: (reserved bytes), (committed bytes), [no]check.PGI® User’s Guide
202
reserved bytes
Specifies the total stack bytes required in your program.
committed bytes
Specifies the number of stack bytes that the Operating System will allocate for each routine in your
program. This value must be less than or equal to the stack reserved bytes value.
Default for this argument is 4096 bytes
[no]check
Instructs the compiler to generate or not to generate stack initialization code upon entry of each routine.
Check is the default, so stack initialization code is generated.
Stack initialization code is required when a routine's stack exceeds the committed bytes size. When your
committed bytes is equal to the reserved bytes or equal to the stack bytes required for each routine, then
you can turn off the stack initialization code using the -stack=nocheck compiler option. If you do this, the
compiler assumes that you are specifying enough committed stack space; and therefore, your program does
not have to manage its own stack size.
For more information on determining the amount of stack required by your program, refer to –Mchkstk
compiler option, described in “–M Miscellaneous Controls”.
Note
-stack=(reserved bytes),(committed bytes) are linker options.
-stack=[no]check is a compiler option.
If you specify -stack=(reserved bytes),(committed bytes) on your compile line, it is
only used during the link step of your build. Similarly, –stack=[no]check can be specified on your
link line, but its only used during the compile step of your build.
Related options:–Mchkstk
–time
Print execution times for various compilation steps.
Default: The compiler does not print execution times for compilation steps.
Usage: In the following example, pgf95 prints the execution times for the various compilation steps.
$ pgf95 -time myprog.f
Description: Use this option to print execution times for various compilation steps.
Related options: –#
–tp [,target...]
Sets the target architecture.Chapter 15. Command-Line Options Reference
203
Default: The PGI compilers produce code specifically targeted to the type of processor on which the
compilation is performed. In particular, the default is to use all supported instructions wherever possible when
compiling on a given system.
The default style of code generation is auto-selected depending on the type of processor on which compilation
is performed. Further, the –tp x64 style of unified binary code generation is only enabled by an explicit –tp
x64 option.
Note
Executables created on a given system may not be usable on previous generation systems. (For
example, executables created on a Pentium 4 may fail to execute on a Pentium III or Pentium II.)
Usage: In the following example, pgf95 sets the target architecture to EM64T:
$ pgf95 -tp p7-64 myprog.f
Description: Use this option to set the target architecture. By default, the PGI compiler uses all supported
instructions wherever possible when compiling on a given system. As a result, executables created on a given
system may not be usable on previous generation systems. For example, executables created on a Pentium 4
may fail to execute on a Pentium III or Pentium II.
Processor-specific optimizations can be specified or limited explicitly by using the –tp option. Thus, it is
possible to create executables that are usable on previous generation systems. With the exception of k8-64, k8-
64e, p7-64, and x64, any of these sub-options are valid on any x86 or x64 processor-based system. The k8-64,
k8-64e, p7-64 and x64 options are valid only on x64 processor-based systems.
The –tp x64 option generates unified binary object and executable files, as described in the section called
“Using –tp to Generate a Unified Binary”.
The following list is the possible sub-options for –tp and the processors that each sub-option is intended to
target:
k8-32
generate 32-bit code for AMD Athlon64, AMD Opteron and compatible processors.
k8-64
generate 64-bit code for AMD Athlon64, AMD Opteron and compatible processors.
k8-64e
generate 64-bit code for AMD Opteron Revision E, AMD Turion, and compatible processors.
p6
generate 32-bit code for Pentium Pro/II/III and AthlonXP compatible processors.
p7
generate 32-bit code for Pentium 4 and compatible processors.
p7-64
generate 64-bit code for Intel P4/Xeon EM64T and compatible processors.
core2
generate 32-bit code for Intel Core 2 Duo and compatible processors.PGI® User’s Guide
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core2-64
generate 64-bit code for Intel Core 2 Duo EM64T and compatible processors.
piii
generate 32-bit code for Pentium III and compatible processors, including support for single-precision
vector code using SSE instructions.
px
generate 32-bit code that is usable on any x86 processor-based system.
x64
generate 64-bit unified binary code including full optimizations and support for both AMD and Intel x64
processors.
Refer to Table 2, “Processor Options,” on page xxvi for a concise list of the features of these processors that
distinguish them as separate targets when using the PGI compilers and tools.
Syntax for 64-bit targets:
-tp {k8-64 | k8-64e | p7-64 | core2-64 | x64}
Syntax for 32-bit targets:
-tp {k8-32 | p6 | p7 | core2 | piii | px}
Using –tp to Generate a Unified Binary
Different processors have differences, some subtle, in hardware features such as instruction sets and
cache size. The compilers make architecture-specific decisions about such things as instruction selection,
instruction scheduling, and vectorization. Any of these decisions can have significant effects on performance
and compatibility. PGI unified binaries provide a low-overhead means for a single program to run well on a
number of hardware platforms.
You can use the –tp option to produce PGI Unified Binary programs. The compilers generate, and combine
into one executable, multiple binary code streams, each optimized for a specific platform. At runtime, this one
executable senses the environment and dynamically selects the appropriate code stream.
The target processor switch, –tp, accepts a comma-separated list of 64-bit targets and will generate code
optimized for each listed target. For example, the following switch generates optimized code for three targets:
k8-64, p7-64, and core2-64.
Syntax for optimizing for multiple targets:
-tp k8-64,p7-64,core2-64
The –tp k8-64 and –tp k8-64e options result in generation of code supported on and optimized for AMD x64
processors, while the –tp p7-64 option results in generation of code that is supported on and optimized for
Intel x64 processors. Performance of k8-64 or k8-64e code executed on Intel x64 processors, or of p7-64
code executed on AMD x64 processors, can often be significantly less than that obtained with a native binary.
The special –tp x64 option is equivalent to –tp k8-64,p7-64. This switch produces PGI Unified Binary
programs containing code streams fully optimized and supported for both AMD64 and Intel EM64T
processors.Chapter 15. Command-Line Options Reference
205
For more information on unified binaries, refer to “Processor-Specific Optimization and the Unified Binary,”
on page 36.
Related options:
–u
Initializes the symbol-table with , which is undefined for the linker.
Default: The compiler does not use the –u option.
Syntax:
-usymbol
Where symbol is a symbolic name.
Usage: In this example, pgf95 initializes symbol-table with ,
$ pgf95 -utest myprog.f
Description: Use this option to initialize the symbol-table with , which is undefined for the linker.
An undefined symbol triggers loading of the first member of an archive library.
Related options: –c, –o, –s
–U
Undefines a preprocessor macro.
Syntax:
-Usymbol
Where symbol is a symbolic name.
Usage: The following examples undefine the macro test.
$ pgf95 -Utest myprog.F
$ pgf95 -Dtest -Utest myprog.F
Description: Use this option to undefine a preprocessor macro. You can also use the #undef pre-processor
directive to undefine macros.
Related options: –D,–Mnostddef.
–V[release_number]
Displays additional information, including version messages. Further, if a release_number is appended, the
compiler driver attempts to compile using the specified release instead of the default release.
Note
There can be no space between –V and release_number.PGI® User’s Guide
206
Default: The compiler does not display version information and uses the release specified by your path to
compile.
Usage: The following command-line shows the output using the –V option.
% pgf95 -V myprog.f
The following command-line causes PGF95 to compile using the 5.2 release instead of the default release.
% pgcc -V5.2 myprog.c
Description: Use this option to display additional information, including version messages or, if a
release_number is appended, to instruct the compiler driver to attempt to compile using the specified release
instead of the default release.
The specified release must be co-installed with the default release, and must have a release number greater
than or equal to 4.1, which was the first release that supported this functionality.
Related options: –Minfo, –v
–v
Displays the invocations of the compiler, assembler, and linker.
Default: The compiler does not display individual phase invocations.
Usage: In the following example you use –v to see the commands sent to compiler tools, assembler, and
linker.
$ pgf95 -v myprog.f90
Description: Use the –v option to display the invocations of the compiler, assembler, and linker. These
invocations are command lines created by the compiler driver from the files and the –W options you specify on
the compiler command-line.
Related options: –Minfo, –, V, –W
–W
Passes arguments to a specific phase.
Syntax:
-W{0 | a | l },option[,option...]
Note
You cannot have a space between the –W and the single-letter pass identifier, between the identifier
and the comma, or between the comma and the option.
0
(the number zero) specifies the compiler.Chapter 15. Command-Line Options Reference
207
a
specifies the assembler.
l
(lowercase letter l) specifies the linker.
option
is a string that is passed to and interpreted by the compiler, assembler or linker. Options separated by
commas are passed as separate command line arguments.
Usage: In the following example the linker loads the text segment at address 0xffc00000 and the data segment
at address 0xffe00000.
$ pgf95 -Wl,-k,-t,0xffc00000,-d,0xffe00000 myprog.f
Description: Use this option to pass arguments to a specific phase. You can use the –W option to specify
options for the assembler, compiler, or linker.
Note
A given PGI compiler command invokes the compiler driver, which parses the command-line, and
generates the appropriate commands for the compiler, assembler, and linker.
Related options:
–w
Do not print warning messages.
Default: The compiler prints warning messages.
Usage: In the following example no warning messages are printed.
$ pgf95 -w myprog.f
Description: Use the –w option to not print warning messages. Sometimes the compiler issues many warning
in which you may have no interest. You can use this option to not issue those warnings.
Related options:–silent
–Xs
Use legacy standard mode for C and C++.
Default:None.
Usage: In the following example the compiler uses legacy standard mode.
$ pgcc -XS myprog.c
Description: Use this option to use legacy standard mode for C and C++. This option implies -
alias=traditional.
Related options:-alias, –XtPGI® User’s Guide
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–Xt
Use legacy traditional mode for C and C++.
Default:None.
Usage: In the following example the compiler uses legacy traditional mode.
$ pgcc -XStmyprog.c
Description: Use this option to use legacy standard mode for C and C++. This option implies -
alias=traditional.
Related options:-alias, –Xs
C and C++ -specific Compiler Options
There are a large number of compiler options specific to the PGCC and PGC++ compilers, especially PGC++.
This section provides the details of several of these options, but is not exhaustive. For a complete list of
available options, including an exhaustive list of PGC++ options, use the –help command-line option. For
further detail on a given option, use –help and specify the option explicitly, as described in –help .
–A
(pgcpp only) Instructs the PGC++ compiler to accept code conforming to the proposed ANSI C++ standard,
issuing errors for non-conforming code.
Default: By default, the compiler accepts code conforming to the standard C++ Annotated Reference Manual.
Usage: The following command-line requests ANSI conforming C++.
$ pgcpp -A hello.cc
Description: Use this option to instruct the PGC++ compiler to accept code conforming to the proposed ANSI
C++ standard and to issues errors for non-conforming code.
Related options:–a, –b and +p.
–a
(pgcpp only) Instructs the PGC++ compiler to accept code conforming to the proposed ANSI C++ standard,
issuing warnings for non-conforming code.
Default: By default, the compiler accepts code conforming to the standard C++ Annotated Reference Manual.
Usage: The following command-line requests ANSI conforming C++, issuing warnings for non-conforming
code.
$ pgcpp -a hello.cc
Description: Use this option to instruct the PGC++ compiler to accept code conforming to the proposed ANSI
C++ standard and to issues warnings for non-conforming code.Chapter 15. Command-Line Options Reference
209
Related options:–A, –b and +p.
–alias
select optimizations based on type-based pointer alias rules in C and C++.
Syntax:
-alias=[ansi|traditional]
Default:None
Usage: The following command-line enables optimizations.
$ pgcpp -alias=ansi hello.cc
Description: Use this option to select optimizations based on type-based pointer alias rules in C and C++.
ansi
Enable optimizations using ANSI C type-based pointer disambiguation
traditional
Disable type-based pointer disambiguation
Related options:
--[no_]alternative_tokens
(pgcpp only) Enables or disables recognition of alternative tokens. These are tokens that make it possible to
write C++ without the use of the comma (,) , [, ], #, &, ^, and characters. The alternative tokens include the
operator keywords (e.g., and, bitand, etc.) and digraphs. The default behavior is --no_alternative_tokens.
Default:. The default behavior is that the recognition of alternative tokens is disabled: --
no_alternative_tokens.
Usage: The following command-line enables alternative token recognition.
$ pgcpp --alternative_tokens hello.cc
(pgcpp only) Use this option to enable or disable recognition of alternative tokens. These tokens make it
possible to write C++ without the use of the comma (,), [, ], #, &, ^, and characters. The alternative tokens
include digraphs and the operator keywords, such as and, bitand, and so on. The default behavior is --
no_alternative_tokens.
Related options:
–B
(pgcc and pgcpp only) Enables use of C++ style comments starting with // in C program units.
Default: The PGCC ANSI and K&R C compiler does not allow C++ style comments.
Usage: In the following example the compiler accepts C++ style comments.PGI® User’s Guide
210
$ pgcc -B myprog.cc
Description: Use this option to enable use of C++ style comments starting with // in C program units.
Related options:
–b
(pgcpp only) Enables compilation of C++ with cfront 2.1 compatibility and acceptance of anachronisms.
Default: The compiler does not accept cfront language constructs that are not part of the C++ language
definition.
Usage: In the following example the compiler accepts cfront constructs.
$ pgcpp -b myprog.cc
Description: Use this option to enable compilation of C++ with cfront 2.1 compatibility. The compiler then
accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++
Language System (cfront release 2.1).
This option also enables acceptance of anachronisms.
Related options: ––cfront2.1, –b3 , ––cfront3.0, +p, –A
–b3
(pgcpp only) Enables compilation of C++ with cfront 3.0 compatibility and acceptance of anachronisms.
Default: The compiler does not accept cfront language constructs that are not part of the C++ language
definition.
Usage: In the following example, the compiler accepts cfront constructs.
$ pgcpp -b3 myprog.cc
Description: Use this option to enable compilation of C++ with cfront 3.0 compatibility. The compiler then
accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++
Language System (cfront release 3.0).
This option also enables acceptance of anachronisms.
Related options: ––cfront2.1, –b, ––cfront3.0, +p, –A
--[no_]bool
(pgcpp only) Enables or disables recognition of bool.
Default: The compile recognizes bool: --bool.
Usage: In the following example, the compiler does not recognize bool.
$ pgcpp --no_bool myprog.ccChapter 15. Command-Line Options Reference
211
Description: Use this option to enable or disable recognition of bool.
Related options:
– –[no_]builtin
Compile with or without math subroutine builtin support.
Default: The default is to compile with math subroutine support: ––built.
Usage: In the following example, the compiler does not build with math subroutine support.
$ pgcpp --no_builtin myprog.cc
Description: Use this option to enable or disable compiling with math subroutine builtin support. When you
compile with math subroutine builtin support, the selected math library routines are inlined.
Related options:
--cfront_2.1
(pgcpp only) Enables compilation of C++ with cfront 2.1 compatibility and acceptance of anachronisms.
Default: The compiler does not accept cfront language constructs that are not part of the C++ language
definition.
Usage: In the following example, the compiler accepts cfront constructs.
$ pgcpp --cfront_2.1 myprog.cc
Description: Use this option to enable compilation of C++ with cfront 2.1 compatibility. The compiler then
accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++
Language System (cfront release 2.1).
This option also enables acceptance of anachronisms.
Related options: –b, –b3, ––cfront3.0, +p, –A
--cfront_3.0
(pgcpp only) Enables compilation of C++ with cfront 3.0 compatibility and acceptance of anachronisms.
Default: The compiler does not accept cfront language constructs that are not part of the C++ language
definition.
Usage: In the following example, the compiler accepts cfront constructs.
$ pgcpp --cfront_3.0 myprog.cc
Description: Use this option to enable compilation of C++ with cfront 3.0 compatibility. The compiler then
accepts language constructs that, while not part of the C++ language definition, are accepted by the AT&T C++
Language System (cfront release 3.0).
This option also enables acceptance of anachronisms.PGI® User’s Guide
212
Related options: ––cfront2.1, –b, –b3, +p, –A
--compress_names
Compresses long function names in the file.
Default: The compiler does not compress names: --no_compress_names.
Usage: In the following example, the compiler compresses long function names.
$ pgcpp --ccompress_names yprog.cc
Description: Use this option to specify to compress long function names. Highly nested template parameters
can cause very long function names. These long names can cause problems for older assemblers. Users
encountering these problems should compileall C++ code, including library code with the switch --
compress_name. Libraries supplied by PGI work with --compress_names.
Related options:
--create_pch filename
(pgcpp only) If other conditions are satisfied, create a precompiled header file with the specified name.
Note
If --pch (automatic PCH mode) appears on the command line following this option, its effect is
erased.
Default: The compiler does not create a precompiled header file.
Usage: In the following example, the compiler creates a precompiled header file, hdr1.
$ pgcpp --create_pch hdr1 myprog.cc
Description: If other conditions are satisfied, use this option to create a precompiled header file with the
specified name.
Related options:
--diag_error tag
(pgcpp only) Overrides the normal error severity of the specified diagnostic messages.
Default: The compiler does not override normal error severity.
Description: Use this option to override the normal error severity of the specified diagnostic messages. The
message(s) may be specified using a mnemonic error tag or using an error number. ?
Related options:--diag_remark tag, --diag_suppress tag, --diag_warning tag, --display_error_number
--diag_remark tag
(pgcpp only) Overrides the normal error severity of the specified diagnostic messages.Chapter 15. Command-Line Options Reference
213
Default: The compiler does not override normal error severity.
Description: Use this option to override the normal error severity of the specified diagnostic messages. The
message(s) may be specified using a mnemonic error tag or using an error number.
Related options: --diag_error tag, --diag_suppress tag, --diag_warning tag, --display_error_number
--diag_suppress tag
(pgcpp only) Overrides the normal error severity of the specified diagnostic messages.
Default: The compiler does not override normal error severity.
Usage: In the following example, the compiler overrides the normal error severity ofthe specified diagnostic
messages..
$ pgcpp --diag_suppress error_tag prog.cc
Description: Use this option to override the normal error severity of the specified diagnostic messages. The
message(s) may be specified using a mnemonic error tag or using an error number.
Related options:--diag_error tag, --diag_remark tag, --diag_warning tag, --diag_error_number
--diag_warning tag
(pgcpp only) Overrides the normal error severity of the specified diagnostic messages.
Default: The compiler does not override normal error severity.
Usage: In the following example, the compiler overrides the normal error severity of the specified diagnostic
messages.
$ pgcpp --diag_suppress an_error_tag myprog.cc
Description: Use this option to override the normal error severity of the specified diagnostic messages. The
message(s) may be specified using a mnemonic error tag or using an error number.
Related options: --diag_error tag, --diag_remark tag, --diag_suppress tag, --diag_error_number
--display_error_number
(pgcpp only) Displays the error message number in any diagnostic messages that are generated. The option
may be used to determine the error number to be used when overriding the severity of a diagnostic message.
Default: The compiler does not display error message numbers for generated diagnostic messages.
Usage: In the following example, the compiler displays the error message number for any generated
diagnostic messages.PLEASE PROVIDE ONE
$ pgcpp --display_error_number myprog.cc
Description: Use this option to display the error message number in any diagnostic messages that are
generated. You can use this option to determine the error number to be used when overriding the severity of a
diagnostic message.PGI® User’s Guide
214
Related options: --diag_error tag, --diag_remark tag, --diag_suppress tag, --diag_warning tag
-e
(pgcpp only) Set the C++ front-end error limit to the specified .
--[no_]exceptions
(pgcpp only) Enables or disables exception handling support.
Default: The compiler provides exception handling support: --exceptions.
Usage: In the following example, the compiler does not provide exception handling support. PLEASE PROVIDE
ONE
$ pgcpp --no_exceptions myprog.cc
Description: Use this option to enable or disable exception handling support.
Related options:
––gnu_extensions
(pgcpp only) Allows GNU extensions.
Default: The compiler does not allow GNU extensions.
Usage: In the following example, the compiler allows GNU extensions.
$ pgcpp --gnu_extensions myprog.cc
Description: Use this option to allow GNU extensions, such as “include next”, which are required to compile
Linux system header files.
Related options:
--[no]llalign
(pgcpp only) Enables or disables alignment of long long integers on long long boundaries.
Default: The compiler aligns long long integers on long long boundaries: --llalign.
Usage: In the following example, the compiler does not align long long integers on long long boundaries.
$ pgcpp --nollalign myprog.cc
Description: Use this option to allow enable or disable alignment of long long integers on long long
boundaries.
Related options:
–M
Generates a list of make dependencies and prints them to stdout.Chapter 15. Command-Line Options Reference
215
Note
The compilation stops after the preprocessing phase.
Default: The compiler does not generate a list of make dependencies.
Usage: In the following example, the compiler generates a list of make dependencies.
$ pgcpp -M myprog.cc
Description: Use this option to generate a list of make dependencies and prints them to stdout.
Related options:–MD, –P, –suffix
–MD
Generates a list of make dependencies and prints them to a file.
Default: The compiler does not generate a list of make dependencies.
Usage: In the following example, the compiler generates a list of make dependencies and prints them to the
file myprog.d.
$ pgcpp -MD myprog.cc
Description: Use this option to generate a list of make dependencies and prints them to a file. The name of
the file is determined by the name of the file under compilation.dependencies_file.
Related options:–M, –P, –suffix
--optk_allow_dollar_in_id_chars
(pgcpp only) Accepts dollar signs ($) in identifiers.
Default: The compiler does not accept dollar signs ($) in identifiers.
Usage: In the following example, the compiler allows dollar signs ($) in identifiers.
$ pgcpp -optk_allow_dollar_in_id_chars myprog.cc
Description: Use this option to instruct the compiler to accept dollar signs ($) in identifiers.
–P
Halts the compilation process after preprocessing and writes the preprocessed output to a file.
Default: The compiler produces an executable file.
Usage: In the following example, the compiler produces the preprocessed file myprog.i in the current
directory.
$ pgcpp -P myprog.ccPGI® User’s Guide
216
Description: Use this option to halt the compilation process after preprocessing and write the preprocessed
output to a file. If the input file is filename.c or filename.cc., then the output file is filename.i.
Note
Use the –suffix option with this option to save the intermediate file in a file with the specified suffix.
Related options: –C,–c,–E, –Mkeepasm, –o, –S
-+p
(pgcpp only) Disallow all anachronistic constructs.
Default: The compiler disallows all anachronistic constructs.
Usage: In the following example, the compiler disallows all anachronistic constructs.
$ pgcpp -+p myprog.cc
Description: Use this option to disallow all anachronistic constructs.
Related options:
--pch
(pgcpp only) Automatically use and/or create a precompiled header file.
Note
If --use_pch or --create_pch (manual PCH mode) appears on the command line following this
option, this option has no effect.
Default: The compiler does not automatically use or create a precompiled header file.
Usage: In the following example, the compiler automatically uses a precompiled header file.
$ pgcpp --pch myprog.cc
Description: Use this option to automatically use and/or create a precompiled header file.
Related options:
--pch_dir directoryname
(pgcpp only) Specifies the directory in which to search for and/or create a precompiled header file.
The compiler searches your PATH for precompiled header files / use or create a precompiled header file.
Usage: In the following example, the compiler searches in the directory myhdrdir for a precompiled header
file.
$ pgcpp --pch_dir myhdrdir myprog.ccChapter 15. Command-Line Options Reference
217
Description: Use this option to specify the directory in which to search for and/or create a precompiled
header file. You may use this option with automatic PCH mode (--pch) or manual PCH mode (--create_pch or
--use_pch).
Related options:--create_pch, --pch, --use_pch
--[no_]pch_messages
(pgcpp only) Enables or disables the display of a message indicating that the current compilation used or
created a precompiled header file.
The compiler displays a message when it uses or creates a precompiled header file.
In the following example, no message is displayed when the precompiled header file located in myhdrdir is
used in the compilation.
$ pgcpp --pch_dir myhdrdir --no_pch_messages myprog.cc
Description: Use this option to enable or disable the display of a message indicating that the current
compilation used or created a precompiled header file.
Related options:--pch_dir,
--preinclude=
(pgcpp only) Specifies the name of a file to be included at the beginning of the compilation.
In the following example, the compiler includes the file incl_file.c at the beginning of the compilation.
me
$ pgcpp --preinclude=incl_file.c myprog.cc
Description: Use this option to specify the name of a file to be included at the beginning of the compilation.
For example, you can use this option to set system-dependent macros and types.
Related options:
--use_pch filename
(pgcpp only) Uses a precompiled header file of the specified name as part of the current compilation.
Note
If --pch (automatic PCH mode) appears on the command line following this option, its effect is
erased.
Default: The compiler does not use a precompiled header file.
In the following example, the compiler uses the precompiled header file, hdr1 as part of the current
compilation.
$ pgcpp --use_pch hdr1 myprog.ccPGI® User’s Guide
218
Use a precompiled header file of the specified name as part of the current compilation. If --pch (automatic
PCH mode) appears on the command line following this option, its effect is erased.
Related options:--create_pch, --pch_dir, --pch_messages
--[no_]using_std
(pgcpp only) Enables or disables implicit use of the std namespace when standard header files are included.
Default:The compiler uses std namespace when standard header files are included: --using_std.
Usage: The following command-line disables implicit use of the std namespace:
$ pgcpp --no_using_std hello.cc
Description: Use this option to enable or disable implicit use of the std namespace when standard header
files are included in the compilation.
Related options:
–t
(pgcpp only) Control instantiation of template functions.
–t [arg]
Default:No templates are instantiated.
Usage: In the following example, all templates are instantiated.
$ pgcpp -tall myprog.cc
Description: Use this option to control instantiation of template functions. The argument is one of the
following:
all
Instantiates all functions whether or not they are used.
local
Instantiates only the functions that are used in this compilation, and forces those functions to be local to
this compilation.
Note: This may cause multiple copies of local static variables. If this occurs, the program may not execute
correctly.
none
Instantiates no functions. (this is the default)
used
Instantiates only the functions that are used in this compilation.
Usage: In the following example, all templates are instantiated.
$ pgcppChapter 15. Command-Line Options Reference
219
-tall myprog.cc
–X
(pgcpp only) Generates cross-reference information and places output in the specified file.
Syntax:
–Xfoo
where foo is the specifies file for the cross reference information.
Default: The compiler does not generate cross-reference information.
Usage: In the following example, the compiler generates cross-reference information, placing it in the file:
xreffile.
$ pgcpp -Xxreffile myprog.cc
Description: Use this option to generate cross-reference information and place output in the specified file.
This is an EDG option.
Related options:
--zc_eh
(Linux only) Generates zero-overhead exceptionregions.
Default:The compiler does not to use --zc_eh but instead uses --sjlj_eh, which implements exception
handling with setjmp and longjmp.
Usage: The following command-line enables zero-overhead exception regions:
$ pgcpp --zc_eh ello.cc
Description: Use this option to generate zero-overhead exception regions. The --zc_eh option defers the
cost of exception handling until an exception is thrown. For a program with many exception regions and few
throws, this option may lead to improved run-time performance.
This option is compatible with C++ code that was compiled with previous version if PGI C++.
Note
The --zc_eh option is available only on newer Linux systems that supply the system unwind libraries in
libgcc_eh and on Windows.
Related options:
–M Options by Category
This section describes each of the options available with –M by the categories:
Code generation Fortran Language Controls OptimizationPGI® User’s Guide
220
C/C++ Language Controls Inlining Miscellaneous
Environment
For a complete alphabetical list of all the options, refer to “ –M Options Summary,” on page 185.
The following sections provide detailed descriptions of several, but not all, of the –M options. For a
complete alphabetical list of all the options, refer to “ –M Options Summary,” on page 185. These options
are grouped according to categories and are listed with exact syntax, defaults, and notes concerning similar or
related options. For the latest information and description of a given option, or to see all available options, use
the –help command-line option, described in“–help ,” on page 178.
–M Code Generation Controls
This section describes the –M options that control code generation.
Default: For arguments that you do not specify, the default code generation controls are these:
nodaz noreentrant nostride0
noflushz noref_externals signextend
norecursive nosecond_underscore
Related options: –D, –I, –L, –l, –U
Syntax:
Description and Related Options
–Mdaz
Set IEEE denormalized input values to zero; there is a performance benefit but misleading results can
occur, such as when dividing a small normalized number by a denormalized number. To take effect, this
option must be set for the main program.
–Mnodaz
Do not treat denormalized numbers as zero.To take effect, this option must be set for the main program.
–Mdwarf1
Generate DWARF1 format debug information; must be used in combination with –g.
–Mdwarf2
Generate DWARF2 format debug information; must be used in combination with –g.
–Mdwarf3
Generate DWARF3 format debug information; must be used in combination with –g.
–Mflushz
Set SSE flush-to-zero mode; if a floating-point underflow occurs, the value is set to zero.To take effect, this
option must be set for the main program.
–Mnoflushz
Do not set SSE flush-to-zero mode; generate underflows.To take effect, this option must be set for the main
program.Chapter 15. Command-Line Options Reference
221
–Mfunc32
Align functions on 32-byte boundaries.
–Mlarge_arrays
Enable support for 64-bit indexing and single static data objects larger than 2GB in size. This option
is default in the presence of –mcmodel=medium. Can be used separately together with the default
small memory model for certain 64-bit applications that manage their own memory space. For more
information, refer to Chapter 11, “Programming Considerations for 64-Bit Environments”.
–Mmpi=option
-Mmpi adds the include and library options to the compile and link commands necessary to build an MPI
application using MPI librariews installed with the PGI Cluister Development Kit (CDK).
On Linux, this option inserts -I$MPIDIR/include into the compile line and -L$MPIDIR/lib
into the link line. The specifies option determines whether to select MPICH-1 or MPICH-2 headers and
libraries. The base directories for MPICH-1 and MPICH-2 are set in localrc.
On Windows, this option inserts -I$MCCP_HOME/IncludeIncludeinto the compile line and -
L$CCP_HOME/lib into the link line.
The -Mmpi options are as specified:
• –Mmpi=mpich1 - Selects preconfigured MPICH-1 communication libraries.
• –Mmpi=mpich2 - Selects preconfigured MPICH-2 communication libraries.
• –Mmpi=msmpi - Select Microsoft MSMPI libraries.
Note
The user can set the environment variables MPIDIR and MPILIBNAME to override the default
values for the MPI directory and library name.
MPICH1 and MPICH2 apply only for PGI CDK Cluster Development Kit; MSMPI applies only on Microsoft
Compute Cluster systems.
For –Mmpi=msmpi to work, the CCP_HOME environment variable must be set. When the Microsoft
Compute Cluster SDK is installed, this variable is typically set to point to the MSMPI library directory.
–Mnolarge_arrays
Disable support for 64-bit indexing and single static data objects larger than 2GB in size. When placed
after –mcmodel=medium on the command line, disables use of 64-bit indexing for applications that have
no single data object larger than 2GB.
–Mnomain
Instructs the compiler not to include the object file that calls the Fortran main program as part of the link
step. This option is useful for linking programs in which the main program is written in C/C++ and one or
more subroutines are written in Fortran (pgf77, pgf95, and pghpf only).
–M[no]movnt
Instructs the compiler to generate nontemporal move and prefetch instructions even in cases where the
compiler cannot determine statically at compile-time that these instructions will be beneficial.PGI® User’s Guide
222
–Mprof[=option[,option,...]]
Set performance profiling options. Use of these options causes the resulting executable to create a
performance profile that can vbe viewed and analyzed with the PGPROF performance profiler. In the
descriptions that follow, PGI-style profiling implies compiler-generated source instrumentation. MPICHstyle profiling implies the use of instrumented wrappers for MPI library routines.
The option argument can be any of the following:
dwarf
Generate limited DWARF symbol information sufficient for most performance profilers.
func
Perform PGI-style function-level profiling.
hwcts
Generate a profile using event-based sampling of hardware counters via the PAPI interface. (linux86-
64 platforms only; PAPI must be installed).
lines
Perform PGI-style line-level profiling.
mpich1
Perform MPICH-style profiling for MPICH-1. Implied –Mmpi=mpich1. (Linux only).
mpich2
Perform MPICH-style profiling for MPICH-2. Implies –Mmpi=mpich2. (Linux with MPI support
licence privileges only.)
msmpi
Perform MPICH-style profiling for Microsoft MSMPI. Implies –Mmpi=msmpi. (Microsoft Compute
Cluster Server only ).
For -Mprof=msmpi to work, the CCP_HOME environment variable must be set. This variable is
typically set when the Microsoft Compute Cluster SDK is installed.
time
Generate a profile using time-based instruction-level statistical sampling. This is equivalent to -pg,
except that the profile is saved to a file names pgprof.out rather than gmon.out.
–Mrecursive
instructs the compiler to allow Fortran subprograms to be called recursively.
–Mnorecursive
Fortran subprograms may not be called recursively.
–Mref_externals
force references to names appearing in EXTERNAL statements (pgf77, pgf95, and pghpf only).
–Mnoref_externals
do not force references to names appearing in EXTERNAL statements (pgf77, pgf95, and pghpf only).
–Mreentrant
instructs the compiler to avoid optimizations that can prevent code from being reentrant.Chapter 15. Command-Line Options Reference
223
–Mnoreentrant
instructs the compiler not to avoid optimizations that can prevent code from being reentrant.
–Msecond_underscore
instructs the compiler to add a second underscore to the name of a Fortran global symbol if its name
already contains an underscore. This option is useful for maintaining compatibility with object code
compiled using g77, which uses this convention by default (pgf77, pgf95, and pghpf only).
–Mnosecond_underscore
instructs the compiler not to add a second underscore to the name of a Fortran global symbol if its name
already contains an underscore (pgf77, pgf95, and pghpf only).
–Msignextend
instructs the compiler to extend the sign bit that is set as a result of converting an object of one data type
to an object of a larger signed data type.
–Mnosignextend
instructs the compiler not to extend the sign bit that is set as the result of converting an object of one data
type to an object of a larger data type.
–Msafe_lastval
In the case where a scalar is used after a loop, but is not defined on every iteration of the loop, the
compiler does not by default parallelize the loop. However, this option tells the compiler it’s safe to
parallelize the loop. For a given loop the last value computed for all scalars make it safe to parallelize the
loop.
–Mstride0
instructs the compiler to inhibit certain optimizations and to allow for stride 0 array references. This
option may degrade performance and should only be used if zero-stride induction variables are possible.
–Mnostride0
instructs the compiler to perform certain optimizations and to disallow for stride 0 array references.
–Munix
use UNIX symbol and parameter passing conventions for Fortran subprograms (pgf77, pgf95, and pghpf
for Win32 only).
–Mvarargs
force Fortran program units to assume procedure calls are to C functions with a varargs-type interface
(pgf77 and pgf95 only).
–M C/C++ Language Controls
This section describes the –M options that affect C/C++ language interpretations by the PGI C and
C++ compilers. These options are only valid to the pgcc and pgcpp compiler drivers.
Default: For arguments that you do not specify, the defaults are as follows:
noasmkeyword nosingle
dollar,_ schar
Usage:PGI® User’s Guide
224
In this example, the compiler allows the asm keyword in the source file.
$ pgcc -Masmkeyword myprog.c
In the following example, the compiler maps the dollar sign to the dot character.
$ pgcc -Mdollar,. myprog.c
In the following example, the compiler treats floating-point constants as float values.
$ pgcc -Mfcon myprog.c
In the following example, the compiler does not convert float parameters to double parameters.
$ pgcc -Msingle myprog.c
Without –Muchar or with –Mschar, the variable ch is a signed character:
char ch;
signed char sch;
If –Muchar is specified on the command line:
$ pgcc -Muchar myprog.c
char ch above is equivalent to:
unsigned char ch;
Syntax:
Description and Related Options
–Masmkeyword
instructs the compiler to allow the asm keyword in C source files. The syntax of the asm statement is as
follows:
asm("statement");
Where statement is a legal assembly-language statement. The quote marks are required.
Note. The current default is to support gcc's extended asm, where the syntax of extended asm includes
asm strings. The –M[no]asmkeyword switch is useful only if the target device is a Pentium 3 or older cpu
type (–tp piii|p6|k7|athlon|athlonxp|px).
–Mnoasmkeyword
instructs the compiler not to allow the asm keyword in C source files. If you use this option and your
program includes the asm keyword, unresolved references will be generated
–Mdollar,char
char specifies the character to which the compiler maps the dollar sign ($). The PGCC compiler allows the
dollar sign in names; ANSI C does not allow the dollar sign in names.
–Mfcon
instructs the compiler to treat floating-point constants as float data types, instead of double data types. This
option can improve the performance of single-precision code.
–Mschar
specifies signed char characters. The compiler treats "plain" char declarations as signed char.Chapter 15. Command-Line Options Reference
225
–Msingle
do not to convert float parameters to double parameters in non-prototyped functions. This option can
result in faster code if your program uses only float parameters. However, since ANSI C specifies that
routines must convert float parameters to double parameters in non-prototyped functions, this option
results in non#ANSI conformant code.
–Mnosingle
instructs the compiler to convert float parameters to double parameters in non-prototyped functions.
–Muchar
instructs the compiler to treat "plain" char declarations as unsigned char.
–M Environment Controls
This section describes the –M options that control environments.
Default: For arguments that you do not specify, the default environment option depends on your
configuration.
Syntax:
Description and Related Options
–Mlfs
(32-bit Linux only) link in libraries that enable file I/O to files larger than 2GB (Large File Support).
–Mnostartup
instructs the linker not to link in the standard startup routine that contains the entry point (_start) for the
program.
Note
If you use the –Mnostartup option and do not supply an entry point, the linker issues the
following error message: Warning: cannot find entry symbol _start
–M[no]smartalloc[=huge|h[uge:|hugebss]
adds a call to the routine mallopt in the main routine. This option supports large TLBs on Linux and
Windows. This option must be used to compile the main routine to enable optimized malloc routines.
The option arguments can be any of the following:
huge
Link in the huge page runtime library
Enables large 2-megabyte pages to be allocated. The effect is to reduce the number of TLB entries
required to execute a program. This option is most effective on Barcelona and Core 2 systems; older
architectures do not have enough TLB entries for this option to be benefitical. By itself, the huge
suboption tries to allocate as many huge pages as required.
huge:
Link the huge page runtime library and allocate n huge pages. Use this suboption to limit the number
of huge pages allocated to n.PGI® User’s Guide
226
You can also limit the pages allocated by using the environment variable PGI_HUGE_PAGES.
hugebss
Puts the BSS section in huge pages; attempts to put a program's unititlaized data section into huge
pages.
Tip. To be effective, this switch must be specified when compiling the file containing the Fortran, C, or
C++ main program.
–M[no]stddef
instructs the compiler not to predefine any macros to the preprocessor when compiling a C program.
–Mnostdinc
instructs the compiler to not search the standard location for include files.
–Mnostdlib
instructs the linker not to link in the standard libraries libpgftnrtl.a, libm.a, libc.a and libpgc.a in the
library directory lib within the standard directory. You can link in your own library with the –l option or
specify a library directory with the –L option.
–M Fortran Language Controls
This section describes the –M options that affect Fortran language interpretations by the PGI Fortran
compilers. These options are valid only for the pghpf, pgf77 and pgf95 compiler drivers.
Default: For arguments that you do not specify, the defaults are as follows:
nobackslash noiomutex
nodclchk noonetrip
nodefaultunit nosave
nodlines nounixlogical
dollar,_ noupcase
Syntax:
Description and Related Options
–Mallocatable=95|03
controls whether Fortran 95 or Fortran 2003 semantics are used in allocatable array assignments. The
default behavior is to use Fortran 95 semantics; the 03 option instructs the compiler to use Fortran 2003
semantics.
–Mbackslash
the compiler treats the backslash as a normal character, and not as an escape character in quoted strings.
–Mnobackslash
the compiler recognizes a backslash as an escape character in quoted strings (in accordance with
standard C usage).
–Mdclchk
the compiler requires that all program variables be declared.Chapter 15. Command-Line Options Reference
227
–Mnodclchk
the compiler does not require that all program variables be declared.
–Mdefaultunit
the compiler treats "*" as a synonym for standard input for reading and standard output for writing.
–Mnodefaultunit
the compiler treats "*" as a synonym for unit 5 on input and unit 6 on output.
–Mdlines
the compiler treats lines containing "D" in column 1 as executable statements (ignoring the "D").
–Mnodlines
the compiler does not treat lines containing "D" in column 1 as executable statements (does not ignore
the "D").
–Mdollar,char
char specifies the character to which the compiler maps the dollar sign. The compiler allows the dollar
sign in names.
–Mextend
with –Mextend, the compiler accepts 132-column source code; otherwise it accepts 72-column code.
–Mfixed
with –Mfixed, the compiler assumes input source files are in FORTRAN 77-style fixed form format.
–Mfree
with –Mfree, the compiler assumes the input source files are in Fortran 90/95 freeform format.
–Miomutex
the compiler generates critical section calls around Fortran I/O statements.
–Mnoiomutex
the compiler does not generate critical section calls around Fortran I/O statements.
–Monetrip
the compiler forces each DO loop to execute at least once.
–Mnoonetrip
the compiler does not force each DO loop to execute at least once. This option is useful for programs
written for earlier versions of Fortran.
–Msave
the compiler assumes that all local variables are subject to the SAVE statement. Note that this may allow
older Fortran programs to run, but it can greatly reduce performance.
–Mnosave
the compiler does not assume that all local variables are subject to the SAVE statement.
–Mstandard
the compiler flags non-ANSI–conforming source code.
–Munixlogical
directs the compiler to treat logical values as true if the value is non-zero and false if the value is zero
(UNIX F77 convention.) When –Munixlogical is enabled, a logical value or test that is non-zero isPGI® User’s Guide
228
.TRUE., and a value or test that is zero is .FALSE.. In addition, the value of a logical expression is
guaranteed to be one (1) when the result is .TRUE..
–Mnounixlogical
Directs the compiler to use the VMS convention for logical values for true and false. Even values are true
and odd values are false.
–Mupcase
the compiler allows uppercase letters in identifiers. With –Mupcase, the identifiers "X" and "x" are
different, and keywords must be in lower case. This selection affects the linking process: if you compile
and link the same source code using –Mupcase on one occasion and –Mnoupcase on another, you may
get two different executables (depending on whether the source contains uppercase letters). The standard
libraries are compiled using the default –Mnoupcase.
–Mnoupcase
the compiler converts all identifiers to lower case. This selection affects the linking process: If you compile
and link the same source code using –Mupcase on one occasion and –Mnoupcase on another, you may
get two different executables (depending on whether the source contains uppercase letters). The standard
libraries are compiled using –Mnoupcase.
–M Inlining Controls
This section describes the –M options that control function inlining. Before looking at all the options,
let’s look at a couple examples.
Usage: In the following example, the compiler extracts functions that have 500 or fewer statements from the
source file myprog.f and saves them in the file extract.il.
$ pgf95 -Mextract=500 -oextract.il myprog.f
In the following example, the compiler inlines functions with fewer than approximately 100 statements in the
source file myprog.f and writes the executable code in the default output file a.out.
$ pgf95 -Minline=size:100 myprog.f
Related options: –o, –Mextract
Syntax:
Description and Related Options
–M[no]autoinline
instructs the compiler to inline a C/C++ function at –O2 and above when it is declared with the inline
keyword.
–Mextract[=option[,option,...]]
Extracts functions from the file indicated on the command line and creates or appends to the specified
extract directory where option can be any of:
name:func
instructs the extractor to extract function func from the file.
size:number
instructs the extractor to extract functions with number or fewer, statements from the file.Chapter 15. Command-Line Options Reference
229
lib:filename.ext
Use directory filename.ext as the extract directory (required in order to save and re-use inline
libraries).
If you specify both name and size, the compiler extracts functions that match func, or that have number or
fewer statements. For examples of extracting functions, see Chapter 4, “Using Function Inlining”.
–Minline[=option[,option,...]]
This passes options to the function inliner, where the option can be any of these:
except:func
instructs the inliner to inline all eligible functions except func, a function in the source text. Multiple
functions can be listed, comma-separated.
[name:]func
instructs the inliner to inline the function func. The func name should be a non-numeric string that
does not contain a period. You can also use a name: prefix followed by the function name. If name: is
specified, what follows is always the name of a function.
[lib:]filename.ext
instructs the inliner to inline the functions within the library file filename.ext. The compiler assumes
that a filename.ext option containing a period is a library file. Create the library file using the
–Mextract option. You can also use a lib: prefix followed by the library name. If lib: is specified, no
period is necessary in the library name. Functions from the specified library are inlined. If no library
is specified, functions are extracted from a temporary library created during an extract prepass.
levels:number
instructs the inliner to perform number levels of inlining. The default number is 1.
[no]reshape
instructs the inliner to allow (disallow)inlining in Fortran even when array shapes do not match. The
default is -Minline=noreshape, except with -Mconcur or -mp, where the default is -Minline=reshape.
[size:]number
instructs the inliner to inline functions with number or fewer statements. You can also use a size:
prefix followed by a number. If size: is specified, what follows is always taken as a number.
If you specify both func and number, the compiler inlines functions that match the function name or have
number or fewer statements. For examples of inlining functions, refer to Chapter 4, “Using Function
Inlining”.
–M Optimization Controls
This section describes the –M options that control optimization. Before looking at all the options,
let’s look at the defaults.
Default: For arguments that you do not specify, the default optimization control options are as follows:
depchk noipa nounroll nor8
i4 nolre novect nor8intrinsics
nofprelaxed noprefetchPGI® User’s Guide
230
Note
If you do not supply an option to –Mvect, the compiler uses defaults that are dependent upon the
target system.
Usage: In this example, the compiler invokes the vectorizer with use of packed SSE instructions enabled.
$ pgf95 -Mvect=sse -Mcache_align myprog.f
Related options: –g, –O
Syntax:
Description and Related Options
–Mcache_align
Align unconstrained objects of length greater than or equal to 16 bytes on cache-line boundaries. An
unconstrained object is a data object that is not a member of an aggregate structure or common block.
This option does not affect the alignment of allocatable or automatic arrays.
Note: To effect cache-line alignment of stack-based local variables, the main program or function must be
compiled with –Mcache_align.
–Mconcur[=option [,option,...]]
Instructs the compiler to enable auto-concurrentization of loops. If –Mconcur is specified, multiple
processors will be used to execute loops that the compiler determines to be parallelizable. Where option
is one of the following:
[no]altcode:n
Instructs the parallelizer to generate alternate serial code for parallelized loops. If altcode is specified
without arguments, the parallelizer determines an appropriate cutoff length and generates serial code
to be executed whenever the loop count is less than or equal to that length. If altcode:n is specified,
the serial altcode is executed whenever the loop count is less than or equal to n. If noaltcode is
specified, the parallelized version of the loop is always executed regardless of the loop count.
cncall
Calls in parallel loops are safe to parallelize. Loops containing calls are candidates for parallelization.
Also, no minimum loop count threshold must be satisfied before parallelization will occur, and last
values of scalars are assumed to be safe.
dist:block
Parallelize with block distribution (this is the default). Contiguous blocks of iterations of a
parallelizable loop are assigned to the available processors.
dist:cyclic
Parallelize with cyclic distribution. The outermost parallelizable loop in any loop nest is parallelized.
If a parallelized loop is innermost, its iterations are allocated to processors cyclically. For example,
if there are 3 processors executing a loop, processor 0 performs iterations 0, 3, 6, etc.; processor 1
performs iterations 1, 4, 7, etc.; and processor 2 performs iterations 2, 5, 8, etc.
[no]innermost
Enable parallelization of innermost loops. The default is to not parallelize innermost loops, since it is
usually not profitable on dual-core processors.Chapter 15. Command-Line Options Reference
231
noassoc
Disables parallelization of loops with reductions.
When linking, the –Mconcur switch must be specified or unresolved references will result. The NCPUS
environment variable controls how many processors or cores are used to execute parallelized loops.
Note
This option applies only on shared-memory multi-processor (SMP) or multi-core processorbased systems.
–Mcray[=option[,option,...]]
(pgf77 and pgf95 only) Force Cray Fortran (CF77) compatibility with respect to the listed options.
Possible values of option include:
pointer
for purposes of optimization, it is assumed that pointer-based variables do not overlay the storage of
any other variable.
–Mdepchk
instructs the compiler to assume unresolved data dependencies actually conflict.
–Mnodepchk
instructs the compiler to assume potential data dependencies do not conflict. However, if data
dependencies exist, this option can produce incorrect code.
–Mdse
Enables a dead store elimination phase that is useful for programs that rely on extensive use of inline
function calls for performance. This is disabled by default.
–Mnodse
(default) Disables the dead store elimination phase.
–M[no]fpapprox[=option]
Perform certain fp operations using low-precision approximation. By default -Mfpapprox is not used.
If -Mfpapprox is used without suboptions, it defaults to use approximate div, sqrt, and rsqrt. The available
suboptions are these:
div
Approximate floating point division
sqrt
Approximate floating point square root
rsqrt
Approximate floating point reciprocal square root
–M[no]fpmisalign
Instructs the compiler to allow (not allow) vector arithmetic instructions with memory operands that are
not aligned on 16-byte boundaries. The default is -Mnofpmisalign on all processors.PGI® User’s Guide
232
Note
Applicable only with one of these options: –tp barcelona or –tp barcelona-64
–Mfprelaxed[=option]
instructs the compiler to use relaxed precision in the calculation of some intrinsic functions. Can result in
improved performance at the expense of numerical accuracy.
The possible values for option are:
div
Perform divide using relaxed precision.
noorder
Perform reciprocal square root (1/sqrt) using relaxed precision.
order
Perform reciprocal square root (1/sqrt) using relaxed precision.
rsqrt
Perform reciprocal square root (1/sqrt) using relaxed precision.
sqrt
Perform square root with relaxed precision.
With no options, –Mfprelaxed generates relaxed precision code for those operations that generate a
significant performance improvement, depending on the target processor.
–Mnofprelaxed
(default) instructs the compiler not to use relaxed precision in the calculation of intrinsic functions.
–Mi4
(pgf77 and pgf95 only) the compiler treats INTEGER variables as INTEGER*4.
–Mipa=[, [,…]]
Pass options to the interprocedural analyzer. Note: –Mipa implies –O2, and the minimum optimization
level that can be specified in combination with –Mipa is –O2. For example, if you specify –Mipa –O1 on
the command line, the optimization level will automatically be elevated to –O2 by the compiler driver. It
is typical and recommended to use –Mipa=fast. Many of the following sub-options can be prefaced with
no, which reverses or disables the effect of the sub-option if it’s included in an aggregate sub-option like
–Mipa=fast. The choices of option are:
[no]align
recognize when targets of a pointer dummy are aligned; default is noalign.
[no]arg
remove arguments replaced by const, ptr; default is noarg.
[no]cg
generate call graph information for viewing using the pgicg command-line utility; default is nocg.
[no]const
perform interprocedural constant propagation; default is const.Chapter 15. Command-Line Options Reference
233
except:
used with inline to specify functions which should not be inlined; default is to inline all eligible
functions according to internally defined heuristics.
[[no]f90ptr
F90/F95 pointer disambiguation across calls; default is nof90ptr
fast
choose IPA options generally optimal for the target. Use –help to see the settings for –Mipa=fast on a
given target.
force
force all objects to re-compile regardless of whether IPA information has changed.
[no]globals
optimize references to global variables; default is noglobals.
inline[:n]
perform automatic function inlining. If the optional :n is provided, limit inlining to at most n levels.
IPA-based function inlining is performed from leaf routines upward.
ipofile
save IPA information in a .ipo file rather than incorporating it into the object file.
[no]keepobj
keep the optimized object files, using file name mangling, to reduce re-compile time in subsequent
builds default is keepobj.
[no]libc
optimize calls to certain standard C library routines.; default is nolibc.
[no]libinline
allow inlining of routines from libraries; implies –Mipa=inline; default is nolibinline.
[no]libopt
allow recompiling and optimization of routines from libraries using IPA information; default is
nolibopt.
[no]localarg
equivalent to arg plus externalization of local pointer targets; default is nolocalarg.
main:
specify a function to appear as a global entry point; may appear multiple times; disables linking.
[no]ptr
enable pointer disambiguation across procedure calls; default is noptr.
[no]pure
pure function detection; default is nopure.
required
return an error condition if IPA is inhibited for any reason, rather than the default behavior of linking
without IPA optimization.PGI® User’s Guide
234
[no]reshape
enables or disables Fortran inline with mismatched array shapes.
safe:[|]
declares that the named function, or all functions in the named library, are safe; a safe procedure
does not call back into the known procedures and does not change any known global variables.
Without –Mipa=safe, any unknown procedures will cause IPA to fail.
[no]safeall
declares that all unknown procedures are safe; see –Mipa=safe; default is nosafeall.
[no]shape
perform Fortran 90 array shape propagation; default is noshape.
summary
only collect IPA summary information when compiling; this prevents IPA optimization of this file, but
allows optimization for other files linked with this file.
[no]vestigial
remove uncalled (vestigial) functions; default is novestigial.
–M[no]loop32
Aligns or does not align innermost loops on 32 byte boundaries with –tp barcelona.
Small loops on barcelona may run fast if aligned on 32-byte boundaries; however, in practice, most
assemblers do not yet implement efficient padding causing some programs to run more slowly with this
default. Use -Mloop32 on systems with an assembler tuned for barcleona. The default is -Mnoloop32.
–Mlre[=array | assoc | noassoc]
Enables loop-carried redundancy elimination, an optimization that can reduce the number of arithmetic
operations and memory references in loops.
array
treat individual array element references as candidates for possible loop-carried redundancy
elimination. The default is to eliminate only redundant expressions involving two or more operands.
assoc
allow expression re-association; specifying this sub-option can increase opportunities for loop-carried
redundancy elimination but may alter numerical results.
noassoc
disallow expression re-association.
–Mnolre
Disables loop-carried redundancy elimination.
–Mnoframe
Eliminates operations that set up a true stack frame pointer for every function. With this option enabled,
you cannot perform a traceback on the generated code and you cannot access local variables.
–Mnoi4
(pgf77 and pgf95 only) the compiler treats INTEGER variables as INTEGER*2.Chapter 15. Command-Line Options Reference
235
–Mpfi
generate profile-feedback instrumentation; this includes extra code to collect run-time statistics and dump
them to a trace file for use in a subsequent compilation. –Mpfi must also appear when the program is
linked. When the resulting program is executed, a profile feedback trace file pgfi.out is generated in the
current working directory; see –Mpfo.
Note
compiling and linking with –Mpfi adds significant runtime overhead to almost any executable; you
should use executables compiled with –Mpfi only for execution of training runs.
–Mpfo
enable profile-feedback optimizations; requires the presence of a pgfi.out profile-feedback trace file in the
current working directory. See –Mpfi.
–Mprefetch[=option [,option...]]
enables generation of prefetch instructions on processors where they are supported. Possible values for
option include:
d:m
set the fetch-ahead distance for prefetch instructions to m cache lines.
n:p
set the maximum number of prefetch instructions to generate for a given loop to p.
nta
use the prefetchnta instruction.
plain
use the prefetch instruction (default).
t0
use the prefetcht0 instruction.
w
use the AMD-specific prefetchw instruction.
–Mnoprefetch
Disables generation of prefetch instructions.
–M[no]propcond
Enables or disables constant propagation from assertions derived from equality conditionals.
The default is enabled.
–Mr8
(pgf77, pgf95 and pghpf only) the compiler promotes REAL variables and constants to DOUBLE
PRECISION variables and constants, respectively. DOUBLE PRECISION elements are 8 bytes in length.
–Mnor8
(pgf77, pgf95 and pghpf only) the compiler does not promote REAL variables and constants to DOUBLE
PRECISION. REAL variables will be single precision (4 bytes in length).PGI® User’s Guide
236
–Mr8intrinsics
(pgf77, and pgf95 only) the compiler treats the intrinsics CMPLX and REAL as DCMPLX and DBLE,
respectively.
–Mnor8intrinsics
(pgf77, and pgf95 only) the compiler does not promote the intrinsics CMPLX and REAL to DCMPLX and
DBLE, respectively.
–Msafeptr[=option[,option,...]]
(pgcc and pgcpp only) instructs the C/C++ compiler to override data dependencies between pointers of a
given storage class. Possible values of option include:
all
assume all pointers and arrays are independent and safe for aggressive optimizations, and in
particular that no pointers or arrays overlap or conflict with each other.
arg
instructs the compiler that arrays and pointers are treated with the same copyin and copyout
semantics as Fortran dummy arguments.
global
instructs the compiler that global or external pointers and arrays do not overlap or conflict with each
other and are independent.
local/auto
instructs the compiler that local pointers and arrays do not overlap or conflict with each other and are
independent.
static
instructs the compiler that static pointers and arrays do not overlap or conflict with each other and
are independent.
–Mscalarsse
Use SSE/SSE2 instructions to perform scalar floating-point arithmetic (this option is valid only on –tp {p7 |
k8-32 | k8-64} targets).
–Mnoscalarsse
Do not use SSE/SSE2 instructions to perform scalar floating-point arithmetic; use x87 instructions instead
(this option is not valid in combination with the –tp k8-64 option).
–Msmart
instructs the compiler driver to invoke a post-pass assembly optimization utility.
–Mnosmart
instructs the compiler not to invoke an AMD64-specific post-pass assembly optimization utility.
–M[no]traceback
Adds debug information for runtime traceback for use with the environment variable $PGI_TERM. By
default, traceback is enabled for f77 and f90 and disabled for C and C++.
Setting setTRACEBACK=OFF; in siterc or .mypg*rc also disables default traceback.
Using ON instead of OFF enables default traceback.Chapter 15. Command-Line Options Reference
237
–Munroll[=option [,option...]]
invokes the loop unroller to executing multiple instances of the loop during each iteration. This also sets
the optimization level to 2 if the level is set to less than 2, or if no –O or –g options are supplied. The
option is one of the following:
c:m
instructs the compiler to completely unroll loops with a constant loop count less than or equal to m, a
supplied constant. If this value is not supplied, the m count is set to 4.
m:
instructs the compiler to unroll multi- block loops n times. This option is useful for loops that have
conditional statements. If n is not supplied, the default value is 4. The default setting is not to enable -
Munroll=m.
n:
instructs the compiler to unroll single-block loops n times, a loop that is not completely unrolled,
or has a non-constant loop count. If n is not supplied, the unroller computes the number of times a
candidate loop is unrolled.
–Mnounroll
instructs the compiler not to unroll loops.
-M[no]vect[=option [,option,...]]
(disable) enable the code vectorizer, where option is one of the following:
altcode
Instructs the vectorizer to generate alternate code (altcode) for vectorized loops when appropriate.
For each vectorized loop the compiler decides whether to generate altcode and what type or types
to generate, which may be any or all of: altcode without iteration peeling, altcode with non-temporal
stores and other data cache optimizations, and altcode based on array alignments calculated
dynamically at runtime. The compiler also determines suitable loop count and array alignment
conditions for executing the altcode. This option is enabled by default.
noaltcode
This disables alternate code generation for vectorized loops.
assoc
Instructs the vectorizer to enable certain associativity conversions that can change the results of a
computation due to roundoff error. A typical optimization is to change an arithmetic operation to
an arithmetic operation that is mathematically correct, but can be computationally different, due to
round-off error
noassoc
Instructs the vectorizer to disable associativity conversions.
cachesize:n
Instructs the vectorizer, when performing cache tiling optimizations, to assume a cache size of n. The
default is set using per-processor type, either using the –tp switch or auto-detected from the host
computer.
[no]gather
Vectorize loops containing indirect array references, such as this one:PGI® User’s Guide
238
sum = 0.d0
do k=d(j),d(j+1)-1
sum = sum + a(k)*b(c(k))
enddo
The default is -Mvect=gather.
[no]sizelimit
Generate vector code for all loops where possible regardless of the number of statements in the
loop. This overrides a heuristic in the vectorizer that ordinarily prevents vectorization of loops with a
number of statements that exceeds a certain threshold. The default is nosizelimit.
smallvect[:n]
Instructs the vectorizer to assume that the maximum vector length is less than or equal to n. The
vectorizer uses this information to eliminate generation of the stripmine loop for vectorized loops
wherever possible. If the size n is omitted, the default is 100.
Note: No space is allowed on either side of the colon (:).
sse
Instructs the vectorizer to search for vectorizable loops and, wherever possible, make use of SSE,
SSE2, and prefetch instructions.
–Mnovect
instructs the compiler not to perform vectorization; can be used to override a previous instance of –Mvect
on the command-line, in particular for cases where –Mvect is included in an aggregate option such as
–fastsse.
–Mnovintr
instructs the compiler not to perform idiom recognition or introduce calls to hand-optimized vector
functions.
–M Miscellaneous Controls
Default: For arguments that you do not specify, the default miscellaneous options are as follows:
inform nobounds nolist warn
Usage: In the following example, the compiler includes Fortran source code with the assembly code.
$ pgf95 -Manno -S myprog.f
In the following example, the compiler displays information about inlined functions with fewer than
approximately 20 source lines in the source file myprog.f.
$ pgf95 -Minfo=inline -Minline=20 myprog.f
In the following example, the assembler does not delete the assembly file myprog.s after the assembly pass.
$ pgf95 -Mkeepasm myprog.f
In the following example, the compiler creates the listing file myprog.lst.Chapter 15. Command-Line Options Reference
239
$ pgf95 -Mlist myprog.f
In the following example, array bounds checking is enabled.
$ pgf95 -Mbounds myprog.f
Related options: –m, –S, –V, –v
Syntax:
Description and Related Options
–Manno
annotate the generated assembly code with source code when either the –S or –Mkeepasm options are
used.
–Mbounds
enables array bounds checking. If an array is an assumed size array, the bounds checking only applies
to the lower bound. If an array bounds violation occurs during execution, an error message describing
the error is printed and the program terminates. The text of the error message includes the name of the
array, the location where the error occurred (the source file and the line number in the source), and
information about the out of bounds subscript (its value, its lower and upper bounds, and its dimension).
For example: PGFTN-F-Subscript out of range for array a (a.f: 2) subscript=3, lower bound=1, upper
bound=2, dimension=2
–Mnobounds
disables array bounds checking.
–Mbyteswapio
swap byte-order from big-endian to little-endian or vice versa upon input/output of Fortran unformatted
data files.
–Mchkfpstk (32-bit only)
instructs the compiler to check for internal consistency of the x87 floating-point stack in the prologue
of a function and after returning from a function or subroutine call. Floating-point stack corruption may
occur in many ways, one of which is Fortran code calling floating-point functions as subroutines (i.e.,
with the CALL statement). If the PGI_CONTINUE environment variable is set upon execution of a program
compiled with –Mchkfpstk, the stack will be automatically cleaned up and execution will continue. There
is a performance penalty associated with the stack cleanup. If PGI_CONTINUE is set to verbose, the stack
will be automatically cleaned up and execution will continue after printing of a warning message.
Note
This switch is only valid for 32-bit. On 64-bit it is ignored.
–Mchkptr
instructs the compiler to check for pointers that are de-referenced while initialized to NULL (pgf95 and
pghpf only).
–Mchkstk
instructs the compiler to check the stack for available space in the prologue of a function and before the
start of a parallel region. Prints a warning message and aborts the program gracefully if stack space is
insufficient. Useful when many local and private variables are declared in an OpenMP program.PGI® User’s Guide
240
If the user also sets the PGI_STACK_USAGE environment variable to any value, then the program
displays the stack space allocated and used after the program exits. For example, you might see something
similar the following message:
thread 0 stack: max 8180KB, used 48KB
This message indicates that the program used 48KB of a 8180KB allocated stack. For more information on
the PGI_STACK_USAGE, refer to“PGI_STACK_USAGE,” on page 97.
This information is useful when you want to explicitly set a reserved and committed stack size for your
programs, such as using the –stack option on Windows.
–Mcpp[=option [,option,...]]
run the PGI cpp-like preprocessor without execution of any subsequent compilation steps. This option is
useful for generating dependence information to be included in makefiles.
Note
Only one of the m, md, mm or mmd options can be present; if multiple of these options are listed,
the last one listed is accepted and the others are ignored.
The option is one or more of the following:
m
print makefile dependencies to stdout.
md
print makefile dependencies to filename.d, where filename is the root name of the input file being
processed.
mm
print makefile dependencies to stdout, ignoring system include files.
mmd
print makefile dependencies to filename.d, where filename is the root name of the input file being
processed, ignoring system include files.
[no]comment
(don’t) retain comments in output.
[suffix:]
use as the suffix of the output file containing makefile dependencies.
–Mdll
(Windows only) link with the DLL versions of the runtime libraries. This flag is required when linking with
any DLL built by any of The Portland Group compilers. This option implies –D_DLL, which defines the
preprocessor symbol _DLL.
–Mgccbug[s]
match the behavior of certain gcc bugs.
–Minfo[=option [,option,...]]
instructs the compiler to produce information on standard error, where option is one of the following:Chapter 15. Command-Line Options Reference
241
all
instructs the compiler to produce all available –Minfo information.
[no]file
instructs the compiler to print or not print source file names as they are compiled. The default is to
print the names, -Minfo=file.
inline
instructs the compiler to display information about extracted or inlined functions. This option is not
useful without either the –Mextract or –Minline option.
ipa
instructs the compiler to display information about interprocedural optimizations.
loop
instructs the compiler to display information about loops, such as information on vectorization.
opt
instructs the compiler to display information about optimization.
mp
instructs the compiler to display information about parallelization.
time
instructs the compiler to display compilation statistics.
unroll
instructs the compiler to display information about loop unrolling.
–Mneginfo[=option [,option,...]]
instructs the compiler to produce information on standard error, where option is one of the following:
all
instructs the compiler to produce all available information on why various optimizations are not
performed.
concur
instructs the compiler to produce all available information on why loops are not automatically
parallelized. In particular, if a loop is not parallelized due to potential data dependence, the
variable(s) that cause the potential dependence will be listed in the –Mneginfo messages.
loop
instructs the compiler to produce information on why memory hierarchy optimizations on loops are
not performed.
–Minform,level
instructs the compiler to display error messages at the specified and higher levels, where level is one of
the following:
fatal
instructs the compiler to display fatal error messages.
inform
instructs the compiler to display all error messages (inform, warn, severe and fatal).PGI® User’s Guide
242
severe
instructs the compiler to display severe and fatal error messages.
warn
instructs the compiler to display warning, severe and fatal error messages.
–Mkeepasm
instructs the compiler to keep the assembly file as compilation continues. Normally, the assembler
deletes this file when it is finished. The assembly file has the same filename as the source file, but with a .s
extension.
–Mlist
instructs the compiler to create a listing file. The listing file is filename.lst, where the name of the source
file is filename.f.
–Mmakedll
(Windows only) generate a dynamic link library (DLL).
–Mmakeimplib
(Windows only) when used without -def:deffile, passes the -def switch to the librarian without a deffile.
–Mnolist
the compiler does not create a listing file. This is the default.
–Mnoopenmp
when used in combination with the –mp option, causes the compiler to ignore OpenMP parallelization
directives or pragmas, but still process SGI-style parallelization directives or pragmas.
–Mnosgimp
when used in combination with the –mp option, causes the compiler to ignore SGI-style parallelization
directives or pragmas, but still process OpenMP parallelization directives or pragmas.
–Mnopgdllmain
(Windows only) do not link the module containing the default DllMain() into the DLL. This flag applies to
building DLLs with the PGF95 and PGHPF compilers. If you want to replace the default DllMain() routine
with a custom DllMain(), use this flag and add the object containing the custom DllMain() to the link line.
The latest version of the default DllMain() used by PGF95 and PGHPF is included in the Release Notes for
each release; the PGF95- and PGHPF-specific code in this routine must be incorporated into the custom
version of DllMain() to ensure the appropriate function of your DLL.
–Mnorpath
( Linux only) Do not add –rpath to the link line.
–Mpreprocess
perform cpp-like preprocessing on assembly and Fortran input source files.243
Chapter 16. OpenMP Reference
Information
The PGF77 and PGF95 Fortran compilers support the OpenMP Fortran Application Program Interface. The
PGCC ANSI C and C++ compilers support the OpenMP C/C++ Application Program Interface.
This chapter contains detailed descriptions of each of the OpenMP Fortran directives and C/C++ pragmas that
PGI supports. In addition, the section“Directive and Pragma Clauses,” on page 260 contains information
about the clauses associated with the directives and pragmas.
Parallelization Directives and Pragmas
Parallelization directives, as described in Chapter 5, “Using OpenMP”, are comments in a program that are
interpreted by the PGI Fortran compilers when the option -mp is specified on the command line. The form of a
parallelization directive is:
sentinel directive_name [clauses]
Parallelization pragmas are #pragma statements in a C or C++ program that are interpreted by the PGCC C and
C++ compilers when the option -mp is specified on the command line. The form of a parallelization pragma
is:
#pragma omp pragma_name [clauses]
The examples given with each section use the routines omp_get_num_threads() and
omp_get_thread_num(). For more information, refer to “Run-time Library Routines,” on page 55. They
return the number of threads currently in the team executing the parallel region and the thread number within
the team, respectively.
Note
Directives which are presented in pairs must be used in pairs.
This section describes the details of these directives and pragmas that were summarized in Chapter 5, “Using
OpenMP”. For each directive and pragma, this section describes the overall purpose, the syntax, the clauses
associated with it, the usage, and examples of how to use it.PGI® User’s Guide
244
ATOMIC
The OpenMP ATOMIC directive is semantically equivalent to a single statement in a CRITICAL...END CRITICAL
directive or the omp critical pragma.
!$OMP ATOMIC
Syntax:
!$OMP ATOMIC #pragma omp atomic
< C/C++ expression statement >
Usage:
The ATOMIC directive is semantically equivalent to enclosing the following single statement in a CRITICAL /
END CRITICAL directive pair. The omp atomic pragma is semantically equivalent to subjecting the following
single C/C++ expression statement to an omp critical pragma.
The statements must be one of the following forms:
For Directives:
x = x operator expr
x = expr operator x
x = intrinsic (x, expr)
x = intrinsic (expr, x)
For Pragmas:
x = expr
x++
++x
x--
--x
where x is a scalar variable of intrinsic type, expr is a scalar expression that does not reference x, intrinsic
is one of MAX, MIN, IAND, IOR, or IEOR, operator is one of +, *, -, /, .AND., .OR., .EQV., or .NEQV., and
is not overloaded and is one of +, *, -, /, &, ^, |, << or >>.
BARRIER
The OpenMP BARRIER directive defines a point in a program where each thread waits for all other threads to
arrive before continuing with program execution.
Syntax:
!$OMP BARRIER #pragma omp barrier
Usage:
There may be occasions in a parallel region, when it is necessary that all threads complete work to that
point before any thread is allowed to continue. The BARRIER directive or omp barrier pragma synchronizes
all threads at such a point in a program. Multiple barrier points are allowed within a parallel region. The
BARRIER directive and omp barrier pragma must either be executed by all threads executing the parallel
region or by none of them.Chapter 16. OpenMP Reference Information
245
CRITICAL ... END CRITICAL and omp critical
The CRITICAL ...END CRITICAL directive and omp critical pragma require a thread to wait until no other thread
is executing within a critical section.
Syntax:
!$OMP CRITICAL [(name)]
< Fortran code executed in body of
critical section >
!$OMP END CRITICAL [(name)]
#pragma omp critical [(name)]
< C/C++ structured block >
!$OMP CRITICAL [(name)]
< Fortran code executed in body of critical section >
!$OMP END CRITICAL [(name)]
Usage:
Within a parallel region, there may exist subregions of code that will not execute properly when executed by
multiple threads simultaneously. This issue is often due to a shared variable that is written and then read again.
The CRITICAL ... END CRITICAL directive pair and the omp critical pragma define a subsection of code within a
parallel region, referred to as a critical section, which is executed one thread at a time.
The first thread to arrive at a critical section is the first to execute the code within the section. The second
thread to arrive does not begin execution of statements in the critical section until the first thread exits the
critical section. Likewise, each of the remaining threads wait its turn to execute the statements in the critical
section.
You can use the optional name argument to identify the critical region. Names that identify critical regions have
external linkage and are in a name space separate from the name spaces used by labels, tags, members, and
ordinary identifiers. If a name argument appears on a CRITICAL directive, the same name must appear on the
END CRITICAL directive.
Note
Critical sections cannot be nested, and any such specifications are ignored. Branching into or out of a
critical section is illegal.
Example of Critical...End Critical directive:
PROGRAM CRITICAL_USE
REAL A(100,100),MX, LMX
INTEGER I, J
MX = -1.0
LMX = -1.0
CALL RANDOM_SEED()
CALL RANDOM_NUMBER(A)
!$OMP PARALLEL PRIVATE(I), FIRSTPRIVATE(LMX)
!$OMP DO
DO J=1,100
DO I=1,100
LMX = MAX(A(I,J),LMX)
ENDDO
ENDDOPGI® User’s Guide
246
!$OMP CRITICAL
MX = MAX(MX,LMX)
!$OMP END CRITICAL
!$OMP END PARALLEL
PRINT *,"MAX VALUE OF A IS ", MX
END
Example of omp critical pragma
#include
main(){
int a[100][100], mx=-1,lmx=-1, i, j;
for (j=0; j<100; j++)
for (i=0; i<100; i++)
a[i][j]=1+(int)(10.0*rand()/(RAND_MAX+1.0));
#pragma omp parallel private(i) firstprivate(lmx)
{
#pragma omp for
for (j=0; j<100; j++)
for (i=0; i<100; i++)
lmx = (lmx > a[i][j]) ? lmx : a[i][j];
#pragma omp critical
mx = (mx > lmx) ? mx : lmx;
}
printf ("max value of a is %d\n",mx);
}
This program could also be implemented without the critical region by declaring MX as a reduction variable
and performing the MAX calculation in the loop using MX directly rather than using LMX. Refer to “PARALLEL
... END PARALLEL and omp parallel ” and “DO ... END DO and omp for ” for more information on how to use
the REDUCTION clause on a parallel DO loop.
Example of omp critical pragma
#include
main(){
int a[100][100], mx=-1,
lmx=-1, i, j;
for (j=0; j<100; j++)
for (i=0; i<100; i++)
a[i][j]=1+(int)(10.0*rand()/(RAND_MAX+1.0));
#pragma omp parallel private(i) firstprivate(lmx)
{
#pragma omp for
for (j=0; j<100; j++)
for (i=0; i<100; i++)
lmx = (lmx > a[i][j]) ? lmx : a[i][j];
#pragma omp critical
mx = (mx > lmx) ? mx : lmx;
}
printf ("max value of a is %d\n",mx);
}
C$DOACROSS
The C$DOACROSS directive, while not part of the OpenMP standard, is supported for compatibility with
programs parallelized using legacy SGI-style directives.
Syntax:Chapter 16. OpenMP Reference Information
247
C$DOACROSS [ Clauses ]
< Fortran DO loop to be executed
in parallel >
#pragma omp parallel [clauses]
< C/C++ structured block >
Clauses:
[ {PRIVATE | LOCAL} (list) ]
[ {SHARED | SHARE} (list) ]
[ MP_SCHEDTYPE={SIMPLE | INTERLEAVE} ]
[ CHUNK= ]
[ IF (logical_expression) ]
Usage:
The C$DOACROSS directive has the effect of a combined parallel region and parallel DO loop applied to the
loop immediately following the directive. It is very similar to the OpenMP PARALLEL DO directive, but provides
for backward compatibility with codes parallelized for SGI systems prior to the OpenMP standardization effort.
The C$DOACROSS directive must not appear within a parallel region. It is a shorthand notation that tells the
compiler to parallelize the loop to which it applies, even though that loop is not contained within a parallel
region. While this syntax is more convenient, it should be noted that if multiple successive DO loops are to be
parallelized it is more efficient to define a single enclosing parallel region and parallelize each loop using the
OpenMP DO directive.
A variable declared PRIVATE or LOCAL to a C$DOACROSS loop is treated the same as a private variable in a
parallel region or DO (see above). A variable declared SHARED or SHARE to a C$DOACROSS loop is shared
among the threads, meaning that only 1 copy of the variable exists to be used and/or modified by all of the
threads. This is equivalent to the default status of a variable that is not listed as PRIVATE in a parallel region or
DO (this same default status is used in C$DOACROSS loops as well).
DO ... END DO and omp for
The OpenMP DO ...END DO directive and omp for pragma support parallel execution and the distribution of
loop iterations across available threads in a parallel region.
Syntax:
!$OMP DO [Clauses]
< Fortran DO loop to be executed in
parallel
!$OMP END DO [NOWAIT]
#pragma omp for [Clauses]
< C/C++ for loop to be executed in
parallel >
Clauses:
For Directives:
PRIVATE(list)
FIRSTPRIVATE(list)
LASTPRIVATE(list)
REDUCTION({operator | intrinsic } : list)
SCHEDULE (type [, chunk])
ORDERED
For Pragmas:
private(list)
firstprivate(list)
lastprivate(list)
reduction(operator: list)
schedule (kind[, chunk])
ordered
nowaitPGI® User’s Guide
248
Usage:
The real purpose of supporting parallel execution is the distribution of work across the available threads. The
DO ... END DO directive pair and the omp for pragma provide a convenient mechanism for the distribution of
loop iterations across the available threads in a parallel region.
While you can explicitly manage work distribution with constructs such as the following one, these constructs
are not in the form of directives or pragmas.
Examples:
For Directives:
IF (omp_get_thread_num() .EQ. 0)
THEN
...
ELSE IF (omp_get_thread_num() .EQ. 1)
THEN
...
ENDIF
For Pragmas:
if (omp_get_thread_num() == 0) {
...
}
else if (omp_get_thread_num() == 1) {
...
}t
Tips
Remember these items about clauses in the DO...END DO directives and omp for pragmas:
• Variables declared in a PRIVATE list are treated as private to each processor participating in parallel
execution of the loop, meaning that a separate copy of the variable exists on each processor.
• Variables declared in a FIRSTPRIVATE list are PRIVATE, and in addition are initialized from the original
object existing before the construct.
• Variables declared in a LASTPRIVATE list are PRIVATE, and in addition the thread that executes the
sequentially last iteration updates the version of the object that existed before the construct.
• The REDUCTION clause for the directive is described in “PARALLEL ... END PARALLEL and omp parallel ,”
on page 251 and the reduction clause for the pragma is described in“Directive and Pragma Clauses,” on
page 260.
• The SCHEDULE clause is explained in the following section.
• If ORDERED code blocks are contained in the dynamic extent of the DO directive, the ORDERED clause
must be present. For more information on ORDERED code blocks, refer to “ORDERED ”.
• If ordered code blocks are contained in the dynamic extent of the for directive, the ordered clause must be
present. See “ORDERED ,” on page 251 for more information on ordered code blocks.
• The DO ... END DO directive pair directs the compiler to distribute the iterative DO loop immediately
following the !$OMP DO directive across the threads available to the program. The DO loop is executed in
parallel by the team that was started by an enclosing parallel region. If the !$OMP END DO directive is not
specified, the !$OMP DO is assumed to end with the enclosed DO loop. DO ... END DO directive pairs may
not be nested. Branching into or out of a !$OMP DO loop is not supported.
• The omp for pragma directs the compiler to distribute the iterative for loop immediately following across
the threads available to the program. The for loop is executed in parallel by the team that was started by anChapter 16. OpenMP Reference Information
249
enclosing parallel region. Branching into or out of an omp for loop is not supported, and omp for pragmas
may not be nested.
• By default, there is an implicit barrier after the end of the parallel loop; the first thread to complete its
portion of the work waits until the other threads have finished their portion of work. If NOWAIT is specified,
the threads will not synchronize at the end of the parallel loop.
In addition to the preceding items, remember these items about !$OMP DO loops and omp for loops:
• The DO loop index variable is always private.
• The for loop index variable is always private and must be a signed integer.
• !$OMP DO loops and omp for loops must be executed by all threads participating in the parallel region or
none at all.
• The END DO directive is optional, but if it is present it must appear immediately after the end of the
enclosed DO loop.
• The for loop must be a structured block and its execution must not be terminated by break.
• Values of the loop control expressions and the chunk expressions must be the same for all threads
executing the loop.
Examples:
Example of Do...END DO directive
PROGRAM DO_USE
REAL A(1000), B(1000)
DO I=1,1000
B(I) = FLOAT(I)
ENDDO
!$OMP PARALLEL
!$OMP DO
DO I=1,1000
A(I) = SQRT(B(I));
ENDDO
...
!$OMP END PARALLEL
...
END
Example of omp for pragma
#include
#include
main(){
float a[1000], b[1000];
int i;
for (i=0; i<1000; i++)
b[i] = i;
#pragma omp parallel
{
#pragma omp for
for (i=0; i<1000; i++)
a[i] = sqrt(b[i]);
...
}
...
}
The SCHEDULE clause specifies how iterations of the DO or for loop are divided up between processors. For
more information on this clause, refer to “Schedule Clause,” on page 261.
FLUSH and omp flush pragma
The OpenMP FLUSH directive and omp flush pragma ensure that all processor-visible data items, or only those
specified in list when it’s present, are written back to memory at the point at which the directive appears.
Syntax:PGI® User’s Guide
250
!$OMP FLUSH [(list)] #pragma omp flush [(list)]
Usage:
The FLUSH directive ensures that all processor-visible data items, or only those specified in the list, when it is
present, are written back to memory at the point at which the directive or pragma appears.
MASTER ... END MASTER and omp master pragma
The MASTER....END MASTER directive and omp master pragma allow the user to designate code that must
execute on a master thread and that is skipped by other threads in the team of threads.
Syntax:
!$OMP MASTER
< Fortran code executed in body of
MASTER section >
!$OMP END MASTER
#pragma omp master
< C/C++ structured block >
Usage:
A master thread is a single thread of control that begins an OpenMP program and which is present for the
duration of the program. In a parallel region of code, there may be a sub-region of code that should execute
only on the master thread. Instead of ending the parallel region before this subregion and then starting it up
again after this subregion, the MASTER ... END MASTER directive pair or omp master pragma allows the user
to conveniently designate code that executes on the master thread and is skipped by the other threads.
There is no implied barrier on entry to or exit from a master section of code. Nested master sections are
ignored. Further, branching into or out of a master section is not supported.
Examples:
Example of MASTER...END MASTER directive
PROGRAM MASTER_USE
INTEGER A(0:1)
INTEGER omp_get_thread_num
A=-1
!$OMP PARALLEL
A(omp_get_thread_num()) = omp_get_thread_num()
!$OMP MASTER
PRINT *, "YOU SHOULD ONLY
SEE THIS ONCE"
!$OMP END MASTER
!$OMP END PARALLEL
PRINT *, "A(0)=",
A(0), " A(1)=", A(1)
END
Example of omp master pragma
#include
#include
main(){
int a[2]={-1,-1};Chapter 16. OpenMP Reference Information
251
#pragma omp parallel
{
a[omp_get_thread_num()] = omp_get_thread_num();
#pragma omp master
printf("YOU SHOULD ONLY SEE THIS ONCE\n");
}
printf("a[0]=%d, a[1]=%d\n",a[0],a[1]);
}
ORDERED
The OpenMP ORDERED directive and omp ordered pragma allow the user to identify a portion of code within
a ordered code block that must be executed in the original, sequential order, while allowing parallel execution
of statements outside the code block.
Syntax:
!$OMP ORDERED
< Fortran code block executed by
processor >
!$OMP END ORDERED
#pragma omp ordered
< C/C++ structured block >
Usage:
The ORDERED directive can appear only in the dynamic extent of a DO or PARALLEL DO directive that includes
the ORDERED clause. The ordered pragma can appear only in the dynamic extent of a for or parallel for
pragma that includes the ordered clause. The structured code block between the ORDERED / END ORDERED
directives or after the ordered pragma is executed by only one thread at a time, and in the order of the loop
iterations. This sequentializes the ordered code block while allowing parallel execution of statements outside
the code block. The following additional restrictions apply to the ORDERED directive and ordered pragma:
• The ordered code block must be a structured block. It is illegal to branch into or out of the block.
• It is illegal to branch into or out of the block.
• A given iteration of a loop with a DO directive or omp for pragma cannot execute the same ORDERED
directive or omp ordered pragma more than once, and cannot execute more than one ORDERED directive
or omp ordered pragma.
PARALLEL ... END PARALLEL and omp parallel
The OpenMP PARALLEL ...END PARALLEL directive and OpenMP omp parallel pragma support a fork/join
execution model in which a single thread executes all statements until a parallel region is encountered.
Syntax:
!$OMP PARALLEL [Clauses]
< Fortran code executed in body of
parallel region >
!$OMP END PARALLEL
#pragma omp parallel [clauses]
< C/C++ structured block >
Clauses:PGI® User’s Guide
252
For Directives:
PRIVATE(list)
SHARED(list)
DEFAULT(PRIVATE | SHARED | NONE)
FIRSTPRIVATE(list)
REDUCTION([{operator | intrinsic}:] list)
COPYIN(list)
IF(scalar_logical_expression)
NUM_THREADS(scalar_integer_expression)
For Pragmas:
private(list)
shared(list)
default(shared | none)
firstprivate(list)
reduction(operator: list)
copyin (list)
if (scalar_expression)
num_threads(scalar_integer_expression)
Usage:
This directive pair or pragma declares a region of parallel execution. It directs the compiler to create an
executable in which the statements within the structured block, such as between PARALLEL and PARALLEL END
for directives, are executed by multiple lightweight threads. The code that lies within this structured block is
called a parallel region.
The OpenMP parallelization directives or pragmas support a fork/join execution model in which a single
thread executes all statements until a parallel region is encountered. At the entrance to the parallel region, a
system-dependent number of symmetric parallel threads begin executing all statements in the parallel region
redundantly. These threads share work by means of work-sharing constructs such as parallel DO loops or For
loops.
• The number of threads in the team is controlled by the OMP_NUM_THREADS environment variable. If
OMP_NUM_THREADS is not defined, the program executes parallel regions using only one processor.
• Branching into or out of a parallel region is not supported.
• All other shared-memory parallelization directives or pragmas must occur within the scope of a parallel
region. Nested PARALLEL ... END PARALLEL directive pairs or omp parallel pragmas are not supported and
are ignored.
• There is an implicit barrier at the end of the parallel region, which, in the directive, is denoted by the END
PARALLEL directive. When all threads have completed execution of the parallel region, a single thread
resumes execution of the statements that follow.
NOTE
By default, there is no work distribution in a parallel region. Each active thread executes the entire
region redundantly until it encounters a directive or pragma that specifies work distribution. For work
distribution, see the DO, PARALLEL DO, or DOACROSS directives or the omp for pragma.
Examples:
PARALELL ... END PARALLEL directive example:
PROGRAM WHICH_PROCESSOR_AM_I
INTEGER A(0:1)
INTEGER omp_get_thread_num
A(0) = -1
A(1) = -1
!$OMP PARALLEL
A(omp_get_thread_num()) =
omp parallel pragma Example
#include
#include
main(){
int a[2]={-1,-1};
#pragma omp parallel
{
a[omp_get_thread_num()] =Chapter 16. OpenMP Reference Information
253
omp_get_thread_num()
!$OMP END PARALLEL
PRINT *, "A(0)=",A(0),
" A(1)=",A(1)
END
omp_get_thread_num();
}
printf("a[0] = %d,
a[1] = %d",a[0],a[1]);
}
Clause Usage:
PRIVATE: The variables specified in a PRIVATE list are private to each thread in a team. In effect, the compiler
creates a separate copy of each of these variables for each thread in the team. When an assignment to a private
variable occurs, each thread assigns to its local copy of the variable. When operations involving a private
variable occur, each thread performs the operations using its local copy of the variable.
Tips about private variables:
• Variables declared private in a parallel region are undefined upon entry to the parallel region. If the first
use of a private variable within the parallel region is in a right-hand-side expression, the results of the
expression will be undefined (i.e., this is probably a coding error).
• Variables declared private in a parallel region are undefined when serial execution resumes at the end of
the parallel region.
SHARED: Variables specified in a SHARED list are shared between all threads in a team, meaning that all
threads access the same storage area for SHARED data.
DEFAULT: The DEFAULT clause lets you specify the default attribute for variables in the lexical extent of the
parallel region. Individual clauses specifying PRIVATE, SHARED, and so on, override the declared DEFAULT.
Specifying DEFAULT(NONE) declares that there is no implicit default; thus, each variable in the parallel region
must be explicitly listed with an attribute of PRIVATE, SHARED, FIRSTPRIVATE, LASTPRIVATE, or REDUCTION.
FIRSTPRIVATE: Variables that appear in the list of a FIRSTPRIVATE clause are subject to the same semantics as
PRIVATE variables; however, these variables are initialized from the original object existing prior to entering
the parallel region.
REDUCTION: Variables that appear in the list of a REDUCTION clause must be SHARED. A private copy of each
variable in list is created for each thread as if the PRIVATE clause had been specified. Each private copy is
initialized according to the operator as specified in the following table:
Table 16.1. Initialization of REDUCTION Variables
For Directives For Pragmas
Operator /
Intrinsic
Initialization Operator Initialization
+ 0 + 0
* 1 * 1
- 0 - 0
.AND. .TRUE. & ~0
.OR. .FALSE. | 0PGI® User’s Guide
254
For Directives For Pragmas
Operator /
Intrinsic
Initialization Operator Initialization
.EQV. .TRUE. ^ 0
.NEQV. .FALSE. && 1
MAX Smallest Representable Number || 0
MIN Largest Representable Number
IAND All bits on
IOR 0
IEOR 0
At the end of the parallel region, a reduction is performed on the instances of variables appearing in list using
operator or intrinsic as specified in the REDUCTION clause. The initial value of each REDUCTION variable is
included in the reduction operation. If the {operator | intrinsic}: portion of the REDUCTION clause is omitted,
the default reduction operator is “+” (addition).
The COPYIN clause applies only to THREADPRIVATE common blocks. In the presence of the COPYIN clause,
data from the master thread’s copy of the common block is copied to the threadprivate copies upon entry to
the parallel region.
In the presence of an IF clause, the parallel region is executed in parallel only if the corresponding
scalar_logical_expression evaluates to .TRUE.. Otherwise, the code within the region is executed by a single
processor, regardless of the value of the environment variable OMP_NUM_THREADS.
If the NUM_THREADS clause is present, the corresponding scalar_integer_expression must evaluate
to a positive integer value. This value sets the maximum number of threads used during execution of
the parallel region. A NUM_THREADS clause overrides either a previous call to the library routine
omp_set_num_threads() or the setting of the OMP_NUM_THREADS environment variable.
PARALLEL DO
The OpenMP PARALLEL DO directive is a shortcut for a PARALLEL region that contains a single DO directive.
Note
The OpenMP PARALLEL DO or DO directive must be immediately followed by a DO statement (DOstmt as defined by R818 of the ANSI Fortran standard). If you place another statement or an OpenMP
directive between the PARALLEL DO or DO directive and the DO statement, the compiler issues a
syntax error.
Syntax:
!$OMP PARALLEL DO [CLAUSES]
< Fortran DO loop to be executed
in parallel >
#pragma omp parallel [clauses]
< C/C++ structured block >Chapter 16. OpenMP Reference Information
255
[!$OMP END PARALLEL DO]
Clauses:
PRIVATE(list)
SHARED(list)
DEFAULT(PRIVATE | SHARED | NONE)
FIRSTPRIVATE(list)
LASTPRIVATE(list)
REDUCTION({operator | intrinsic} : list)
COPYIN (list)
IF(scalar_logical_expression)
NUM_THREADS(scalar_integer_expression)
SCHEDULE (type [, chunk])
ORDERED
Usage:
The semantics of the PARALLEL DO directive are identical to those of a parallel region containing only a single
parallel DO loop and directive. Note that the END PARALLEL DO directive is optional. The available clauses are
as defined in “PARALLEL ... END PARALLEL and omp parallel ,” on page 251 and “DO ... END DO and omp
for ”.
PARALLEL SECTIONS
The OpenMP PARALLEL SECTIONS / END SECTIONS directive pair and the omp parallel sections pragma define
tasks to be executed in parallel; that is, they define a non-iterative work-sharing construct without the need to
define an enclosing parallel region.
Syntax:
!$OMP PARALLEL SECTIONS [CLAUSES]
[!$OMP SECTION]
< Fortran code block executed by
processor i >
[!$OMP SECTION]
< Fortran code block executed by
processor j >
...
!$OMP END SECTIONS [NOWAIT]
#pragma omp parallel sections [clauses]
{
[#pragma omp section]
< C/C++ structured block executed
by processor i >
[#pragma omp section]
< C/C++ structured block executed
by processor j >
...
}
Clauses:
Directive clauses:
PRIVATE(list)
SHARED(list)
DEFAULT(PRIVATE | SHARED | NONE)
FIRSTPRIVATE(list)
LASTPRIVATE(list)
REDUCTION({operator | intrinsic} : list)
COPYIN (list)
IF(scalar_logical_expression)
NUM_THREADS(scalar_integer_expression)
Pragma clauses:
private(list)
shared(list)
default(shared | none)
firstprivate(list)
lastprivate (list)
reduction({operator: list)
copyin (list)
if (scalar_expression)
num_threads(scalar_integer_expression)PGI® User’s Guide
256
nowait
Usage:
The PARALLEL SECTIONS / END SECTIONS directive pair and the omp parallel sections pragma define a noniterative work-sharing construct without the need to define an enclosing parallel region. Each section is
executed by a single processor. If there are more processors than sections, some processors will have no work
and will jump to the implied barrier at the end of the construct. If there are more sections than processors,
one or more processors will execute more than one section.
A SECTION directive may only appear within the lexical extent of the enclosing PARALLEL SECTIONS / END
SECTIONS directives. In addition, the code within the PARALLEL SECTIONS / END SECTIONS directives must be
a structured block, and the code in each SECTION must be a structured block.
Semantics are identical to a parallel region containing only an omp sections pragma and the associated
structured block. The available clauses are as defined in “PARALLEL ... END PARALLEL and omp parallel ,” on
page 251 and “DO ... END DO and omp for ”.
PARALLEL WORKSHARE
The OpenMP PARALLEL WORKSHARE directive u...
Syntax:
!$OMP PARALLEL WORKSHARE [CLAUSES]
< Fortran structured block to be
executed in parallel >
[!$OMP END PARALLEL WORKSHARE]
!$OMP PARALLEL DO [CLAUSES]
< Fortran DO loop to be executed
in parallel >
[!$OMP END PARALLEL DO]
#pragma omp parallel [clauses]
< C/C++ structured block >
Clauses:
Directive clauses:
PRIVATE(list)
SHARED(list)
DEFAULT(PRIVATE | SHARED | NONE)
FIRSTPRIVATE(list)
LASTPRIVATE(list)
REDUCTION({operator | intrinsic} : list)
COPYIN (list)
IF(scalar_logical_expression)
NUM_THREADS(scalar_integer_expression)
SCHEDULE (type [, chunk])
ORDERED
Pragma clauses:
private(list)
shared(list)
default(shared | none)
firstprivate(list)
lastprivate (list)
reduction({operator: list)
copyin (list)
if (scalar_expression)
num_threads(scalar_integer_expression)
nowait
Usage:
The semantics of the PARALLEL WORKSHARE directive are identical to those of a parallel region containing a
single WORKSHARE construct.Chapter 16. OpenMP Reference Information
257
The END PARALLEL WORKSHARE directive is optional, and that NOWAIT may not be specified on an END
PARALLEL WORKSHARE directive. The available clauses are as defined in “PARALLEL ... END PARALLEL and
omp parallel ,” on page 251.
SECTIONS … END SECTIONS
The OpenMP SECTIONS / END SECTIONS directive pair and the omp sections pragma define a non-iterative
work-sharing construct within a parallel region which each section is executed by a single processor.
Syntax:
!$OMP SECTIONS [ Clauses ]
[!$OMP SECTION]
< Fortran code block executed by
processor i >
[!$OMP SECTION]
< Fortran code block executed by
processor j >
...
!$OMP END SECTIONS [NOWAIT]
#pragma omp sections [ Clauses ]
{
[#pragma omp section]
< C/C++ structured block executed
by processor i >
[#pragma omp section]
< C/C++ structured block executed
by processor j >
...
}
Clauses:
For Directives:
PRIVATE (list)
FIRSTPRIVATE (list)
LASTPRIVATE (list)
REDUCTION({operator|intrinsic} : list)
For Pragmas:
private (list)
firstprivate (list)
lastprivate (list)
reduction(operator: list)
nowait
Usage:
The SECTIONS / END SECTIONS directive pair and the omp sections pragma define a non-iterative worksharing construct within a parallel region. Each section is executed by a single processor. If there are more
processors than sections, some processors have no work and thus jump to the implied barrier at the end of
the construct. If there are more sections than processors, one or more processors must execute more than
one section.
A SECTION directive or omp sections pragma may only appear within the lexical extent of the enclosing
SECTIONS / END SECTIONS directives or omp sections pragma. In addition, the code within the SECTIONS /
END SECTIONS directives or omp sections pragma must be a structured block, and the code in each section
must be a structured block.
The available clauses are as defined in “PARALLEL ... END PARALLEL and omp parallel ,” on page 251 and
“DO ... END DO and omp for ”.
SINGLE ... END SINGLE
The SINGLE ...END SINGLE directive or omp parallel pragma designates code that executes on a single thread
and that is skipped by the other threads.PGI® User’s Guide
258
Syntax:
!$OMP SINGLE [Clauses]
< Fortran code executed in body of
SINGLE processor section >
!$OMP END SINGLE [NOWAIT]
#pragma omp parallel [clauses]
< C/C++ structured block >
Clauses:
PRIVATE(list)
FIRSTPRIVATE(list)
COPYPRIVATE(list)
Usage:
In a parallel region of code, there may be a sub-region of code that will only execute correctly on a single
thread. Instead of ending the parallel region before this subregion and then starting it up again after this
subregion, the SINGLE ... END SINGLE directive pair lets you conveniently designate code that executes on a
single thread and is skipped by the other threads. There is an implied barrier on exit from a SINGLE ... END
SINGLE section of code unless the optional NOWAIT clause is specified.
Nested single process sections are ignored. Branching into or out of a single process section is not supported.
Examples:
PROGRAM SINGLE_USE
INTEGER A(0:1)
INTEGER omp_get_thread_num()
!$OMP PARALLEL
A(omp_get_thread_num()) = omp_get_thread_num()
!$OMP SINGLE
PRINT *, "YOU SHOULD ONLY
SEE THIS ONCE"
!$OMP END SINGLE
!$OMP END PARALLEL
PRINT *, "A(0)=",
A(0), " A(1)=", A(1)
END
The section“PARALLEL ... END PARALLEL and omp parallel ,” on page 251 describes PRIVATE and
FIRSTPRIVATE clause.
The COPYPRIVATE clause causes the variables in list to be copied from the private copies in the single thread
that executes the SINGLE region to the other copies in all other threads of the team at the end of the SINGLE
region. The COPYPRIVATE clause must not be used with NOWAIT.
THREADPRIVATE
The OpenMP THREADPRIVATE directive identifies a Fortran common block as being private to each thread.
The omp threadprivate pragma identifies a global variable as being private to each thread.
Syntax:
!$OMP THREADPRIVATE (list) #pragma omp threadprivate (list)
Usage:Chapter 16. OpenMP Reference Information
259
Where list is a comma-separated list of named variables to be made private to each thread or named common
blocks to be made private to each thread but global within the thread. Common block names must appear
between slashes, such as /common_block_name/. This directive must appear in the declarations section
of a program unit after the declaration of any common blocks or variables listed. On entry to a parallel
region, data in a THREADPRIVATE common block or variable is undefined unless COPYIN is specified on the
PARALLEL directive. When a common block or variable that is initialized using DATA statements appears in a
THREADPRIVATE directive, each thread’s copy is initialized once prior to its first use.
Where list is a list of variables to be made private to each thread but global within the thread. This pragma
must appear in the declarations section of a program unit after the declaration of any variables listed. On entry
to a parallel region, data in a threadprivate variable is undefined unless copyin is specified on the omp parallel
pragma. When a variable appears in an omp threadprivate pragma, each thread’s copy is initialized once at
an unspecified point prior to its first use as the master copy would be initialized in a serial execution of the
program.
Restrictions:
The following restrictions apply to the THREADPRIVATE directive or omp threadprivate pragma:
• The THREADPRIVATE directive must appear after every declaration of a thread private common block.
• The omp threadprivate pragma must appear after the declaration of every threadprivate variable included in
list.
• Only named common blocks can be made thread private
• It is illegal for a THREADPRIVATE common block or its constituent variables to appear in any clause other
than a COPYIN clause.
• A variable can appear in a THREADRIVATE directive only in the scope in which it is declared. It must not be
an element of a common block or be declared in an EQUIVALENCE statement.
• A variable that appears in a THREADPRIVATE directive and is not declared in the scope of a module must
have the SAVE attribute.
• If a variable is specified in an omp threadprivate pragma in one translation unit, it must be specified in an
omp threadprivate pragma in every translation unit in which it appears.
• The address of an omp threadprivate variable is not an address constant.
• The address of an omp threadprivate variable is not an address constant.
• An omp threadprivate variable must not have an incomplete type or a reference type.
WORKSHARE ... END WORKSHARE
The OpenMP WORKSHARE … END WORKSHARE directive pair or omp parallel pragma provides a mechanism
to effect parallel execution of non-iterative but implicitly data parallel constructs.
Syntax:
!$OMP WORKSHARE
< Fortran structured block to be
#pragma omp parallel [clauses]
< C/C++ structured block >PGI® User’s Guide
260
executed in parallel >
!$OMP END WORKSHARE [NOWAIT]
Usage:
The Fortran structured block enclosed by the WORKSHARE … END WORKSHARE directive pair can consist
only of the following types of statements and constructs:
• Array assignments
• Scalar assignments
• FORALL statements or constructs
• WHERE statements or constructs
• OpenMP ATOMIC , CRITICAL or PARALLEL constructs
The work implied by the above statements and constructs is split up between the threads executing the
WORKSHARE construct in a way that is guaranteed to maintain standard Fortran semantics. The goal of
the WORKSHARE construct is to effect parallel execution of non-iterative but implicitly data parallel array
assignments, FORALL, and WHERE statements and constructs intrinsic to the Fortran language beginning with
Fortran 90. The Fortran structured block contained within a WORKSHARE construct must not contain any userdefined function calls unless the function is ELEMENTAL.
Directive and Pragma Clauses
Some directives and pragmas accept clauses that further allow a user to control the scope attributes of
variables for the duration of the directive or pragma. Not all clauses are allowed on all directives, so the
clauses that are valid are included with the description of the directive and pragma. Typically, if no data scope
clause is specified for variables, the default scope is share.
The following table provides a brief summary of the clauses associated with OPENMP directives and pragmas
that PGI supports. For complete information on these clauses, refer to the OpenMP documentation available on
the WorldWide Web.
Table 16.2. Directive and Pragma Clauses
Clause Description
copyin Allows threads to access the master thread's value, for a threadprivate
variable. You assign the same value to threadprivate variables for each
thread in the team executing the parallel region. Then, for each variable
specified, the value of the variable in the master thread of the team
is copied to the threadprivate copies at the beginning of the parallel
region.
copyprivate(list) Specifies that one or more variables should be shared among all
threads. This clause provides a mechanism to use a private variable to
broadcast a value from one member of a team to the other members.
default (OpenMP) Specifies the behavior of unscoped variables in a parallel region, such
as the data-sharing attributes of variables.Chapter 16. OpenMP Reference Information
261
Clause Description
firstprivate(list) Specifies that each thread should have its own instance of a variable,
and that each variable in the list should be initialized with the value of
the original variable, because it exists before the parallel construct.
if (OpenMP) Specifies whether a loop should be executed in parallel or in serial.
lastprivate(list) Specifies that the enclosing context's version of the variable is set equal
to the private version of whichever thread executes the final iteration
(for-loop construct) or last section (#pragma sections).
nowait Overrides the barrier implicit in a directive.
num_threads Sets the number of threads in a thread team.
ordered (OpenMP Clauses) Required on a parallel for (OpenMP) statement if an ordered (OpenMP
Directives) directive is to be used in the loop.
private (OpenMP) Specifies that each thread should have its own instance of a variable.
reduction({operator |
intrinsic } : list)
Specifies that one or more variables that are private to each thread are
the subject of a reduction operation at the end of the parallel region.
schedule(type [,chunk]) Applies to the for (OpenMP) directive, allowing the user to specify the
chunking method for parallelization. Work is assigned to threads in
different manners depending on the scheduling type or chunk size used.
shared (OpenMP) Specifies that one or more variables should be shared among all
threads. All threads within a team access the same storage area for
shared variables
Schedule Clause
The SCHEDULE clause specifies how iterations of the DO or for loop are divided up between processors. Given
a SCHEDULE (type [, chunk]) clause, the type can be STATIC, DYNAMIC, GUIDED, or RUNTIME, defined in the
following list.
Note
For pragmas, the values for the clause are lower case static, dynamic, guided, or runtime. For
simplicity, we use the directive uppercase value in the following information.
• When SCHEDULE (STATIC, chunk) is specified, iterations are allocated in contiguous blocks of size chunk.
The blocks of iterations are statically assigned to threads in a round-robin fashion in order of the thread ID
numbers. The chunk must be a scalar integer expression. If chunk is not specified, a default chunk size is
chosen equal to:
(number_of_iterations + omp_num_threads()
- 1) / omp_num_threads()
• When SCHEDULE (DYNAMIC, chunk) is specified, iterations are allocated in contiguous blocks of size
chunk. As each thread finishes a piece of the iteration space, it dynamically obtains the next set of iterations.
The chunk must be a scalar integer expression. If no chunk is specified, a default chunk size is chosen
equal to 1.PGI® User’s Guide
262
• When SCHEDULE (GUIDED, chunk) is specified, the chunk size is reduced in an exponentially decreasing
manner with each dispatched piece of the iteration space. Chunk specifies the minimum number of
iterations to dispatch each time, except when there are less than chunk iterations remaining to be
processed, at which point all remaining iterations are assigned. If no chunk is specified, a default chunk
size is chosen equal to 1.
• When SCHEDULE (RUNTIME) is specified, the decision regarding iteration scheduling is deferred until
runtime. The schedule type and chunk size can be chosen at runtime by setting the OMP_SCHEDULE
environment variable. If this environment variable is not set, the resulting schedule is equivalent to
SCHEDULE(STATIC).263
Chapter 17. Directives and Pragmas
Reference
As we mentioned in Chapter 6, “Using Directives and Pragmas,” on page 63, PGI Fortran compilers support
proprietary directives and pragmas.
This chapter contains detailed descriptions of PGI’s proprietary directives and pragmas.
PGI Proprietary Fortran Directive and C/C++ Pragma Summary
Directives are Fortran comments and pragmas are C/C++ comments that the user may supply in a source file
to provide information to the compiler. These comments alter the effects of certain command line options or
default behavior of the compiler. They provide pragmatic information that control the actions of the compiler
in a particular portion of a program without affecting the program as a whole. That is, while a command line
option affects the entire source file that is being compiled, directives and pragmas apply, or disable, the effects
of a command line option to selected subprograms or to selected loops in the source file, for example, to
optimize a specific area of code. Use directives and pragmas to tune selected routines or loops.
The Fortran directives may have any of the following forms:
!pgi$g directive
!pgi$r directive
!pgi$l directive
!pgi$ directive
Directives and pragmas override corresponding command-line options. For usage information such as the
scope and related command-line options, refer to Chapter 6, “Using Directives and Pragmas,” on page 63.
altcode (noaltcode)
This directive or pragma instructs the compiler to generate alternate code for vectorized or parallelized loops.
The noaltcode directive or pragma disables generation of alternate code.
Scope: This directive or pragma affects the compiler only when –Mvect=sse or –Mconcur is enabled on the
command line.PGI® User’s Guide
264
cpgi$ altcode
Enables alternate code (altcode) generation for vectorized loops. For each loop the compiler decides
whether to generate altcode and what type(s) to generate, which may be any or all of: altcode without
iteration peeling, altcode with non-temporal stores and other data cache optimizations, and altcode based
on array alignments calculated dynamically at runtime. The compiler also determines suitable loop count
and array alignment conditions for executing the alternate code.
cpgi$ altcode alignment
For a vectorized loop, if possible generate an alternate vectorized loop containing additional aligned
moves which is executed if a runtime array alignment test is passed.
cpgi$ altcode [(n)] concur
For each auto-parallelized loop, generate an alternate serial loop to be executed if the loop count is less
than or equal to n. If n is omitted or n is 0, the compiler determines a suitable value of n for each loop.
cpgi$ altcode [(n)] concurreduction
This directive sets the loop count threshold for parallelization of reduction loops to n. For each autoparallelized reduction loop, generate an alternate serial loop to be executed if the loop count is less than
or equal to n. If n is omitted or n is 0, the compiler determines a suitable value of n for each loop.
cpgi$ altcode [(n)] nontemporal
For a vectorized loop, if possible generate an alternate vectorized loop containing non-temporal stores and
other cache optimizations to be executed if the loop count is greater than n. If n is omitted or n is 1, the
compiler determines a suitable value of n for each loop. The alternate code is optimized for the case when
the data referenced in the loop does not all fit in level 2 cache.
cpgi$ altcode [(n)] nopeel
For a vectorized loop where iteration peeling is performed by default, if possible generate an alternate
vectorized loop without iteration peeling to be executed if the loop count is less than or equal to n. If n is
omitted or n is 1, the compiler determines a suitable value of n for each loop, and in some cases it may
decide not to generate an alternate unpeeled loop.
cpgi$ altcode [(n)] vector
For each vectorized loop, generate an alternate scalar loop to be executed if the loop count is less than or
equal to n. If n is omitted or n is 1, the compiler determines a suitable value of n for each loop.
cpgi$ noaltcode
This directive sets the loop count thresholds for parallelization of all innermost loops to 0, and disables
alternate code generation for vectorized loops.
assoc (noassoc)
This directive or pragma toggles the effects of the –Mvect=noassoc command-line option, an optimization
–M control.
By default, when scalar reductions are present the vectorizer may change the order of operations so that it can
generate better code (e.g., dot product). Such transformations may change the result of the computation due
to roundoff error. The noassoc directive disables these transformations.
Scope: This directive or pragma affects the compiler only when –Mvect=sse is enabled on the command
line.Chapter 17. Directives and Pragmas Reference
265
bounds (nobounds)
This directive or pragma alters the effects of the –Mbounds command line option. This directive enables
the checking of array bounds when subscripted array references are performed. By default, array bounds
checking is not performed.
cncall (nocncall)
Loops within the specified scope are considered for parallelization, even if they contain calls to user-defined
subroutines or functions. A nocncall directive cancels the effect of a previous cncall.
concur (noconcur)
This directive or pragma alters the effects of the –Mconcur command-line option. The directive instructs the
auto-parallelizer to enable auto-concurrentization of loops. If concur is specified, multiple processors will
be used to execute loops which the auto-parallelizer determines to be parallelizable. The noconcur directive
disables these transformations, but use of concur overrides previous noconcur statements.
Scope: This directive or pragma affects the compiler only when –Mconcur is enabled on the command line.
depchk (nodepchk)
This directive or pragma alters the effects of the –Mdepchk command line option. When potential data
dependencies exist, the compiler, by default, assumes that there is a data dependence that in turn may inhibit
certain optimizations or vectorizations. nodepchk directs the compiler to ignore unknown data dependencies.
eqvchk (noeqvchk)
When examining data dependencies, noeqvchk directs the compiler to ignore any dependencies between
variables appearing in EQUIVALENCE statements.
fcon (nofcon)
This C/C++ pragma alters the effects of the –Mfcon (a –M Language control) command-line option.
The pragma instructs the compiler to treat non-suffixed floating-point constants as float rather than double. By
default, all non-suffixed floating-point constants are treated as double.
Note
Only routine or global scopes are allowed for this C/C++ pragma.
invarif (noinvarif)
This directive or pragma has no corresponding command-line option. Normally, the compiler removes certain
invariant if constructs from within a loop and places them outside of the loop. The directive noinvarif directs
the compiler to not move such constructs. The directive invarif toggles a previous noinvarif.PGI® User’s Guide
266
ivdep
The ivdep directive is equivalent to the directive nodepchk.
lstval (nolstval)
This directive or pragma has no corresponding command-line option. The compiler determines whether the
last values for loop iteration control variables and promoted scalars need to be computed. In certain cases,
the compiler must assume that the last values of these variables are needed and therefore computes their last
values. The directive nolstval directs the compiler not to compute the last values for those cases.
opt
The syntax of this directive or pragma is:
cpgi$ opt=
where, the optional is r or g and is an integer constant representing the optimization level
to be used when compiling a subprogram (routine scope) or all subprograms in a file (global scope). The opt
directive overrides the value specified by the command line option –On.
safe (nosafe)
This C/C++ pragma has no corresponding command-line option. By default, the compiler assumes that all
pointer arguments are unsafe. That is, the storage located by the pointer can be accessed by other pointers.
The forms of the safe pragma are:
#pragma [scope] [no]safe
#pragma safe (variable [, variable]...)
where scope is either global or routine.
When the pragma safe is not followed by a variable name (or name list), all pointer arguments appearing in a
routine (if scope is routine) or all routines (if scope is global) will be treated as safe.
If variable names occur after safe, each name is the name of a pointer argument in the current function. The
named argument is considered to be safe.
Note
If just one variable name is specified, the surrounding parentheses may be omitted.
safe_lastval
During parallelization scalars within loops need to be privatized. Problems are possible if a scalar is accessed
outside the loop. in this exampl a problem results since the value of t may not be computed on the last
iteration of the loop.:
do i = 1, N
if( f(x(i)) > 5.0 then)
t = x(i)
endif
enddoChapter 17. Directives and Pragmas Reference
267
v = t
If a scalar assigned within a loop is used outside the loop, we normally save the last value of the scalar.
Essentially the value of the scalar on the "last iteration" is saved, in this case when i = N.
If the loop is parallelized and the scalar is not assigned on every iteration, it may be difficult to determine on
what iteration t is last assigned, without resorting to costly critical sections. Analysis allows the compiler to
determine if a scalar is assigned on every iteration, thus the loop is safe to parallelize if the scalar is used later.
An example loop is:
do i = 1, N
if( x(i) > 0.0 ) then
t = 2.0
else
t = 3.0
endif
y(i) = ...t...
enddo
v = t
where t is assigned on every iteration of the loop. However, there are cases where a scalar may be
privatizable. If it is used after the loop, it is unsafe to parallelize. Examine this loop:
do i = 1,N
if( x(i) > 0.0 ) then
t = x(i)
...
...
y(i) = ...t..
endif
enddo
v = t
where each use of t within the loop is reached by a definition from the same iteration. Here t is privatizable,
but the use of t outside the loop may yield incorrect results since the compiler may not be able to detect on
which iteration of the parallelized loop t is assigned last.
The compiler detects the above cases. Where a scalar is used after the loop, but is not defined on every
iteration of the loop, parallelization will not occur.
If you know that the scalar is assigned on the last iteration of the loop, making it safe to parallelize the loop,
a directive or pragma is available to let the compiler know the loop is safe to parallelize. Use the following
C pragma to tell the compiler that for a given loop the last value computed for all scalars make it safe to
parallelize the loop:
cpgi$l safe_lastva
#pragma loop safe_lastval
In addition, a command-line option,-Msafe_lastval, provides this information for all loops within the
routines being compiled, essentially providing global scope.
safeptr (nosafeptr)
The directive or pragma safeptr directs the compiler to treat pointer variables of the indicated storage class
as safe. The pragma nosafeptr directs the compiler to treat pointer variables of the indicated storage class as
unsafe. This pragma alters the effects of the –Msafeptr command-line option.PGI® User’s Guide
268
The syntax of this pragma is:
cpgi$[] value
#pragma [scope] value
where value is:
[no]safeptr={arg|local|auto|global|static|all},...
Note that the values local and auto are equivalent.
For example, in a file containing multiple functions, the command-line option –Msafeptr might be helpful for
one function, but can’t be used because another function in the file would produce incorrect results. In such a
file, the safeptr pragma, used with routine scope could improve performance and produce correct results.
single (nosingle)
The pragma single directs the compiler not to implicityly convert float values to double non-prototyped
functions. This can result in faster code if the program uses only float parameters.
Note
Since ANSI C specifies that floats must be converted to double, this pragma results in non-ANSI
conforming code. Valid only for routine or global scope.
tp
Note
The tp directive or pragma can only be applied at the routine or global level. For more information
about these levels, refer to“Scope of C/C++ Pragmas and Command-Line Options,” on page 67.
You use the directive or pragma tp to specify one or more processor targets for which to generate code.
cpgi$ tp [target]...
See Table 2, “Processor Options,” on page xxvi for a list of targets that can be used as parameters to the tp
directive. For more information on unified binaries, refer to “Processor-Specific Optimization and the Unified
Binary,” on page 36.
unroll (nounroll)
Note
The unroll directive or pragma has no effect on vectorized loops.
The directive or pragma nounroll disables loop unrolling while unroll enables unrolling. The directive or
pragma takes arguments c and n. A c specifies that c (complete unrolling should be turned on or off) An n
specifies that n (count) unrolling should be turned on or off. In addition, the following arguments may be
added to the unroll directive:
cpgi$ unroll = c:vChapter 17. Directives and Pragmas Reference
269
This sets the threshold to which c unrolling applies; v is a constant; a loop whose constant loop count is <= v
is completely unrolled.
cpgi$ unroll = n:v
This adjusts threshold to which n unrolling applies; v is a constant; a loop to which n unrolling applies is
unrolled v times.
The directives unroll and nounroll only apply if –Munroll is selected on the command line.
vector (novector)
The directive or pragma novector is used to disable vectorization. The directive vector is used to re-enable
vectorization after a previous novector directive. The directives vector and novector only apply if –Mvect has
been selected on the command line.
vintr (novintr)
The directive or pragma novintr directs the vectorizer to disable recognition of vector intrinsics. The directive
vintr is used to re-enable recognition of vector intrinsics after a previous novintr directive. The directives vintr
and novintr only apply if –Mvect has been selected on the command line.270271
Chapter 18. Run-time Environment
This chapter describes the programming model supported for compiler code generation, including register
conventions and calling conventions for x86 and x64 processor-based systems. It addresses these conventions
for processors running linux86 or Win32 operating systems, for processors running linux86-64 operating
systems, and for processors running Win64 operating systems.
Note
In this chapter we sometimes refer to word, halfword, and double word. The equivalent byte
information is word (4 byte), halfword (2 byte), and double word (8 byte).
Linux86 and Win32 Programming Model
This section defines compiler and assembly language conventions for the use of certain aspects of an x86
processor running a linux86 or Win32 operating system. These standards must be followed to guarantee that
compilers, application programs, and operating systems written by different people and organizations will
work together. The conventions supported by the PGCC ANSI C compiler implement the application binary
interface (ABI) as defined in the System V Application Binary Interface: Intel Processor Supplement and the
System V Application Binary Interface, listed in the “Related Publications” section in the Preface.
Function Calling Sequence
This section describes the standard function calling sequence, including the stack frame, register usage, and
parameter passing.
Register Usage Conventions
The following table defines the standard for register allocation. The 32-bit x86 Architecture provides a number
of registers. All the integer registers and all the floating-point registers are global to all procedures in a
running program.
Table 18.1. Register Allocation
Type Name Purpose
General %eax integer return valuePGI® User’s Guide
272
Type Name Purpose
%edx dividend register (for divide operations)
%ecx count register (shift and string operations)
%ebx local register variable
%ebp optional stack frame pointer
%esi local register variable
%edi local register variable
%esp stack pointer
Floating-point %st(0) floating-point stack top, return value
%st(1) floating-point next to stack top
%st(...)
%st(7) floating-point stack bottom
In addition to the registers, each function has a frame on the run-time stack. This stack grows downward from
high addresses. The next table shows the stack frame organization.
Table 18.2. Standard Stack Frame
Position Contents Frame
4n+8 (%ebp) argument word n previous
8 (%ebp) argument word 0
4 (%ebp) return address
0 (%ebp) caller's %ebp current
-4 (%ebp) n bytes of local
-n (%ebp) variables and temps
Several key points concerning the stack frame:
• The stack is kept double word aligned
• Argument words are pushed onto the stack in reverse order so the rightmost argument in C call syntax has
the highest address. A dummy word may be pushed ahead of the rightmost argument in order to preserve
doubleword alignment. All incoming arguments appear on the stack, residing in the stack frame of the
caller.
• An argument’s size is increased, if necessary, to make it a multiple of words. This may require tail padding,
depending on the size of the argument.
All registers on an x86 system are global and thus visible to both a calling and a called function. Registers
%ebp, %ebx, %edi, %esi, and %esp are non-volatile across function calls. Therefore, a function must preserve
these registers’ values for its caller. Remaining registers are volatile (scratch). If a calling function wants to
preserve such a register value across a function call, it must save its value explicitly.Chapter 18. Run-time Environment
273
Some registers have assigned roles in the standard calling sequence:
%esp
The stack pointer holds the limit of the current stack frame, which is the address of the stack’s bottommost, valid word. At all times, the stack pointer should point to a word-aligned area.
%ebp
The frame pointer holds a base address for the current stack frame. Consequently, a function has registers
pointing to both ends of its frame. Incoming arguments reside in the previous frame, referenced as
positive offsets from %ebp, while local variables reside in the current frame, referenced as negative offsets
from %ebp. A function must preserve this register value for its caller.
%eax
Integral and pointer return values appear in %eax. A function that returns a structure or union value
places the address of the result in %eax. Otherwise, this is a scratch register.
%esi, %edi
These local registers have no specified role in the standard calling sequence. Functions must preserve
their values for the caller.
%ecx, %edx
Scratch registers have no specified role in the standard calling sequence. Functions do not have to
preserve their values for the caller.
%st(0)
Floating-point return values appear on the top of the floating point register stack; there is no difference in
the representation of single or double-precision values in floating point registers. If the function does not
return a floating point value, then the stack must be empty.
%st(1) - %st(7)
Floating point scratch registers have no specified role in the standard calling sequence. These registers
must be empty before entry and upon exit from a function.
EFLAGS
The flags register contains the system flags, such as the direction flag and the carry flag. The direction flag
must be set to the “forward” (i.e., zero) direction before entry and upon exit from a function. Other user
flags have no specified role in the standard calling sequence and are not reserved.
Floating Point Control Word
The control word contains the floating-point flags, such as the rounding mode and exception masking.
This register is initialized at process initialization time and its value must be preserved.
Signals can interrupt processes. Functions called during signal handling have no unusual restriction on their
use of registers. Moreover, if a signal handling function returns, the process resumes its original execution
path with registers restored to their original values. Thus, programs and compilers may freely use all registers
without danger of signal handlers changing their values.
Function Return Values
Functions Returning Scalars or No Value
• A function that returns an integral or pointer value places its result in register %eax.PGI® User’s Guide
274
• A function that returns a long long integer value places its result in the registers %edx and %eax. The most
significant word is placed in %edx and the least significant word is placed in %eax.
• A floating-point return value appears on the top of the floating point stack. The caller must then remove
the value from the floating point stack, even if it does not use the value. Failure of either side to meet its
obligations leads to undefined program behavior. The standard calling sequence does not include any
method to detect such failures nor to detect return value type mismatches. Therefore, the user must declare
all functions properly. There is no difference in the representation of single-, double- or extended-precision
values in floating-point registers.
• Functions that return no value (also called procedures or void functions) put no particular value in any
register.
• A call instruction pushes the address of the next instruction (the return address) onto the stack. The return
instruction pops the address off the stack and effectively continues execution at the next instruction after the
call instruction. A function that returns a scalar or no value must preserve the caller's registers as described
above. Additionally, the called function must remove the return address from the stack, leaving the stack
pointer (%esp) with the value it had before the call instruction was executed.
Functions Returning Structures or Unions
If a function returns a structure or union, then the caller provides space for the return value and places its
address on the stack as argument word zero. In effect, this address becomes a hidden first argument.
A function that returns a structure or union also sets %eax to the value of the original address of the caller's
area before it returns. Thus, when the caller receives control again, the address of the returned object resides
in register %eax and can be used to access the object. Both the calling and the called functions must cooperate
to pass the return value successfully:
• The calling function must supply space for the return value and pass its address in the stack frame;
• The called function must use the address from the frame and copy the return value to the object so
supplied;
• The called function must remove this address from the stack before returning.
Failure of either side to meet its obligation leads to undefined program behavior. The standard function
calling sequence does not include any method to detect such failures nor to detect structure and union type
mismatches. Therefore, you must declare the function properly.
The following table illustrates the stack contents when the function receives control, after the call instruction,
and when the calling function again receives control, after the ret instruction.
Table 18.3. Stack Contents for Functions Returning struct/union
Position After Call After Return Position
4n+8 (%esp) argument word n argument word n 4n-4 (%esp)
8 (%esp) argument word 1 argument word 1 0 (%esp)Chapter 18. Run-time Environment
275
Position After Call After Return Position
4 (%esp) value address undefined
0 (%esp) return address
The following sections of this appendix describe where arguments appear on the stack. The examples are
written as if the function prologue described above had been used.
Argument Passing
Integral and Pointer Arguments
As mentioned, a function receives all its arguments through the stack; the last argument is pushed first. In the
standard calling sequence, the first argument is at offset 8(%ebp), the second argument is at offset 12(%ebp),
as previously shown in Table 18.3, “Stack Contents for Functions Returning struct/union”. Functions pass all
integer-valued arguments as words, expanding or padding signed or unsigned bytes and halfwords as needed.
Table 18.4. Integral and Pointer Arguments
Call Argument Stack Address
g(1, 2, 3, (void *)0); 1 8 (%ebp)
2 12 (%ebp)
3 16 (%ebp)
(void *) 0 20 (%ebp)
Floating-Point Arguments
The stack also holds floating-point arguments: single-precision values use one word and double-precision use
two. The example below uses only double-precision arguments.
Table 18.5. Floating-point Arguments
Call Argument Stack Address
h(1.414, 1, 2.998e10); word 0, 1.414 8 (%ebp)
word 1, 1.414 12 (%ebp)
1 16 (%ebp)
word 0 2.998e10 20 (%ebp)
word 1, 2.998e10 24 (%ebp)
Structure and Union Arguments
Structures and unions can have byte, halfword, or word alignment, depending on the constituents. An
argument’s size is increased, if necessary, to make it a multiple of words. This may require tail padding,PGI® User’s Guide
276
depending on the size of the argument. Structure and union arguments are pushed onto the stack in the
same manner as integral arguments, described above. This provides call-by-value semantics, letting the
called function modify its arguments without affecting the calling function’s object. In the example below, the
argument, s, is a structure consisting of more than 2 words.
Table 18.6. Structure and Union Arguments
Call Argument Stack Address
i(1,s); 1 8 (%ebp)
word 0, s 12 (%ebp)
word 1, s 16 (%ebp)
... ...
Implementing a Stack
In general, compilers and programmers must maintain a software stack. Register %esp is the stack pointer.
Register %esp is set by the operating system for the application when the program is started. The stack must be
a grow-down stack.
A separate frame pointer enables calls to routines that change the stack pointer to allocate space on the stack
at run-time (e.g. alloca). Some languages can also return values from a routine allocated on stack space
below the original top-of-stack pointer. Such a routine prevents the calling function from using %esp-relative
addressing to get at values on the stack. If the compiler does not call routines that leave %esp in an altered
state when they return, a frame pointer is not needed and is not used if the compiler option –Mnoframe is
specified.
Although not required, the stack should be kept aligned on 8-byte boundaries so that 8-byte locals are
favorably aligned with respect to performance. PGI's compilers allocate stack space for each routine in
multiples of 8 bytes.
Variable Length Parameter Lists.
Parameter passing in registers can handle a variable number of parameters. The C language uses a special
method to access variable-count parameters. The stdarg.h and varargs.h files define several functions to access
these parameters. A C routine with variable parameters must use the va_start macro to set up a data structure
before the parameters can be used. The va_arg macro must be used to access the successive parameters.
C Parameter Conversion.
In C, for a called prototyped function, the parameter type in the called function must match the argument
type in the calling function. If the called function is not prototyped, the calling convention uses the types of
the arguments but promotes char or short to int, and unsigned char or unsigned short to unsigned int and
promotes float to double, unless you use the ##Msingle option. For more information on the –Msingle option,
refer to Chapter 3. If the called function is prototyped, the unused bits of a register containing a char or short
parameter are undefined and the called function must extend the sign of the unused bits when needed.Chapter 18. Run-time Environment
277
Calling Assembly Language Programs
Example 18.1. C Program Calling an Assembly-language Routine
/* File: testmain.c */
main(){
long l_para1 = 0x3f800000;
float f_para2 = 1.0;
double d_para3 = 0.5;
float f_return;
extern float sum_3 (long para1, float para2, double para3);
f_return = sum_3(l_para1,f_para2, d_para3);
printf("Parameter one, type long = %08x\n",l_para1);
printf("Parameter two, type float = %f\n",f_para2);
printf("Parameter three, type double = %g\n",d_para3);
printf("The sum after conversion = %f\n",f_return);
}
# File: sum_3.s
# Computes ( para1 + para2 ) + para3
.text
.align 4
.long .EN1-sum_3+0xc8000000
.align 16
.globl sum_3
sum_3:
pushl %ebp
movl %esp,%ebp
subl $8,%esp
..EN1:
fildl 8(%ebp)
fadds 12(%ebp)
faddl 16(%ebp)
fstps -4(%ebp)
flds -4(%ebp)
addl $8,%esp
leave
ret
.type sum_3,@function
.size sum_3,.-sum_3
Linux86-64 Programming Model
This section defines compiler and assembly language conventions for the use of certain aspects of an x64
processor running a linux86-64 operating system. These standards must be followed to guarantee that
compilers, application programs, and operating systems written by different people and organizations will
work together. The conventions supported by the PGCC ANSI C compiler implement the application binary
interface (ABI) as defined in the System V Application Binary Interface: AMD64 Architecture Processor
Supplement and the System V Application Binary Interface, listed in the “Related Publications” section in the
Preface.
Note
The programming model used for Win64 and SUA64 differs from the Linux86-64 model. For more
information, refer to “Win64 Programming Model,” on page 287.PGI® User’s Guide
278
Function Calling Sequence
This section describes the standard function calling sequence, including the stack frame, register usage, and
parameter passing.
Register Usage Conventions.
The following table defines the standard for register allocation. The x64 Architecture provides a variety of
registers. All the general purpose registers, XMM registers, and x87 registers are global to all procedures in a
running program.
Table 18.7. Register Allocation
Type Name Purpose
General %rax 1st return register
%rbx callee-saved; optional base pointer
%rcx pass 4th argument to functions
%rdx pass 3rd argument to functions; 2nd return register
%rsp stack pointer
%rbp callee-saved; optional stack frame pointer
%rsi pass 2nd argument to functions
%rdi pass 1st argument to functions
%r8 pass 5th argument to functions
%r9 pass 6th argument to functions
%r10 temporary register; pass a function’s static chain pointer
%r11 temporary register
%r12-r15 callee-saved registers
XMM %xmm0-%xmm1 pass and return floating point arguments
%xmm2-%xmm7 pass floating point arguments
%xmm8-%xmm15 temporary registers
x87 %st(0) temporary register; return long double arguments
%st(1) temporary register; return long double arguments
%st(2) - %st(7) temporary registers
In addition to the registers, each function has a frame on the run-time stack. This stack grows downward from
high addresses. The next table shows the stack frame organization.
Table 18.8. Standard Stack Frame
Position Contents Frame
8n+16 (%rbp) argument eightbyte n previousChapter 18. Run-time Environment
279
Position Contents Frame
. . .
16 (%rbp) argument eightbyte 0
8 (%rbp) return address current
0 (%rbp) caller's %rbp current
-8 (%rbp) unspecified
. . .
0 (%rsp) variable size
-128 (%rsp) red zone
Key points concerning the stack frame:
• The end of the input argument area is aligned on a 16-byte boundary.
• The 128-byte area beyond the location of %rsp is called the red zone and can be used for temporary local
data storage. This area is not modified by signal or interrupt handlers.
• A call instruction pushes the address of the next instruction (the return address) onto the stack. The return
instruction pops the address off the stack and effectively continues execution at the next instruction after the
call instruction. A function must preserve non-volatile registers (described below). Additionally, the called
function must remove the return address from the stack, leaving the stack pointer (%rsp) with the value it
had before the call instruction was executed.
All registers on an x64 system are global and thus visible to both a calling and a called function. Registers
%rbx, %rsp, %rbp, %r12, %r13, %r14, and %r15 are non-volatile across function calls. Therefore, a function
must preserve these registers’ values for its caller. Remaining registers are volatile (scratch). If a calling
function wants to preserve such a register value across a function call, it must save its value explicitly.
Registers are used extensively in the standard calling sequence. The first six integer and pointer arguments
are passed in these registers (listed in order): %rdi, %rsi, %rdx, %rcx, %r8, %r9. The first eight floating point
arguments are passed in the first eight XMM registers: %xmm0, %xmm1, …, %xmm7. The registers %rax
and %rdx are used to return integer and pointer values. The registers %xmm0 and %xmm1 are used to return
floating point values.
Additional registers with assigned roles in the standard calling sequence:
%rsp
The stack pointer holds the limit of the current stack frame, which is the address of the stack’s bottommost, valid word. The stack must be 16-byte aligned.
%rbp
The frame pointer holds a base address for the current stack frame. Consequently, a function has registers
pointing to both ends of its frame. Incoming arguments reside in the previous frame, referenced as
positive offsets from %rbp, while local variables reside in the current frame, referenced as negative offsets
from %rbp. A function must preserve this register value for its caller.PGI® User’s Guide
280
RFLAGS
The flags register contains the system flags, such as the direction flag and the carry flag. The direction flag
must be set to the “forward” (i.e., zero) direction before entry and upon exit from a function. Other user
flags have no specified role in the standard calling sequence and are not preserved.
Floating Point Control Word
The control word contains the floating-point flags, such as the rounding mode and exception masking.
This register is initialized at process initialization time and its value must be preserved.
Signals can interrupt processes. Functions called during signal handling have no unusual restriction on their
use of registers. Moreover, if a signal handling function returns, the process resumes its original execution
path with registers restored to their original values. Thus, programs and compilers may freely use all registers
without danger of signal handlers changing their values.
Function Return Values
Functions Returning Scalars or No Value
• A function that returns an integral or pointer value places its result in the next available register of the
sequence %rax, %rdx.
• A function that returns a floating point value that fits in the XMM registers returns this value in the next
available XMM register of the sequence %xmm0, %xmm1.
• An X87 floating-point return value appears on the top of the floating point stack in %st(0) as an 80-bit X87
number. If this X87 return value is a complex number, the real part of the value is returned in %st(0) and
the imaginary part in %st(1).
• A function that returns a value in memory also returns the address of this memory in %rax.
• Functions that return no value (also called procedures or void functions) put no particular value in any
register.
Functions Returning Structures or Unions
A function can use either registers or memory to return a structure or union. The size and type of the structure
or union determine how it is returned. If a structure or union is larger than 16 bytes, it is returned in memory
allocated by the caller.
To determine whether a 16-byte or smaller structure or union can be returned in one or more return
registers, examine the first eight bytes of the structure or union. The type or types of the structure or union’s
fields making up these eight bytes determine how these eight bytes will be returned. If the eight bytes contain at
least one integral type, the eight bytes will be returned in %rax even if non-integral types are also present in the
eight bytes. If the eight bytes only contain floating point types, these eight bytes will be returned in %xmm0.
If the structure or union is larger than eight bytes but smaller than 17 bytes, examine the type or types of
the fields making up the second eight bytes of the structure or union. If these eight bytes contain at least one
integral type, these eight bytes will be returned in %rdx even if non-integral types are also present in the eight
bytes. If the eight bytes only contain floating point types, these eight bytes will be returned in %xmm1.Chapter 18. Run-time Environment
281
If a structure or union is returned in memory, the caller provides the space for the return value and passes its
address to the function as a “hidden” first argument in %rdi. This address will also be returned in %rax.
Argument Passing
Integral and Pointer Arguments
Integral and pointer arguments are passed to a function using the next available register of the sequence %rdi,
%rsi, %rdx, %rcx, %r8, %r9. After this list of registers has been exhausted, all remaining integral and pointer
arguments are passed to the function via the stack.
Floating-Point Arguments
Float and double arguments are passed to a function using the next available XMM register taken in the
order from %xmm0 to %xmm7. After this list of registers has been exhausted, all remaining float and double
arguments are passed to the function via the stack.
Structure and Union Arguments
Structure and union arguments can be passed to a function in either registers or on the stack. The size and
type of the structure or union determine how it is passed. If a structure or union is larger than 16 bytes, it is
passed to the function in memory.
To determine whether a 16-byte or smaller structure or union can be passed to a function in one or two
registers, examine the first eight bytes of the structure or union. The type or types of the structure or union’s
fields making up these eight bytes determine how these eight bytes will be passed. If the eight bytes contain
at least one integral type, the eight bytes will be passed in the first available general purpose register of the
sequence %rdi, %rsi, %rdx, %rcx, %r8, %r9 even if non-integral types are also present in the eight bytes. If the
eight bytes only contain floating point types, these eight bytes will be passed in the first available XMM register
of the sequence from %xmm0 to %xmm7.
If the structure or union is larger than eight bytes but smaller than 17 bytes, examine the type or types of the
fields making up the second eight bytes of the structure or union. If the eight bytes contain at least one integral
type, the eight bytes will be passed in the next available general purpose register of the sequence %rdi, %rsi,
%rdx, %rcx, %r8, %r9 even if non-integral types are also present in the eight bytes. If these eight bytes only
contain floating point types, these eight bytes will be passed in the next available XMM register of the sequence
from %xmm0 to %xmm7.
If the first or second eight bytes of the structure or union cannot be passed in a register for some reason, the
entire structure or union must be passed in memory.
Passing Arguments on the Stack
If there are arguments left after every argument register has been allocated, the remaining arguments are
passed to the function on the stack. The unassigned arguments are pushed on the stack in reverse order, with
the last argument pushed first.
Table 18.9, “Register Allocation for Example A-2” shows the register allocation and stack frame offsets for
the function declaration and call shown in the following example. Both table and example are adapted from
System V Application Binary Interface: AMD64 Architecture Processor Supplement.PGI® User’s Guide
282
Example 18.2. Parameter Passing
typedef struct {
int a, b;
double d;
} structparam;
structparam s;
int e, f, g, h, i, j, k;
float flt;
double m, n;
extern void func(int e, int f, structparam s, int g, int h,
float flt, double m, double n, int i, int j, int k);
void func2()
{
func(e, f, s, g, h, flt, m, n, i, j, k);
}
Table 18.9. Register Allocation for Example A-2
General Purpose
Registers
Floating Point
Registers
Stack Frame Offset
%rdi: e %xmm0: s.d 0: j
%rsi: f %xmm1: flt 8: k
%rdx: s.a,s.b %xmm2: m
%rcx: g %xmm3: n
%r8: h
%r9: i
Implementing a Stack
In general, compilers and programmers must maintain a software stack. The stack pointer, register %rsp, is
set by the operating system for the application when the program is started. The stack must grow downwards
from high addresses.
A separate frame pointer enables calls to routines that change the stack pointer to allocate space on the stack
at run-time (e.g. alloca). Some languages can also return values from a routine allocated on stack space
below the original top-of-stack pointer. Such a routine prevents the calling function from using %rsp-relative
addressing for values on the stack. If the compiler does not call routines that leave %rsp in an altered state
when they return, a frame pointer is not needed and may not be used if the compiler option –Mnoframe is
specified.
The stack must be kept aligned on 16-byte boundaries.
Variable Length Parameter Lists.
Parameter passing in registers can handle a variable number of parameters. The C language uses a special
method to access variable-count parameters. The stdarg.h and varargs.h files define several functions to access
these parameters. A C routine with variable parameters must use the va_start macro to set up a data structure
before the parameters can be used. The va_arg macro must be used to access the successive parameters.Chapter 18. Run-time Environment
283
For calls that use varargs or stdargs, the register %rax acts as a hidden argument whose value is the number of
XMM registers used in the call.
C Parameter Conversion.
In C, for a called prototyped function, the parameter type in the called function must match the argument
type in the calling function. If the called function is not prototyped, the calling convention uses the types of
the arguments but promotes char or short to int, and unsigned char or unsigned short to unsigned int and
promotes float to double, unless you use the ##Msingle option. For more information on the –Msingle option,
refer to Chapter 3.
Calling Assembly Language Programs
Example 18.3. C Program Calling an Assembly-language Routine
/* File: testmain.c */
#include
int
main() {
long l_para1 = 2;
float f_para2 = 1.0;
double d_para3 = 0.5;
float f_return;
extern float sum_3(long para1, float para2, double para3);
f_return = sum_3(l_para1, f_para2, d_para3);
printf("Parameter one, type long = %ld\n", l_para1);
printf("Parameter two, type float = %f\n", f_para2);
printf("Parameter three, type double = %f\n", d_para3);
printf("The sum after conversion = %f\n", f_return);
return 0;
}
# File: sum_3.s
# Computes ( para1 + para2 ) + para3
.text
.align 16
.globl sum_3
sum_3:
pushq %rbp
movq %rsp, %rbp
cvtsi2ssq %rdi, %xmm2
addss %xmm0, %xmm2
cvtss2sd %xmm2,%xmm2
addsd %xmm1, %xmm2
cvtsd2ss %xmm2, %xmm2
movaps %xmm2, %xmm0
popq %rbp
ret
.type sum_3, @function
.size sum_3,.-sum_3
Linux86-64 Fortran Supplement
Sections A2.4.1 through A2.4.4 define the Fortran supplement to the ABI for x64 Linux. The register usage
conventions set forth in that document remain the same for Fortran.PGI® User’s Guide
284
Fortran Fundamental Types
Table 18.10. Linux86-64 Fortran Fundamental Types
Fortran Type Size
(bytes)
Alignment
(bytes)
INTEGER 4 4
INTEGER*1 1 1
INTEGER*2 2 2
INTEGER*4 4 4
INTEGER*8 8 8
LOGICAL 4 4
LOGICAL*1 1 1
LOGICAL*2 2 2
LOGICAL*4 4 4
LOGICAL*8 8 8
BYTE 1 1
CHARACTER*n n 1
REAL 4 4
REAL*4 4 4
REAL*8 8 8
DOUBLE PRECISION 8 8
COMPLEX 8 4
COMPLEX*8 8 4
COMPLEX*16 16 8
DOUBLE COMPLEX 16 8
A logical constant is one of:
• .TRUE.
• .FALSE.
The logical constants .TRUE. and .FALSE. are defined to be the four-byte values -1 and 0 respectively. A logical
expression is defined to be .TRUE. if its least significant bit is 1 and .FALSE. otherwise.
Note that the value of a character is not automatically NULL-terminated.
Naming Conventions
By default, all globally visible Fortran symbol names (subroutines, functions, common blocks) are converted
to lower-case. In addition, an underscore is appended to Fortran global names to distinguish the Fortran name
space from the C/C++ name space.Chapter 18. Run-time Environment
285
Argument Passing and Return Conventions
Arguments are passed by reference (i.e. the address of the argument is passed, rather than the argument
itself). In contrast, C/C++ arguments are passed by value.
When passing an argument declared as Fortran type CHARACTER, an argument representing the length of the
CHARACTER argument is also passed to the function. This length argument is a four-byte integer passed by
value, and is passed at the end of the parameter list following the other formal arguments. A length argument is
passed for each CHARACTER argument; the length arguments are passed in the same order as their respective
CHARACTER arguments.
A Fortran function, returning a value of type CHARACTER, adds two arguments to the beginning of its argument
list. The first additional argument is the address of the area created by the caller for the return value; the
second additional argument is the length of the return value. If a Fortran function is declared to return a
character value of constant length, for example CHARACTER*4 FUNCTION CHF(), the second extra parameter
representing the length of the return value must still be supplied.
A Fortran complex function returns its value in memory. The caller provides space for the return value and
passes the address of this storage as if it were the first argument to the function.
Alternate return specifiers of a Fortran function are not passed as arguments by the caller. The alternate return
function passes the appropriate return value back to the caller in %rax.
The handling of the following Fortran 90 features is implementation-defined: internal procedures, pointer
arguments, assumed-shape arguments, functions returning arrays, and functions returning derived types.
Inter-language Calling
Inter-language calling between Fortran and C/C++ is possible if function/subroutine parameters and return
values match types. If a C/C++ function returns a value, call it from Fortran as a function, otherwise, call it as
a subroutine. If a Fortran function has type CHARACTER or COMPLEX, call it from C/C++ as a void function.
If a Fortran subroutine has alternate returns, call it from C/C++ as a function returning int; the value of such
a subroutine is the value of the integer expression specified in the alternate RETURN statement. If a Fortran
subroutine does not contain alternate returns, call it from C/C++ as a void function.
The following table provides the C/C++ data type corresponding to each Fortran data type.
Table 18.11. Fortran and C/C++ Data Type Compatibility
Fortran Type C/C++ Type Size (bytes)
CHARACTER*n x char x[n] n
REAL x float x 4
REAL*4 x float x 4
REAL*8 x double x 8
DOUBLE PRECISION x double x 8
INTEGER x int x 4
INTEGER*1 x signed char x 1PGI® User’s Guide
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Fortran Type C/C++ Type Size (bytes)
INTEGER*2 x short x 2
INTEGER*4 x int x 4
INTEGER*8 x long x, or long long x 8
LOGICAL x int x 4
LOGICAL*1 x char x 1
LOGICAL*2 x short x 2
LOGICAL*4 x int x 4
LOGICAL*8 x long x, or long long x 8
Table 18.12. Fortran and C/C++ Representation of the COMPLEX Type
Fortran Type (lower case) C/C++ Type Size (bytes)
complex x struct {float r,i;} x; 8
float complex x;
complex*8 x struct {float r,i;} x; 8
float complex x; 8
double complex x struct {double dr,di;} x; 16
double complex x; 16
complex *16 x struct {double dr,di;} x; 16
double complex x; 16
Note
For C/C++, the complex type implies C99 or later.
Arrays
C/C++ arrays and Fortran arrays use different default initial array index values. By default, C/C++ arrays start
at 0 and Fortran arrays start at 1. A Fortran array can be declared to start at zero.
Another difference between Fortran and C/C++ arrays is the storage method used. Fortran uses columnmajor order and C/C++ use row-major order. For one-dimensional arrays, this poses no problems. For
two-dimensional arrays, where there are an equal number of rows and columns, row and column indexes
can simply be reversed. Inter-language function mixing is not recommended for arrays other than single
dimensional arrays and square two-dimensional arrays.
Structures, Unions, Maps, and Derived Types.
Fields within Fortran structures and derived types, and multiple map declarations within a Fortran union,
conform to the same alignment requirements used by C structures.Chapter 18. Run-time Environment
287
Common Blocks.
A named Fortran common block can be represented in C/C++ by a structure whose members correspond to
the members of the common block. The name of the structure in C/C++ must have the added underscore. For
example, the Fortran common block:
INTEGER I, J
COMPLEX C
DOUBLE COMPLEX CD
DOUBLE PRECISION D
COMMON /COM/ i, j, c, cd, d
is represented in C with the following equivalent:
extern struct {
int i;
int j;
struct {float real, imag;} c;
struct {double real, imag;} cd;
double d;
} com_;
and in C++ with the following equivalent:
extern "C" struct {
int i;
int j;
struct {float real, imag;} c;
struct {double real, imag;} cd;
double d;
} com_;
Note that the compiler-provided name of the BLANK COMMON block is implementation specific.
Calling Fortran COMPLEX and CHARACTER functions from C/C++ is not as straightforward as calling other
types of Fortran functions. Additional arguments must be passed to the Fortran function by the C/C++ caller. A
Fortran COMPLEX function returns its value in memory; the first argument passed to the function must contain
the address of the storage for this value. A Fortran CHARACTER function adds two arguments to the beginning
of its argument list. The following example of calling a Fortran CHARACTER function from C/C++ illustrates
these caller-provided extra parameters:
CHARACTER*(*) FUNCTION CHF(C1, I)
CHARACTER*(*) C1
INTEGER I
END
extern void chf_();
char tmp[10];
char c1[9];
int i;
chf_(tmp, 10, c1, &i, 9);
The extra parameters tmp and 10 are supplied for the return value, while 9 is supplied as the length of c1.
Refer to Section 2.8, Argument Passing and Return Conventions, for additional information.
Win64 Programming Model
This section defines compiler and assembly language conventions for the use of certain aspects of an x64
processor running a Win64 operating system, including SUA64. These standards must be followed to guarantee
that compilers, application programs, and operating systems written by different people and organizationsPGI® User’s Guide
288
will work together. The conventions supported by the PGCC ANSI C compiler implement the application binary
interface (ABI) as defined in the AMD64 Software Conventions document.
Function Calling Sequence
This section describes the standard function calling sequence, including the stack frame, register usage, and
parameter passing.
Register Usage Conventions.
The following table defines the standard for register allocation. The 64-bit AMD64 and EM64T Architectures
provide a number of registers. All the general purpose registers, XMM registers, and x87 registers are global to
all procedures in a running program.
Table 18.13. Register Allocation
Type Name Purpose
General %rax return value register
%rbx callee-saved
%rcx pass 1st argument to functions
%rdx pass 2nd argument to functions
%rsp stack pointer
%rbp callee-saved; optional stack frame pointer
%rsi callee-saved
%rdi callee-saved
%r8 pass 3rd argument to functions
%r9 pass 4th argument to functions
%r10-%r11 temporary registers; used in syscall/sysret instructions
%r12-r15 callee-saved registers
XMM %xmm0 pass 1st floating point argument; return value register
%xmm1 pass 2nd floating point argument
%xmm2 pass 3rd floating point argument
%xmm3 pass 4th floating point argument
%xmm4-%xmm5 temporary registers
%xmm6-%xmm15 callee-saved registers
In addition to the registers, each function has a frame on the run-time stack. This stack grows downward from
high addresses. The next table shows the stack frame organization.
Table 18.14. Standard Stack Frame
Position Contents Frame
8n-120 (%rbp) argument eightbyte n previousChapter 18. Run-time Environment
289
Position Contents Frame
. . .
-80 (%rbp) argument eightbyte 5
-88 (%rbp) %r9 home
-96 (%rbp) %r8 home
-104 (%rbp) %rdx home
-112 (%rbp) %rcx home
-120 (%rbp) return address current
-128 (%rbp) caller's %rbp
. . .
0 (%rsp) variable size
Key points concerning the stack frame:
• The parameter area at the bottom of the stack must contain enough space to hold all the parameters needed
by any function call. Space must be set aside for the four register parameters to be “homed” to the stack
even if there are less than four register parameters used in a given call.
• Sixteen-byte alignment of the stack is required except within a function’s prolog and within leaf functions.
All registers on an x64 system are global and thus visible to both a calling and a called function. Registers
%rbx, %rsp, %rbp, %rsi, %rdi, %r12, %r13, %r14, and %r15 are non-volatile. Therefore, a called function
must preserve these registers’ values for its caller. Remaining registers are scratch. If a calling function wants
to preserve such a register value across a function call, it must save a value in its local stack frame.
Registers are used in the standard calling sequence. The first four arguments are passed in registers. Integral
and pointer arguments are passed in these general purpose registers (listed in order): %rcx, %rdx, %r8, %r9.
Floating point arguments are passed in the first four XMM registers: %xmm0, %xmm1, %xmm2, %xmm3.
Registers are assigned using the argument’s ordinal position in the argument list. For example, if a function’s
first argument is an integral type and its second argument is a floating-point type, the first argument will be
passed in the first general purpose register (%rcx) and the second argument will be passed in the second
XMM register (%xmm1); the first XMM register and second general purpose register are ignored. Arguments
after the first four are passed on the stack.
Integral and pointer type return values are returned in %rax. Floating point return values are returned in
%xmm0.
Additional registers with assigned roles in the standard calling sequence:
%rsp
The stack pointer holds the limit of the current stack frame, which is the address of the stack’s bottommost, valid word. The stack pointer should point to a 16-byte aligned area unless in the prolog or a leaf
function.PGI® User’s Guide
290
%rbp
The frame pointer, if used, can provide a way to reference the previous frame on the stack. Details are
implementation dependent. A function must preserve this register value for its caller.
MXCSR
The flags register MXCSR contains the system flags, such as the direction flag and the carry flag. The six
status flags (MXCSR[0:5]) are volatile; the remainder of the register is nonvolatile.
x87
Floating Point Control Word (FPCSR) The control word contains the floating-point flags, such as the
rounding mode and exception masking. This register is initialized at process initialization time and its
value must be preserved.
Signals can interrupt processes. Functions called during signal handling have no unusual restriction on their
use of registers. Moreover, if a signal handling function returns, the process resumes its original execution
path with registers restored to their original values. Thus, programs and compilers may freely use all registers
without danger of signal handlers changing their values.
Function Return Values
Functions Returning Scalars or No Value
• A function that returns an integral or pointer value that fits in 64 bits places its result in %rax.
• A function that returns a floating point value that fits in the XMM registers returns this value in %xmm0.
• A function that returns a value in memory via the stack places the address of this memory (passed to the
function as a “hidden” first argument in %rcx) in %rax.
• Functions that return no value (also called procedures or void functions) put no particular value in any
register.
• A call instruction pushes the address of the next instruction (the return address) onto the stack. The return
instruction pops the address off the stack and effectively continues execution at the next instruction after the
call instruction. A function that returns a scalar or no value must preserve the caller's registers as described
above. Additionally, the called function must remove the return address from the stack, leaving the stack
pointer (%rsp) with the value it had before the call instruction was executed.
Functions Returning Structures or Unions
A function can use either registers or the stack to return a structure or union. The size and type of the
structure or union determine how it is returned. A structure or union is returned in memory if it is larger than
8 bytes or if its size is 3, 5, 6, or 7 bytes. A structure or union is returned in %rax if its size is 1, 2, 4, or 8
bytes.
If a structure or union is to be returned in memory, the caller provides space for the return value and passes
its address to the function as a “hidden” first argument in %rcx. This address will also be returned in %rax.Chapter 18. Run-time Environment
291
Argument Passing
Integral and Pointer Arguments
Integral and pointer arguments are passed to a function using the next available register of the sequence %rcx,
%rdx, %r8, %r9. After this list of registers has been exhausted, all remaining integral and pointer arguments
are passed to the function via the stack.
Floating-Point Arguments
Float and double arguments are passed to a function using the next available XMM register of the sequence
%xmm0, %xmm1, %xmm2, %xmm3. After this list of registers has been exhausted, all remaining XMM
floating-point arguments are passed to the function via the stack.
Array, Structure, and Union Arguments
Arrays and strings are passed to functions using a pointer to caller-allocated memory.
Structure and union arguments of size 1, 2, 4, or 8 bytes will be passed as if they were integers of the same
size. Structures and unions of other sizes will be passed as a pointer to a temporary, allocated by the caller,
and whose value contains the value of the argument. The caller-allocated temporary memory used for
arguments of aggregate type must be 16-byte aligned.
Passing Arguments on the Stack
Registers are assigned using the argument’s ordinal position in the argument list. For example, if a function’s
first argument is an integral type and its second argument is a floating-point type, the first argument will be
passed in the first general purpose register (%rcx) and the second argument will be passed in the second
XMM register (%xmm1); the first XMM register and second general purpose register are ignored. Arguments
after the first four are passed on the stack; they are pushed on the stack in reverse order, with the last
argument pushed first.
Table 18.15, “Register Allocation for Example A-4” shows the register allocation and stack frame offsets for the
function declaration and call shown in the following example.
Example 18.4. Parameter Passing
typedef struct {
int i;
float f;
} struct1;
int i;
float f;
double d;
long l;
long long ll;
struct1 s1;
extern void func (int i, float f, struct1 s1, double d,
long long ll, long l);
func (i, f, s1, d, ll, l);PGI® User’s Guide
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Table 18.15. Register Allocation for Example A-4
General Purpose
Registers
Floating Point
Registers
Stack Frame Offset
%rcx: i %xmm0: 32: ll
%rdx: %xmm1: f 40: l
%r8: s1.i, s1.f %xmm2:
%r9: %xmm3: d
Implementing a Stack
In general, compilers and programmers must maintain a software stack. The stack pointer, register %rsp, is
set by the operating system for the application when the program is started. The stack must grow downwards
from high addresses.
A separate frame pointer enables calls to routines that change the stack pointer to allocate space on the stack
at run-time (e.g. alloca). Some languages can also return values from a routine allocated on stack space
below the original top-of-stack pointer. Such a routine prevents the calling function from using %rsp-relative
addressing to get at values on the stack. If the compiler does not call routines that leave %rsp in an altered
state when they return, a frame pointer is not needed and is not used if the compiler option –Mnoframe is
specified.
The stack must always be 16-byte aligned except within the prolog and within leaf functions.
Variable Length Parameter Lists.
Parameter passing in registers can handle a variable number of parameters. The C language uses a special
method to access variable-count parameters. The stdarg.h and varargs.h files define several functions to access
these parameters. A C routine with variable parameters must use the va_start macro to set up a data structure
before the parameters can be used. The va_arg macro must be used to access the successive parameters.
For unprototyped functions or functions that use varargs, floating-point arguments passed in registers must be
passed in both an XMM register and its corresponding general purpose register.
C Parameter Conversion.
In C, for a called prototyped function, the parameter type in the called function must match the argument
type in the calling function. If the called function is not prototyped, the calling convention uses the types of
the arguments but promotes char or short to int, and unsigned char or unsigned short to unsigned int and
promotes float to double, unless you use the –Msingle option. For more information on the –Msingle option,
refer to Chapter 3. If the called function is prototyped, the unused bits of a register containing a char or short
parameter are undefined and the called function must extend the sign of the unused bits when needed.Chapter 18. Run-time Environment
293
Calling Assembly Language Programs
Example 18.5. C Program Calling an Assembly-language Routine
/* File: testmain.c */
main() {
long l_para1 = 0x3f800000;
float f_para2 = 1.0;
double d_para3 = 0.5;
float f_return;
extern float sum_3 (long para1, float para2, double para3);
f_return = sum_3(l_para1,f_para2, d_para3);
printf("Parameter one, type long = %08x\n",l_para1);
printf("Parameter two, type float = %f\n",f_para2);
printf("Parameter three, type double = %g\n",d_para3);
printf("The sum after conversion = %f\n",f_return);
}
# File: sum_3.s
# Computes ( para1 + para2 ) + para3
.text
.align 16
.globl sum_3
sum_3:
pushq %rbp
leaq 128(%rsp), %rbp
cvtsi2ss %ecx, %xmm0
addss %xmm1, %xmm0
cvtss2sd %xmm0, %xmm0
addsd %xmm2, %xmm0
cvtsd2ss %xmm0, %xmm0
popq %rbp
ret
.type sum_3,@function
.size sum_3,.-sum_3
Win64/SUA64 Fortran Supplement
Sections A3.4.1 through A3.4.4 define the Fortran supplement to the AMD64 Software Conventions for Win64.
The register usage conventions set forth in that document remain the same for Fortran.
Fortran Fundamental Types
Table 18.16. Win64 Fortran Fundamental Types
Fortran Type Size
(bytes)
Alignment
(bytes)
INTEGER 4 4
INTEGER*1 1 1
INTEGER*2 2 2
INTEGER*4 4 4
INTEGER*8 8 8
LOGICAL 4 4PGI® User’s Guide
294
Fortran Type Size
(bytes)
Alignment
(bytes)
LOGICAL*1 1 1
LOGICAL*2 2 2
LOGICAL*4 4 4
LOGICAL*8 8 8
BYTE 1 1
CHARACTER*n n 1
REAL 4 4
REAL*4 4 4
REAL*8 8 8
DOUBLE PRECISION 8 8
COMPLEX 8 4
COMPLEX*8 8 4
COMPLEX*16 16 8
DOUBLE COMPLEX 16 8
A logical constant is one of:
• .TRUE.
• .FALSE.
The logical constants .TRUE. and .FALSE. are defined to be the four-byte values -1 and 0 respectively. A logical
expression is defined to be .TRUE. if its least significant bit is 1 and .FALSE. otherwise.
Note that the value of a character is not automatically NULL-terminated.
Fortran Naming Conventions
By default, all globally visible Fortran symbol names (subroutines, functions, common blocks) are converted
to lower-case. In addition, an underscore is appended to Fortran global names to distinguish the Fortran name
space from the C/C++ name space.
Fortran Argument Passing and Return Conventions
Arguments are passed by reference (i.e. the address of the argument is passed, rather than the argument
itself). In contrast, C/C++ arguments are passed by value.
When passing an argument declared as Fortran type CHARACTER, an argument representing the length of the
CHARACTER argument is also passed to the function. This length argument is a four-byte integer passed by
value, and is passed at the end of the parameter list following the other formal arguments. A length argument is
passed for each CHARACTER argument; the length arguments are passed in the same order as their respective
CHARACTER arguments.Chapter 18. Run-time Environment
295
A Fortran function, returning a value of type CHARACTER, adds two arguments to the beginning of its argument
list. The first additional argument is the address of the area created by the caller for the return value; the
second additional argument is the length of the return value. If a Fortran function is declared to return a
character value of constant length, for example CHARACTER*4 FUNCTION CHF(), the second extra parameter
representing the length of the return value must still be supplied.
A Fortran complex function returns its value in memory. The caller provides space for the return value and
passes the address of this storage as if it were the first argument to the function.
Alternate return specifiers of a Fortran function are not passed as arguments by the caller. The alternate return
function passes the appropriate return value back to the caller in %rax.
The handling of the following Fortran 90 features is implementation-defined: internal procedures, pointer
arguments, assumed-shape arguments, functions returning arrays, and functions returning derived types.
Inter-language Calling
Inter-language calling between Fortran and C/C++ is possible if function/subroutine parameters and return
values match types. If a C/C++ function returns a value, call it from Fortran as a function, otherwise, call it as
a subroutine. If a Fortran function has type CHARACTER or COMPLEX, call it from C/C++ as a void function.
If a Fortran subroutine has alternate returns, call it from C/C++ as a function returning int; the value of such
a subroutine is the value of the integer expression specified in the alternate RETURN statement. If a Fortran
subroutine does not contain alternate returns, call it from C/C++ as a void function.
The following table provides the C/C++ data type corresponding to each Fortran data type.
Table 18.17. Fortran and C/C++ Data Type Compatibility
Fortran Type C/C++ Type Size (bytes)
CHARACTER*n x char x[n] n
REAL x float x 4
REAL*4 x float x 4
REAL*8 x double x 8
DOUBLE PRECISION x double x 8
INTEGER x int x 4
INTEGER*1 x signed char x 1
INTEGER*2 x short x 2
INTEGER*4 x int x 4
INTEGER*8 x long long x 8
LOGICAL x int x 4
LOGICAL*1 x char x 1
LOGICAL*2 x short x 2
LOGICAL*4 x int x 4PGI® User’s Guide
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Fortran Type C/C++ Type Size (bytes)
LOGICAL*8 x long long x 8
Table 18.18. Fortran and C/C++ Representation of the COMPLEX Type
Fortran Type (lower case) C/C++ Type Size (bytes)
complex x struct {float r,i;} x; 8
float complex x;
complex*8 x struct {float r,i;} x; 8
float complex x; 8
double complex x struct {double dr,di;} x; 16
double complex x; 16
complex *16 x struct {double dr,di;} x; 16
double complex x; 16
Note
For C/C++, the complex type implies C99 or later.
Arrays
C/C++ arrays and Fortran arrays use different default initial array index values. By default, C/C++ arrays start
at 0 and Fortran arrays start at 1. A Fortran array can be declared to start at zero.
Another difference between Fortran and C/C++ arrays is the storage method used. Fortran uses columnmajor order and C/C++ use row-major order. For one-dimensional arrays, this poses no problems. For
two-dimensional arrays, where there are an equal number of rows and columns, row and column indexes
can simply be reversed. Inter-language function mixing is not recommended for arrays other than single
dimensional arrays and square two-dimensional arrays.
Structures, Unions, Maps, and Derived Types.
Fields within Fortran structures and derived types, and multiple map declarations within a Fortran union,
conform to the same alignment requirements used by C structures.
Common Blocks.
A named Fortran common block can be represented in C/C++ by a structure whose members correspond to
the members of the common block. The name of the structure in C/C++ must have the added underscore. For
example, the Fortran common block:
INTEGER I, J
COMPLEX C
DOUBLE COMPLEX CD
DOUBLE PRECISION D
COMMON /COM/ i, j, c, cd, dChapter 18. Run-time Environment
297
is represented in C with the following equivalent:
extern struct {
int i;
int j;
struct {float real, imag;} c;
struct {double real, imag;} cd;
double d;
} com_;
and in C++ with the following equivalent:
extern "C" struct {
int i;
int j;
struct {float real, imag;} c;
struct {double real, imag;} cd;
double d;
} com_;
Note that the compiler-provided name of the BLANK COMMON block is implementation specific.
Calling Fortran COMPLEX and CHARACTER functions from C/C++ is not as straightforward as calling other
types of Fortran functions. Additional arguments must be passed to the Fortran function by the C/C++ caller. A
Fortran COMPLEX function returns its value in memory; the first argument passed to the function must contain
the address of the storage for this value. A Fortran CHARACTER function adds two arguments to the beginning
of its argument list. The following example of calling a Fortran CHARACTER function from C/C++ illustrates
these caller-provided extra parameters:
CHARACTER*(*) FUNCTION CHF(C1, I)
CHARACTER*(*) C1
INTEGER I
END
extern void chf_();
char tmp[10];
char c1[9];
int i;
chf_(tmp, 10, c1, &i, 9);
The extra parameters tmp and 10 are supplied for the return value, while 9 is supplied as the length of c1.
Refer to “Argument Passing and Return Values,” on page 113, for additional information.298299
Chapter 19. C++ Dialect Supported
The PGC++ compiler accepts the C++ language of the ISO/IEC 14882:1998 C++ standard, except for
Exported Templates.PGC++ optionally accepts a number of features erroneously accepted by cfront version
2.1 or 3.0. Using the -b option, PGC++ accepts these features, which may never have been legal C++, but have
found their way into some user’s code.
Command-line options provide full support of many C++ variants, including strict standard conformance.
PGC++ provides command line options that enable the user to specify whether anachronisms and/or cfront
2.1/3.0 compatibility features should be accepted.
Extensions Accepted in Normal C++ Mode
The following extensions are accepted in all modes (except when strict ANSI violations are diagnosed as
errors, see the –A option):
• A friend declaration for a class may omit the class keyword:
class A {
friend B; // Should be "friend class B"
};
• Constants of scalar type may be defined within classes:
class A {
const int size = 10;
int a[size];
};
• In the declaration of a class member, a qualified name may be used:
struct A{
int A::f(); // Should be int f();
}
• The preprocessing symbol c_plusplus is defined in addition to the standard __cplusplus.
• An assignment operator declared in a derived class with a parameter type matching one of its base classes
is treated as a "default'' assignment operator --- that is, such a declaration blocks the implicit generation of
a copy assignment operator. (This is cfront behavior that is known to be relied upon in at least one widely
used library.) Here's an example:
struct A { } ;PGI® User’s Guide
300
struct B : public A {
B& operator=(A&);
};
• By default, as well as in cfront-compatibility mode, there will be no implicit declaration of
B::operator=(const B&), whereas in strict-ANSI mode B::operator=(A&) is not a copy assignment operator
and B::operator=(const B&) is implicitly declared.
• Implicit type conversion between a pointer to an extern “C” function and a pointer to an extern “C++”
function is permitted. Here’s an example:
extern "C" void
f(); // f’s type has extern "C" linkage
void (*pf) () // pf points to an extern
"C++" function
= &f; // error unless
implicit conv is allowed
cfront 2.1 Compatibility Mode
The following extensions are accepted in cfront 2.1 compatibility mode in addition to the extensions listed in
the following 2.1/3.0 section (i.e., these are things that were corrected in the 3.0 release of cfront):
• The dependent statement of an if, while, do-while, or for is not considered to define a scope. The dependent
statement may not be a declaration. Any objects constructed within the dependent statement are destroyed
at exit from the dependent statement.
• Implicit conversion from integral types to enumeration types is allowed.
• A non-const member function may be called for a const object. A warning is issued.
• A const void * value may be implicitly converted to a void * value, e.g., when passed as an argument.
• When, in determining the level of argument match for overloading, a reference parameter is initialized
from an argument that requires a non-class standard conversion, the conversion counts as a user-defined
conversion. (This is an outright bug, which unfortunately happens to be exploited in some class libraries.)
• When a builtin operator is considered alongside overloaded operators in overload resolution, the match
of an operand of a builtin type against the builtin type required by the builtin operator is considered a
standard conversion in all cases (e.g., even when the type is exactly right without conversion).
• A reference to a non-const type may be initialized from a value that is a const-qualified version of the same
type, but only if the value is the result of selecting a member from a const class object or a pointer to such
an object.
• A cast to an array type is allowed; it is treated like a cast to a pointer to the array element type. A warning is
issued.
• When an array is selected from a class, the type qualifiers on the class object (if any) are not preserved in
the selected array. (In the normal mode, any type qualifiers on the object are preserved in the element type
of the resultant array.)
• An identifier in a function is allowed to have the same name as a parameter of the function. A warning is
issued.Chapter 19. C++ Dialect Supported
301
• An expression of type void may be supplied on the return statement in a function with a void return type. A
warning is issued.
• cfront has a bug that causes a global identifier to be found when a member of a class or one of its base
classes should actually be found. This bug is not emulated in cfront compatibility mode.
• A parameter of type "const void *'' is allowed on operator delete; it is treated as equivalent to "void *".
• A period (".") may be used for qualification where "::" should be used. Only "::'' may be used as a global
qualifier. Except for the global qualifier, the two kinds of qualifier operators may not be mixed in a given
name (i.e., you may say A::B::C or A.B.C but not A::B.C or A.B::C). A period may not be used in a vacuous
destructor reference nor in a qualifier that follows a template reference such as A::B.
• cfront 2.1 does not correctly look up names in friend functions that are inside class definitions. In this
example function f should refer to the functions and variables (e.g., f1 and a1) from the class declaration.
Instead, the global definitions are used.
int a1;
int e1;
void f1();
class A {
int a1;
void f1();
friend void f()
{
int i1 = a1; // cfront uses global a1
f1(); // cfront uses global f1
}
};
• Only the innermost class scope is (incorrectly) skipped by cfront as illustrated in the following example.
int a1;
int b1;
struct A {
static int a1;
class B {
static int b1;
friend void f()
{
int i1 = a1; // cfront uses A::a1
int j1 = b1; // cfront uses global b1
}
};
};
• operator= may be declared as a nonmember function. (This is flagged as an anachronism by cfront 2.1)
• A type qualifier is allowed (but ignored) on the declaration of a constructor or destructor. For example:
class A {
A() const; // No error in cfront 2.1 mode
};
cfront 2.1/3.0 Compatibility Mode
The following extensions are accepted in both cfront 2.1 and cfront 3.0 compatibility mode (i.e., these are
features or problems that exist in both cfront 2.1 and 3.0):PGI® User’s Guide
302
• Type qualifiers on the this parameter may to be dropped in contexts such as this example:
struct
A {
void f() const;
};
void (A::*fp)() = &A::f;
This is actually a safe operation. A pointer to a const function may be put into a pointer to non-const,
because a call using the pointer is permitted to modify the object and the function pointed to will actually
not modify the object. The opposite assignment would not be safe.
• Conversion operators specifying conversion to void are allowed.
• A nonstandard friend declaration may introduce a new type. A friend declaration that omits the elaborated
type specifier is allowed in default mode, but in cfront mode the declaration is also allowed to introduce a
new type name.
struct A {
friend B;
};
• The third operator of the ? operator is a conditional expression instead of an assignment expression.
• A reference to a pointer type may be initialized from a pointer value without use of a temporary even when
the reference pointer type has additional type qualifiers above those present in the pointer value. For
example,
int *p;
const int *&r = p; // No
temporary used
• A reference may be initialized with a null.303
Chapter 20. C/C++ MMX/SSE Inline
Intrinsics
An intrinsic is a function available in a given language whose implementation is handled specifically by the
compiler. Typically, an intrinsic substitutes a sequence of automatically-generated instructions for the original
function call. Since the compiler has an intimate knowledge of the intrinsic function, it can better integrate it
and optimize it for the situation.
PGI provides support for MMX and SSE/SSE2/SSE3/SSSE3/SSE4a/ABM intrinsics in C/C++ programs. The
definitions of the intrinsics are in the inline library libintrinsics.il, which is automatically included in your
compilation.
Intrinsics make the use of processor-specific enhancements easier because they provide a C/C++ language
interface to assembly instructions. In doing so, the compiler manages things that the user would normally have
to be concerned with, such as register names, register allocations, and memory locations of data.
This chapter contains these seven tables associated with inline intrinsics:
• A table of MMX inline intrinsics (mmintrin.h)
• A table of SSE inline intrinsics (xmmintrin.h)
• A table of SSE2 inline intrinsics (emmintrin.h)
• A table of SSE3 inline intrinsics (pmmintrin.h)
• A table of SSSE3 inline intrinsics (tmmintrin.h)
• A table of SSE4a inline intrinsics (ammintrin.h)
• A table of ABM inline intrinsics (intrin.h)
Using Intrinsic functions
The definitions of the intrinsics are provided in the inline library libintrinsics.il., which is
automatically included when you compile.PGI® User’s Guide
304
Required Header File
To call these intrinsic functions from a C/C++ source, you must include the corresponding header file - one of
the following:
• For MMX, use mmintrin.h
• For SSE, use xmmintrin.h
• For SSE2, use emmintrin.h
• For SSE3, use pmmintrin.h
• For SSSE3 use tmmintrin.h
• For SSE4a use ammintrin.h
• For ABM use intrin.h
Intrinsic Data Types
The following table describes the data types that are defined for intrinsics:
Data Types Defined in Description
__m64 mmintrin.h For use with MMX intrinsics, this 64-bit data type stores one 64-bit
or two 32-bit integer values.
__m128 xmmintrin.h For use with SSE intrinsics, this 128-bit data type, aligned on 16-byte
boundaries, stores four single-precision floating point values.
__m128d emmintrin.h For use with SSE2/SSE3 intrinsics, this 128-bit data type, aligned
on 16-byte boundaries, stores two double-precision floating point
values.
__m128i emmintrin.h For use with SSE2/SSE3 intrinsics, this 128-bit data type, aligned on
16-byte boundaries, stores two 64-bit integer values.
Intrinsic Example
The MMX/SSE intrinsics include functions for initializing variables of the types defined in the preceding table.
The following sample program, example.c, illustrates the use of the SSE intrinsics _mm_add_ps and
_mm_set_ps.
#include
int main(){
__m128 A, B, result;
A = _mm_set_ps(23.3, 43.7, 234.234, 98.746); /* initialize A */
B = _mm_set_ps(15.4, 34.3, 4.1, 8.6); /* initialize B */
result = _mm_add_ps(A, B);
return 0;
}
To compile this program, use the following command:
$ pgcc example.c -o myprog
The inline library libintrinsics.il is automatically inlined.Chapter 20. C/C++ MMX/SSE Inline Intrinsics
305
MMX Intrinsics
PGI supports a set of MMX Intrinsics which allow the use of the MMX instructions directly from C/C++ code,
without writing the assembly instructions. The following table lists the MMX intrinsics that PGI supports.
Note
Intrinsics with a * are only available on 64-bit systems.
Table 20.1. MMX Intrinsics (mmintrin.h)
_mm_empty _m_paddd _m_psllw _m_pand
_m_empty _mm_add_si64 _mm_slli_pi16 _mm_andnot_si64
_mm_cvtsi32_si64 _mm_adds_pi8 _m_psllwi _m_pandn
_m_from_int _m_paddsb _mm_sll_pi32 _mm_or_si64
_mm_cvtsi64x_si64* _mm_adds_pi16 _m_pslld _m_por
_mm_set_pi64x* _m_paddsw _mm_slli_pi32 _mm_xor_si64
_mm_cvtsi64_si32 _mm_adds_pu8 _m_pslldi _m_pxor
_m_to_int _m_paddusb _mm_sll_si64 _mm_cmpeq_pi8
_mm_cvtsi64_si64x* _mm_adds_pu16 _m_psllq _m_pcmpeqb
_mm_packs_pi16* _m_paddusw _mm_slli_si64 _mm_cmpgt_pi8
_m_packsswb _mm_sub_pi8 _m_psllqi _m_pcmpgtb
_mm_packs_pi32 _m_psubb _mm_sra_pi16 _mm_cmpeq_pi16
_m_packssdw _mm_sub_pi16 _m_psraw _m_pcmpeqw
_mm_packs_pu16 _m_psubw _mm_srai_pi16 _mm_cmpgt_pi16
_m_packuswb _mm_sub_pi32 _m_psrawi _m_pcmpgtw
_mm_unpackhi_pi8 _m_psubd _mm_sra_pi32 _mm_cmpeq_pi32
_m_punpckhbw _mm_sub_si64 _m_psrad _m_pcmpeqd
_mm_unpackhi_pi16 _mm_subs_pi8 _mm_srai_pi32 _mm_cmpgt_pi32
_m_punpckhwd _m_psubsb _m_psradi _m_pcmpgtd
_mm_unpackhi_pi32 _mm_subs_pi16 _mm_srl_pi16 _mm_setzero_si64
_m_punpckhdq _m_psubsw _m_psrlw _mm_set_pi32
_mm_unpacklo_pi8 _mm_subs_pu8 _mm_srli_pi16 _mm_set_pi16
_m_punpcklbw _m_psubusb _m_psrlwi _mm_set_pi8
_mm_unpacklo_pi16 _mm_subs_pu16 _mm_srl_pi32 _mm_setr_pi32
_m_punpcklwd _m_psubusw _m_psrld _mm_setr_pi16
_mm_unpacklo_pi32 _mm_madd_pi16 _mm_srli_pi32 _mm_setr_pi8
_m_punpckldq _m_pmaddwd _m_psrldi _mm_set1_pi32
_mm_add_pi8 _mm_mulhi_pi16 _mm_srl_si64 _mm_set1_pi16PGI® User’s Guide
306
_m_paddb _m_pmulhw _m_psrlq _mm_set1_pi8
_mm_add_pi16 _mm_mullo_pi16 _mm_srli_si64
_m_paddw _m_pmullw _m_psrlqi
_mm_add_pi32 _mm_sll_pi16 _mm_and_si64
SSE Intrinsics
PGI supports a set of SSE Intrinsics which allow the use of the SSE instructions directly from C/C++ code,
without writing the assembly instructions. The following tables list the SSE intrinsics that PGI supports.
Note
Intrinsics with a * are only available on 64-bit systems.
Table 20.2. SSE Intrinsics (xmmintrin.h)
_mm_add_ss _mm_comige_ss _mm_load_ss
_mm_sub_ss _mm_comineq_ss _mm_load1_ps
_mm_mul_ss _mm_ucomieq_ss _mm_load_ps1
_mm_div_ss _mm_ucomilt_ss _mm_load_ps
_mm_sqrt_ss _mm_ucomile_ss _mm_loadu_ps
_mm_rcp_ss _mm_ucomigt_ss _mm_loadr_ps
_mm_rsqrt_ss _mm_ucomige_ss _mm_set_ss
_mm_min_ss _mm_ucomineq_ss _mm_set1_ps
_mm_max_ss _mm_cvtss_si32 _mm_set_ps1
_mm_add_ps _mm_cvt_ss2si _mm_set_ps
_mm_sub_ps _mm_cvtss_si64x* _mm_setr_ps
_mm_mul_ps _mm_cvtps_pi32 _mm_store_ss
_mm_div_ps _mm_cvt_ps2pi _mm_store_ps
_mm_sqrt_ps _mm_cvttss_si32 _mm_store1_ps
_mm_rcp_ps _mm_cvtt_ss2si _mm_store_ps1
_mm_rsqrt_ps _mm_cvttss_si64x* _mm_storeu_ps
_mm_min_ps _mm_cvttps_pi32 _mm_storer_ps
_mm_max_ps _mm_cvtt_ps2pi _mm_move_ss
_mm_and_ps _mm_cvtsi32_ss _mm_extract_pi16
_mm_andnot_ps _mm_cvt_si2ss _m_pextrw
_mm_or_ps _mm_cvtsi64x_ss* _mm_insert_pi16
_mm_xor_ps _mm_cvtpi32_ps _m_pinsrw
_mm_cmpeq_ss _mm_cvt_pi2ps _mm_max_pi16
_mm_cmplt_ss _mm_movelh_ps _m_pmaxswChapter 20. C/C++ MMX/SSE Inline Intrinsics
307
_mm_cmple_ss _mm_setzero_ps _mm_max_pu8
_mm_cmpgt_ss _mm_cvtpi16_ps _m_pmaxub
_mm_cmpge_ss _mm_cvtpu16_ps _mm_min_pi16
_mm_cmpneq_ss _mm_cvtpi8_ps _m_pminsw
_mm_cmpnlt_ss _mm_cvtpu8_ps _mm_min_pu8
_mm_cmpnle_ss _mm_cvtpi32x2_ps _m_pminub
_mm_cmpngt_ss _mm_movehl_ps _mm_movemask_pi8
_mm_cmpnge_ss _mm_cvtps_pi16 _m_pmovmskb
_mm_cmpord_ss _mm_cvtps_pi8 _mm_mulhi_pu16
_mm_cmpunord_ss _mm_shuffle_ps _m_pmulhuw
_mm_cmpeq_ps _mm_unpackhi_ps _mm_shuffle_pi16
_mm_cmplt_ps _mm_unpacklo_ps _m_pshufw
_mm_cmple_ps _mm_loadh_pi _mm_maskmove_si64
_mm_cmpgt_ps _mm_storeh_pi _m_maskmovq
_mm_cmpge_ps _mm_loadl_pi _mm_avg_pu8
_mm_cmpneq_ps _mm_storel_pi _m_pavgb
_mm_cmpnlt_ps _mm_movemask_ps _mm_avg_pu16
_mm_cmpnle_ps _mm_getcsr _m_pavgw
_mm_cmpngt_ps _MM_GET_EXCEPTION_STATE _mm_sad_pu8
_mm_cmpnge_ps _MM_GET_EXCEPTION_MASK _m_psadbw
_mm_cmpord_ps _MM_GET_ROUNDING_MODE _mm_prefetch
_mm_cmpunord_ps _MM_GET_FLUSH_ZERO_MODE _mm_stream_pi
_mm_comieq_ss _mm_setcsr _mm_stream_ps
_mm_comilt_ss _MM_SET_EXCEPTION_STATE _mm_sfence
_mm_comile_ss _MM_SET_EXCEPTION_MASK _mm_pause
_mm_comigt_ss _MM_SET_ROUNDING_MODE _MM_TRANSPOSE4_PS
_MM_SET_FLUSH_ZERO_MODE
Table 20.3. SSE2 Intrinsics (emmintrin.h)
_mm_load_sd _mm_cmpge_sd _mm_cvtps_pd _mm_srl_epi32
_mm_load1_pd _mm_cmpneq_sd _mm_cvtsd_si32 _mm_srl_epi64
_mm_load_pd1 _mm_cmpnlt_sd _mm_cvtsd_si64x* _mm_slli_epi16
_mm_load_pd _mm_cmpnle_sd _mm_cvttsd_si32 _mm_slli_epi32
_mm_loadu_pd _mm_cmpngt_sd _mm_cvttsd_si64x* _mm_slli_epi64
_mm_loadr_pd _mm_cmpnge_sd _mm_cvtsd_ss _mm_srai_epi16
_mm_set_sd _mm_cmpord_sd _mm_cvtsi32_sd _mm_srai_epi32PGI® User’s Guide
308
_mm_set1_pd _mm_cmpunord_sd _mm_cvtsi64x_sd* _mm_srli_epi16
_mm_set_pd1 _mm_comieq_sd _mm_cvtss_sd _mm_srli_epi32
_mm_set_pd _mm_comilt_sd _mm_unpackhi_pd _mm_srli_epi64
_mm_setr_pd _mm_comile_sd _mm_unpacklo_pd _mm_and_si128
_mm_setzero_pd _mm_comigt_sd _mm_loadh_pd _mm_andnot_si128
_mm_store_sd _mm_comige_sd _mm_storeh_pd _mm_or_si128
_mm_store_pd _mm_comineq_sd _mm_loadl_pd _mm_xor_si128
_mm_store1_pd _mm_ucomieq_sd _mm_storel_pd _mm_cmpeq_epi8
_mm_store_pd1 _mm_ucomilt_sd _mm_movemask_pd _mm_cmpeq_epi16
_mm_storeu_pd _mm_ucomile_sd _mm_packs_epi16 _mm_cmpeq_epi32
_mm_storer_pd _mm_ucomigt_sd _mm_packs_epi32 _mm_cmplt_epi8
_mm_move_sd _mm_ucomige_sd _mm_packus_epi16 _mm_cmplt_epi16
_mm_add_pd _mm_ucomineq_sd _mm_unpackhi_epi8 _mm_cmplt_epi32
_mm_add_sd _mm_load_si128 _mm_unpackhi_epi16 _mm_cmpgt_epi8
_mm_sub_pd _mm_loadu_si128 _mm_unpackhi_epi32 _mm_cmpgt_epi16
_mm_sub_sd _mm_loadl_epi64 _mm_unpackhi_epi64 _mm_srl_epi16
_mm_mul_pd _mm_store_si128 _mm_unpacklo_epi8 _mm_cmpgt_epi32
_mm_mul_sd _mm_storeu_si128 _mm_unpacklo_epi16 _mm_max_epi16
_mm_div_pd _mm_storel_epi64 _mm_unpacklo_epi32 _mm_max_epu8
_mm_div_sd _mm_movepi64_pi64 _mm_unpacklo_epi64 _mm_min_epi16
_mm_sqrt_pd _mm_move_epi64 _mm_add_epi8 _mm_min_epu8
_mm_sqrt_sd _mm_setzero_si128 _mm_add_epi16 _mm_movemask_epi8
_mm_min_pd _mm_set_epi64 _mm_add_epi32 _mm_mulhi_epu16
_mm_min_sd _mm_set_epi32 _mm_add_epi64 _mm_maskmoveu_si128
_mm_max_pd _mm_set_epi64x* _mm_adds_epi8 _mm_avg_epu8
_mm_max_sd _mm_set_epi16 _mm_adds_epi16 _mm_avg_epu16
_mm_and_pd _mm_set_epi8 _mm_adds_epu8 _mm_sad_epu8
_mm_andnot_pd _mm_set1_epi64 _mm_adds_epu16 _mm_stream_si32
_mm_or_pd _mm_set1_epi32 _mm_sub_epi8 _mm_stream_si128
_mm_xor_pd _mm_set1_epi64x* _mm_sub_epi16 _mm_stream_pd
_mm_cmpeq_pd _mm_set1_epi16 _mm_sub_epi32 _mm_movpi64_epi64
_mm_cmplt_pd _mm_set1_epi8 _mm_sub_epi64 _mm_lfence
_mm_cmple_pd _mm_setr_epi64 _mm_subs_epi8 _mm_mfence
_mm_cmpgt_pd _mm_setr_epi32 _mm_subs_epi16 _mm_cvtsi32_si128
_mm_cmpge_pd _mm_setr_epi16 _mm_subs_epu8 _mm_cvtsi64x_si128*
_mm_cmpneq_pd _mm_setr_epi8 _mm_subs_epu16 _mm_cvtsi128_si32Chapter 20. C/C++ MMX/SSE Inline Intrinsics
309
_mm_cmpnlt_pd _mm_cvtepi32_pd _mm_madd_epi16 _mm_cvtsi128_si64x*
_mm_cmpnle_pd _mm_cvtepi32_ps _mm_mulhi_epi16 _mm_srli_si128
_mm_cmpngt_pd _mm_cvtpd_epi32 _mm_mullo_epi16 _mm_slli_si128
_mm_cmpnge_pd _mm_cvtpd_pi32 _mm_mul_su32 _mm_shuffle_pd
_mm_cmpord_pd _mm_cvtpd_ps _mm_mul_epu32 _mm_shufflehi_epi16
_mm_cmpunord_pd _mm_cvttpd_epi32 _mm_sll_epi16 _mm_shufflelo_epi16
_mm_cmpeq_sd _mm_cvttpd_pi32 _mm_sll_epi32 _mm_shuffle_epi32
_mm_cmplt_sd _mm_cvtpi32_pd _mm_sll_epi64 _mm_extract_epi16
_mm_cmple_sd _mm_cvtps_epi32 _mm_sra_epi16 _mm_insert_epi16
_mm_cmpgt_sd _mm_cvttps_epi32 _mm_sra_epi32
Table 20.4. SSE3 Intrinsics (pmmintrin.h)
_mm_addsub_ps _mm_moveldup_ps _mm_loaddup_pd _mm_mwait
_mm_hadd_ps _mm_addsub_pd _mm_movedup_pd
_mm_hsub_ps _mm_hadd_pd _mm_lddqu_si128
_mm_movehdup_ps _mm_hsub_pd _mm_monitor
Table 20.5. SSSE3 Intrinsics (tmmintrin.h)
_mm_hadd_epi16 _mm_hsubs_pi16 _mm_sign_pi16
_mm_hadd_epi32 _mm_maddubs_epi16 _mm_sign_pi32
_mm_hadds_epi16 _mm_maddubs_pi16 _mm_alignr_epi8
_mm_hadd_pi16 _mm_mulhrs_epi16 _mm_alignr_pi8
_mm_hadd_pi32 _mm_mulhrs_pi16 _mm_abs_epi8
_mm_hadds_pi16 _mm_shuffle_epi8 _mm_abs_epi16
_mm_hsub_epi16 _mm_shuffle_pi8 _mm_abs_epi32
_mm_hsub_epi32 _mm_sign_epi8 _mm_abs_pi8
_mm_hsubs_epi16 _mm_sign_epi16 _mm_abs_pi16
_mm_hsub_pi16 _mm_sign_epi32 _mm_abs_pi32
_mm_hsub_pi32 _mm_sign_pi8
Table 20.6. SSE4a Intrinsics (ammintrin.h)
_mm_stream_sd _mm_extract_si64 _mm_insert_si64
_mm_stream_ss _mm_extracti_si64 _mm_inserti_si64
ABM Intrinsics
PGI supports a set of ABM Intrinsics which allow the use of the ABM instructions directly from C/C++ code,
without writing the assembly instructions. The following table lists the ABM intrinsics that PGI supports.PGI® User’s Guide
310
Table 20.7. SSE4a Intrinsics (intrin.h)
__lzcnt16 __lzcnt64 __popcnt __rdtscp
__lzcnt __popcnt16 __popcnt64311
Chapter 21. Fortran Module/Library
Interfaces
PGI Visual Fortran provides access to a number of libraries that export C interfaces by using Fortran modules.
PGI uses this mechanism to support the Win32 API and Unix/Linux portability libraries. This chapter describes
the Fortran module library interfaces that PGIsupports, describing each property available.
Data Types
Because the Win32 API and Portability interfaces resolve to C language libraries, it is important to understand
how the data types compare within the two languages. Here is a table summarizing how C types correspond
with Fortran types for some of the more common data types:
Table 21.1. Fortran Data Type Mappings
C Win32 Data Type Fortran Data Type
BOOL LOGICAL(4)
BYTE BYTE
CHAR CHARACTER
SHORT, WORD INTEGER(2)
DWORD, INT, LONG INTEGER(4)
LONG LONG INTEGER(8)
FLOAT REAL(4)
DOUBLE REAL(8)
x86 Pointers INTEGER(4)
x64 Pointers INTEGER(8)
For more information on data types, refer to “Fortran Data Types,” on page 151.PGI® User’s Guide
312
Using DFLIB and DFPORT
PGI also includes Fortran module interfaces to libraries supporting some standard C library and Unix/Linux
system call functionality. These functions are provided by the DFLIB and DFPORT modules. To utilize these
modules, add the appropriate USE statement:
USE DFLIB
USE DFPORT
DFLIB
The following table lists the functions that DFLIB includes:
commitqq gettim setenvqq
getdrivedirqq renamefileqq signalqq
getenvqq runqq systemqq
DFPORT
The following table lists the functions that DFPORT includes:
abort access alarm besj0 besj1 besjn
besy0 besy1 besyn chdir chmod ctime
date dbesj0 dbesj1 dbesjn dbesy0 dbesy1
dbesyn dffrac dflmax dflmin drandm dsecnds
dtime etime exit fdate ffrac fgetc
flmax flmin flush fork fputc free
fseek fseek64 fstat ftell ftell64 gerror
getarg getc getcwd getenv getfd getgid
getlog getpid getuid gmtime hostnm iargc
idate ierrno inmax ioinit irand1 irand2
irandm isatty itime kill link lnblnk
loc long lstat ltime malloc mclock
outstr perror putc putenv qsort rand1
rand2 random rename rindex rtc secnds
short signal sleep srand1 srand2 stat
stime symlnk system time timef times
ttynam unlink wait
Using the DFWIN module
The DFWIN module includes all the modules needed to access the Win32 API. You can use modules
supporting specific portions of the Win32 API separately. DFWIN is the only module you need to access the
Fortran interfaces to the Win32 API. Simply add the USE DFWIN line to your Fortran code to use this module.Chapter 21. Fortran Module/Library Interfaces
313
To utilize any of the Win32 API interfaces, add a Fortran USE statement for the library or module that includes
it. For example, to use user32.lib, add the following Fortran USE statement:
USE DFWIN
For a mapping of module names to the corresponding Win32 API library and header files, refer to The
Microsoft Windows API documentation.. The function calls made through the module interfaces ultimately
resolve to C Language interfaces, so some accommodation for inter-language calling conventions must be
made in the Fortran application. These accommodations include:
• On x64 platforms, pointers and pointer types such as HANDLE, HINSTANCE, WPARAM, and HWND must
be treated as 8-byte quantities (INTEGER(8)). On x86 (32-bit) platforms, these are 4-byte quantities
((INTEGER(4)).
• In general, C makes calls by value while Fortran makes calls by reference.
• When doing Windows development one must sometimes provide callback functions for message processing,
dialog processing, etc. These routines are called by the Windows system when events are processed. In
order to provide the expected function signature for a callback function, the user may need to use the
STDCALL attribute directive (!DEC$ATTRIBUTE::STDCALL) in the declaration. See the PVF examples for
more detail on how to implement callbacks.
Supported Libraries and Modules
The following tables provide lists of the functions in each library or module that PGI supports in DFWIN.
advapi32
The following table lists the functions that advapi32 includes:
AccessCheckAndAuditAlarm AccessCheckByType
AccessCheckByTypeAndAuditAlarm AccessCheckByTypeResultList
AccessCheckByTypeResultListAndAuditAlarm AccessCheckByTypeResultListAndAuditAlarmByHandle
AddAccessAllowedAce AddAccessAllowedAceEx
AddAccessAllowedObjectAce AddAccessDeniedAce
AddAccessDeniedAceEx AddAccessDeniedObjectAce
AddAce AddAuditAccessAce
AddAuditAccessAceEx AddAuditAccessObjectAce
AdjustTokenGroups AdjustTokenPrivileges
AllocateAndInitializeSid AllocateLocallyUniqueId
AreAllAccessesGranted AreAnyAccessesGranted
BackupEventLog CheckTokenMembership
ClearEventLog CloseEncryptedFileRaw
CloseEventLog ConvertToAutoInheritPrivateObjectSecurity
CopySid CreatePrivateObjectSecurity
CreatePrivateObjectSecurityEx CreatePrivateObjectSecurityWithMultipleInheritancePGI® User’s Guide
314
CreateProcessAsUser CreateProcessWithLogonW
CreateProcessWithTokenW CreateRestrictedToken
CreateWellKnownSid DecryptFile
DeleteAce DeregisterEventSource
DestroyPrivateObjectSecurity DuplicateToken
DuplicateTokenEx EncryptFile
EqualDomainSid EqualPrefixSid
EqualSid FileEncryptionStatus
FindFirstFreeAce FreeSid
GetAce GetAclInformation
GetCurrentHwProfile GetEventLogInformation
GetFileSecurity GetKernelObjectSecurity
GetLengthSid GetNumberOfEventLogRecords
GetOldestEventLogRecord GetPrivateObjectSecurity
GetSecurityDescriptorControl GetSecurityDescriptorDacl
GetSecurityDescriptorGroup GetSecurityDescriptorLength
GetSecurityDescriptorOwner GetSecurityDescriptorRMControl
GetSecurityDescriptorSacl GetSidIdentifierAuthority
GetSidLengthRequired GetSidSubAuthority
GetSidSubAuthorityCount GetTokenInformation
GetUserName GetWindowsAccountDomainSid
ImpersonateAnonymousToken ImpersonateLoggedOnUser
ImpersonateNamedPipeClient ImpersonateSelf
InitializeAcl InitializeSecurityDescriptor
InitializeSid IsTextUnicode
IsTokenRestricted IsTokenUntrusted
IsValidAcl IsValidSecurityDescriptor
IsValidSid IsWellKnownSid
LogonUser LogonUserEx
LookupAccountName LookupAccountSid
LookupPrivilegeDisplayName LookupPrivilegeName
LookupPrivilegeValue MakeAbsoluteSD
MakeAbsoluteSD2 MakeSelfRelativeSD
MapGenericMask NotifyChangeEventLog
ObjectCloseAuditAlarm ObjectDeleteAuditAlarm
ObjectOpenAuditAlarm ObjectPrivilegeAuditAlarmChapter 21. Fortran Module/Library Interfaces
315
OpenBackupEventLog OpenEncryptedFileRaw
OpenEventLog OpenProcessToken
OpenThreadToken PrivilegeCheck
PrivilegedServiceAuditAlarm ReadEncryptedFileRaw
ReadEventLog RegisterEventSource
ReportEvent RevertToSelf
SetAclInformation SetFileSecurity
SetKernelObjectSecurity SetPrivateObjectSecurity
SetPrivateObjectSecurityEx SetSecurityDescriptorControl
SetSecurityDescriptorDacl SetSecurityDescriptorGroup
SetSecurityDescriptorOwner SetSecurityDescriptorRMControl
SetSecurityDescriptorSacl SetThreadToken
SetTokenInformation WriteEncryptedFileRaw
comdlg32
The following table lists the functions that comdlg32 includes:
AfxReplaceText ChooseColor ChooseFont
CommDlgExtendedError FindText GetFileTitle
GetOpenFileName GetSaveFileName PageSetupDlg
PrintDlg PrintDlgEx ReplaceText
dfwbase
These are the functions that dfwbase includes:
chartoint LoByte MakeWord
chartoreal LoWord MakeWparam
CopyMemory LoWord64 PaletteIndex
GetBlueValue MakeIntAtom PaletteRGB
GetGreenValue MakeIntResource PrimaryLangID
GetRedValue MakeLangID RGB
HiByte MakeLCID RtlCopyMemory
HiWord MakeLong SortIDFromLCID
HiWord64 MakeLParam SubLangID
inttochar MakeLResult
dfwinty
These are the functions that dfwinty includes:PGI® User’s Guide
316
dwNumberOfFunctionKeys rdFunction
gdi32
These are the functions that gdi32 includes:
AbortDoc AbortPath AddFontMemResourceEx
AddFontResource AddFontResourceEx AlphaBlend
AngleArc AnimatePalette Arc
ArcTo BeginPath BitBlt
CancelDC CheckColorsInGamut ChoosePixelFormat
Chord CloseEnhMetaFile CloseFigure
CloseMetaFile ColorCorrectPalette ColorMatchToTarget
CombineRgn CombineTransform CopyEnhMetaFile
CopyMetaFile CreateBitmap CreateBitmapIndirect
CreateBrushIndirect CreateColorSpace CreateCompatibleBitmap
CreateCompatibleDC CreateDC CreateDIBitmap
CreateDIBPatternBrush CreateDIBPatternBrushPt CreateDIBSection
CreateDiscardableBitmap CreateEllipticRgn CreateEllipticRgnIndirect
CreateEnhMetaFile CreateFont CreateFontIndirect
CreateFontIndirectEx CreateHalftonePalette CreateHatchBrush
CreateIC CreateMetaFile CreatePalette
CreatePatternBrush CreatePen CreatePenIndirect
CreatePolygonRgn CreatePolyPolygonRgn CreateRectRgn
CreateRectRgnIndirect CreateRoundRectRgn CreateScalableFontResource
CreateSolidBrush DeleteColorSpace DeleteDC
DeleteEnhMetaFile DeleteMetaFile DeleteObject
DescribePixelFormat DeviceCapabilities DPtoLP
DrawEscape Ellipse EndDoc
EndPage EndPath EnumEnhMetaFile
EnumFontFamilies EnumFontFamiliesEx EnumFonts
EnumICMProfiles EnumMetaFile EnumObjects
EqualRgn Escape ExcludeClipRect
ExtCreatePen ExtCreateRegion ExtEscape
ExtFloodFill ExtSelectClipRgn ExtTextOut
FillPath FillRgn FixBrushOrgEx
FlattenPath FloodFill FrameRgn
GdiComment GdiFlush GdiGetBatchLimitChapter 21. Fortran Module/Library Interfaces
317
GdiSetBatchLimit GetArcDirection GetAspectRatioFilterEx
GetBitmapBits GetBitmapDimensionEx GetBkColor
GetBkMode GetBoundsRect GetBrushOrgEx
GetCharABCWidthsA GetCharABCWidthsFloat GetCharABCWidthsI
GetCharABCWidthsW GetCharacterPlacement GetCharWidth
GetCharWidth32 GetCharWidthFloat GetCharWidthI
GetClipBox GetClipRgn GetColorAdjustment
GetColorSpace GetCurrentObject GetCurrentPositionEx
GetDCBrushColor GetDCOrgEx GetDCPenColor
GetDeviceCaps GetDeviceGammaRamp GetDIBColorTable
GetDIBits GetEnhMetaFile GetEnhMetaFileBits
GetEnhMetaFileDescriptionA GetEnhMetaFileDescriptionW GetEnhMetaFileHeader
GetEnhMetaFilePaletteEntries GetEnhMetaFilePixelFormat GetFontData
GetFontLanguageInfo GetFontUnicodeRanges GetGlyphIndices
GetGlyphOutline GetGraphicsMode GetICMProfileA
GetICMProfileW GetKerningPairs GetLayout
GetLogColorSpace GetMapMode GetMetaFile
GetMetaFileBitsEx GetMetaRgn GetMiterLimit
GetNearestColor GetNearestPaletteIndex GetObject
GetObjectType GetOutlineTextMetrics GetPaletteEntries
GetPath GetPixel GetPixelFormat
GetPolyFillMode GetRandomRgn GetRasterizerCaps
GetRegionData GetRgnBox GetROP2
GetStockObject GetStretchBltMode GetSystemPaletteEntries
GetSystemPaletteUse GetTextAlign GetTextCharacterExtra
GetTextCharset GetTextCharsetInfo GetTextColor
GetTextExtentExPoint GetTextExtentExPointI GetTextExtentPoint
GetTextExtentPoint32 GetTextExtentPointI GetTextFace
GetTextMetrics GetViewportExtEx GetViewportOrgEx
GetWindowExtEx GetWindowOrgEx GetWinMetaFileBits
GetWorldTransform GradientFill IntersectClipRect
InvertRgn LineDD LineTo
LPtoDP MaskBlt ModifyWorldTransform
MoveToEx OffsetClipRgn OffsetRgn
OffsetViewportOrgEx OffsetWindowOrgEx PaintRgn
PatBlt PathToRegion PiePGI® User’s Guide
318
PlayEnhMetaFile PlayEnhMetaFileRecord PlayMetaFile
PlayMetaFileRecord PlgBlt PolyBezier
PolyBezierTo PolyDraw Polygon
Polyline PolylineTo PolyPolygon
PolyPolyline PolyTextOut PtInRegion
PtVisible RealizePalette Rectangle
RectInRegion RectVisible RemoveFontMemResourceEx
RemoveFontResource RemoveFontResourceEx ResetDC
ResizePalette RestoreDC RoundRect
SaveDC ScaleViewportExtEx ScaleWindowExtEx
SelectClipPath SelectClipRgn SelectObject
SelectPalette SetAbortProc SetArcDirection
SetBitmapBits SetBitmapDimensionEx SetBkColor
SetBkMode SetBoundsRect SetBrushOrgEx
SetColorAdjustment SetColorSpace SetDCBrushColor
SetDCPenColor SetDeviceGammaRamp SetDIBColorTable
SetDIBits SetDIBitsToDevice SetEnhMetaFileBits
SetGraphicsMode SetICMMode SetICMProfile
SetLayout SetMapMode SetMapperFlags
SetMetaFileBitsEx SetMetaRgn SetMiterLimit
SetPaletteEntries SetPixel SetPixelFormat
SetPixelV SetPolyFillMode SetRectRgn
SetROP2 SetStretchBltMode SetSystemPaletteUse
SetTextAlign SetTextCharacterExtra SetTextColor
SetTextJustification SetViewportExtEx SetViewportOrgEx
SetWindowExtEx SetWindowOrgEx SetWinMetaFileBits
SetWorldTransform StartDoc StartPage
StretchBlt StretchDIBits StrokeAndFillPath
StrokePath SwapBuffers TextOut
TranslateCharsetInfo TransparentBlt UnrealizeObject
UpdateColors UpdateICMRegKey wglCopyContext
wglCreateContext wglCreateLayerContext wglDeleteContext
wglDescribeLayerPlane wglGetCurrentContext wglGetCurrentDC
wglGetLayerPaletteEntries wglGetProcAddress wglMakeCurrent
wglRealizeLayerPalette wglSetLayerPaletteEntries wglShareLists
wglSwapLayerBuffers wglSwapMultipleBuffers wglUseFontBitmapsChapter 21. Fortran Module/Library Interfaces
319
wglUseFontOutlines WidenPath
kernel32
These are the functions that kernel32 includes:
ActivateActCtx AddAtom
AddConsoleAlias AddRefActCtx
AddVectoredContinueHandler AddVectoredExceptionHandler
AllocateUserPhysicalPages AllocConsole
AreFileApisANSI AssignProcessToJobObject
AttachConsole BackupRead
BackupSeek BackupWrite
Beep BeginUpdateResource
BindIoCompletionCallback BuildCommDCB
BuildCommDCBAndTimeouts CallNamedPipe
CancelDeviceWakeupRequest CancelIo
CancelTimerQueueTimer CancelWaitableTimer
CheckNameLegalDOS8Dot3 CheckRemoteDebuggerPresent
ClearCommBreak ClearCommError
CloseHandle CommConfigDialog
CompareFileTime ConnectNamedPipe
ContinueDebugEvent ConvertFiberToThread
ConvertThreadToFiber ConvertThreadToFiberEx
CopyFile CopyFileEx
CreateActCtx CreateConsoleScreenBuffer
CreateDirectory CreateDirectoryEx
CreateEvent CreateFiber
CreateFiberEx CreateFile
CreateFileMapping CreateHardLink
CreateIoCompletionPort CreateJobObject
CreateJobSet CreateMailslot
CreateMemoryResourceNotification CreateMutex
CreateNamedPipe CreatePipe
CreateProcess CreateRemoteThread
CreateSemaphore CreateTapePartition
CreateThread CreateTimerQueue
CreateTimerQueueTimer CreateWaitableTimerPGI® User’s Guide
320
DeactivateActCtx DebugActiveProcess
DebugActiveProcessStop DebugBreak
DebugBreakProcess DebugSetProcessKillOnExit
DecodePointer DecodeSystemPointer
DefineDosDevice DeleteAtom
DeleteCriticalSection DeleteFiber
DeleteFile DeleteTimerQueue
DeleteTimerQueueEx DeleteTimerQueueTimer
DeleteVolumeMountPoint DeviceIoControl
DisableThreadLibraryCalls DisconnectNamedPipe
DnsHostnameToComputerName DosDateTimeToFileTime
DuplicateHandle EncodePointer
EncodeSystemPointer EndUpdateResource
EnterCriticalSection EnumResourceLanguages
EnumResourceNames EnumResourceTypes
EnumSystemFirmwareTables EraseTape
EscapeCommFunction ExitProcess
ExitThread ExpandEnvironmentStrings
FatalAppExit FatalExit
FileTimeToDosDateTime FileTimeToLocalFileTime
FileTimeToSystemTime FillConsoleOutputAttribute
FillConsoleOutputCharacter FindActCtxSectionGuid
FindActCtxSectionString FindAtom
FindClose FindCloseChangeNotification
FindFirstChangeNotification FindFirstFile
FindFirstFileEx FindFirstVolume
FindFirstVolumeMountPoint FindNextChangeNotification
FindNextFile FindNextVolume
FindNextVolumeMountPoint FindResource
FindResourceEx FindVolumeClose
FindVolumeMountPointClose FlsAlloc
FlsFree FlsGetValue
FlsSetValue FlushConsoleInputBuffer
FlushFileBuffers FlushInstructionCache
FlushViewOfFile FormatMessage
FreeConsole FreeEnvironmentStringsChapter 21. Fortran Module/Library Interfaces
321
FreeLibrary FreeLibraryAndExitThread
FreeResource FreeUserPhysicalPages
GenerateConsoleCtrlEvent GetAtomName
GetBinaryType GetCommandLine
GetCommConfig GetCommMask
GetCommModemStatus GetCommProperties
GetCommState GetCommTimeouts
GetCompressedFileSize GetComputerName
GetConsoleAlias GetConsoleAliases
GetConsoleAliasesLength GetConsoleAliasExes
GetConsoleAliasExesLength GetConsoleCP
GetConsoleCursorInfo GetConsoleDisplayMode
GetConsoleFontSize GetConsoleMode
GetConsoleOutputCP GetConsoleProcessList
GetConsoleScreenBufferInfo GetConsoleSelectionInfo
GetConsoleTitle GetConsoleWindow
GetCurrentActCtx GetCurrentConsoleFont
GetCurrentDirectory GetCurrentProcess
GetCurrentProcessId GetCurrentProcessorNumber
GetCurrentThread GetCurrentThreadId
GetDefaultCommConfig GetDevicePowerState
GetDiskFreeSpace GetDiskFreeSpaceEx
GetDllDirectory GetDriveType
GetEnvironmentStrings GetEnvironmentVariable
GetExitCodeProcess GetExitCodeThread
GetFileAttributes GetFileAttributesEx
GetFileInformationByHandle GetFileSize
GetFileSizeEx GetFileTime
GetFileType GetFirmwareEnvironmentVariable
GetFullPathName GetHandleInformation
GetLargePageMinimum GetLargestConsoleWindowSize
GetLastError GetLocalTime
GetLogicalDrives GetLogicalDriveStrings
GetLogicalProcessorInformation GetLongPathName
GetMailslotInfo GetModuleFileName
GetModuleHandle GetModuleHandleExPGI® User’s Guide
322
GetNamedPipeHandleState GetNamedPipeInfo
GetNativeSystemInfo GetNumaAvailableMemoryNode
GetNumaHighestNodeNumber GetNumaNodeProcessorMask
GetNumaProcessorNode GetNumberOfConsoleInputEvents
GetNumberOfConsoleMouseButtons GetOverlappedResult
GetPriorityClass GetPrivateProfileInt
GetPrivateProfileSection GetPrivateProfileSectionNames
GetPrivateProfileString GetPrivateProfileStruct
GetProcAddress GetProcessAffinityMask
GetProcessHandleCount GetProcessHeap
GetProcessHeaps GetProcessId
GetProcessIdOfThread GetProcessIoCounters
GetProcessPriorityBoost GetProcessShutdownParameters
GetProcessTimes GetProcessVersion
GetProcessWorkingSetSize GetProcessWorkingSetSizeEx
GetProfileInt GetProfileSection
GetProfileString GetQueuedCompletionStatus
GetShortPathName GetStartupInfo
GetStdHandle GetSystemDirectory
GetSystemFirmwareTable GetSystemInfo
GetSystemRegistryQuota GetSystemTime
GetSystemTimeAdjustment GetSystemTimeAsFileTime
GetSystemWindowsDirectory GetSystemWow64Directory
GetTapeParameters GetTapePosition
GetTapeStatus GetTempFileName
GetTempPath GetThreadContext
GetThreadId GetThreadIOPendingFlag
GetThreadPriority GetThreadPriorityBoost
GetThreadSelectorEntry GetThreadTimes
GetTickCount GetTimeZoneInformation
GetVersion GetVersionEx
GetVolumeInformation GetVolumeNameForVolumeMountPoint
GetVolumePathName GetVolumePathNamesForVolumeName
GetWindowsDirectory GetWriteWatch
GlobalAddAtom GlobalAlloc
GlobalCompact GlobalDeleteAtomChapter 21. Fortran Module/Library Interfaces
323
GlobalFindAtom GlobalFix
GlobalFlags GlobalFree
GlobalGetAtomName GlobalHandle
GlobalLock GlobalMemoryStatus
GlobalMemoryStatusEx GlobalReAlloc
GlobalSize GlobalUnfix
GlobalUnlock GlobalUnWire
GlobalWire HeapAlloc
HeapCompact HeapCreate
HeapDestroy HeapFree
HeapLock HeapQueryInformation
HeapReAlloc HeapSetInformation
HeapSize HeapUnlock
HeapValidate HeapWalk
InitAtomTable InitializeCriticalSection
InitializeCriticalSectionAndSpinCount InitializeSListHead
InterlockedCompareExchange InterlockedCompareExchange64
InterlockedDecrement InterlockedExchange
InterlockedExchangeAdd InterlockedFlushSList
InterlockedIncrement InterlockedPopEntrySList
InterlockedPushEntrySList IsBadCodePtr
IsBadHugeReadPtr IsBadHugeWritePtr
IsBadReadPtr IsBadStringPtr
IsBadWritePtr IsDebuggerPresent
IsProcessInJob IsProcessorFeaturePresent
IsSystemResumeAutomatic LeaveCriticalSection
LoadLibrary LoadLibraryEx
LoadModule LoadResource
LocalAlloc LocalCompact
LocalFileTimeToFileTime LocalFlags
LocalFree LocalHandle
LocalLock LocalReAlloc
LocalShrink LocalSize
LocalUnlock LockFile
LockFileEx LockResource
lstrcat lstrcmpPGI® User’s Guide
324
lstrcmpi lstrcpy
lstrcpyn lstrlen
MapUserPhysicalPages MapUserPhysicalPagesScatter
MapViewOfFile MapViewOfFileEx
MoveFile MoveFileEx
MoveFileWithProgress MulDiv
NeedCurrentDirectoryForExePath OpenEvent
OpenFile OpenFileMapping
OpenJobObject OpenMutex
OpenProcess OpenSemaphore
OpenThread OpenWaitableTimer
OutputDebugString PeekConsoleInput
PeekNamedPipe PostQueuedCompletionStatus
PrepareTape ProcessIdToSessionId
PulseEvent PurgeComm
QueryActCtxW QueryDepthSList
QueryDosDevice QueryInformationJobObject
QueryMemoryResourceNotification QueryPerformanceCounter
QueryPerformanceFrequency QueueUserAPC
QueueUserWorkItem RaiseException
ReadConsole ReadConsoleInput
ReadConsoleOutput ReadConsoleOutputAttribute
ReadConsoleOutputCharacter ReadDirectoryChangesW
ReadFile ReadFileEx
ReadFileScatter ReadProcessMemory
RegisterWaitForSingleObject RegisterWaitForSingleObjectEx
ReleaseActCtx ReleaseMutex
ReleaseSemaphore RemoveDirectory
RemoveVectoredContinueHandler RemoveVectoredExceptionHandler
ReOpenFile ReplaceFile
RequestDeviceWakeup RequestWakeupLatency
ResetEvent ResetWriteWatch
RestoreLastError ResumeThread
ScrollConsoleScreenBuffer SearchPath
SetCommBreak SetCommConfig
SetCommMask SetCommStateChapter 21. Fortran Module/Library Interfaces
325
SetCommTimeouts SetComputerName
SetComputerNameEx SetConsoleActiveScreenBuffer
SetConsoleCP SetConsoleCtrlHandler
SetConsoleCursorInfo SetConsoleCursorPosition
SetConsoleMode SetConsoleOutputCP
SetConsoleScreenBufferSize SetConsoleTextAttribute
SetConsoleTitle SetConsoleWindowInfo
SetCriticalSectionSpinCount SetCurrentDirectory
SetDefaultCommConfig SetDllDirectory
SetEndOfFile SetEnvironmentStrings
SetEnvironmentVariable SetErrorMode
SetEvent SetFileApisToANSI
SetFileApisToOEM SetFileAttributes
SetFilePointer SetFilePointerEx
SetFileShortName SetFileTime
SetFileValidData SetFirmwareEnvironmentVariable
SetHandleCount SetHandleInformation
SetInformationJobObject SetLastError
SetLocalTime SetMailslotInfo
SetMessageWaitingIndicator SetNamedPipeHandleState
SetPriorityClass SetProcessAffinityMask
SetProcessPriorityBoost SetProcessShutdownParameters
SetProcessWorkingSetSize SetProcessWorkingSetSizeEx
SetStdHandle SetSystemTime
SetSystemTimeAdjustment SetTapeParameters
SetTapePosition SetThreadAffinityMask
SetThreadContext SetThreadExecutionState
SetThreadIdealProcessor SetThreadPriority
SetThreadPriorityBoost SetThreadStackGuarantee
SetTimerQueueTimer SetTimeZoneInformation
SetUnhandledExceptionFilter SetupComm
SetVolumeLabel SetVolumeMountPoint
SetWaitableTimer SignalObjectAndWait
SizeofResource Sleep
SleepEx SuspendThread
SwitchToFiber SwitchToThreadPGI® User’s Guide
326
SystemTimeToFileTime SystemTimeToTzSpecificLocalTime
TerminateJobObject TerminateProcess
TerminateThread TlsAlloc
TlsFree TlsGetValue
TlsSetValue TransactNamedPipe
TransmitCommChar TryEnterCriticalSection
TzSpecificLocalTimeToSystemTime UnhandledExceptionFilter
UnlockFile UnlockFileEx
UnmapViewOfFile UnregisterWait
UnregisterWaitEx UpdateResource
VerifyVersionInfo VirtualAlloc
VirtualAllocEx VirtualFree
VirtualFreeEx VirtualLock
VirtualProtect VirtualProtectEx
VirtualQuery VirtualQueryEx
VirtualUnlock WaitCommEvent
WaitForDebugEvent WaitForMultipleObjects
WaitForMultipleObjectsEx WaitForSingleObject
WaitForSingleObjectEx WaitNamedPipe
WinExec Wow64DisableWow64FsRedirection
Wow64EnableWow64FsRedirection Wow64RevertWow64FsRedirection
WriteConsole WriteConsoleInput
WriteConsoleOutput WriteConsoleOutputAttribute
WriteConsoleOutputCharacter WriteFile
WriteFileEx WriteFileGather
WritePrivateProfileSection WritePrivateProfileString
WritePrivateProfileStruct WriteProcessMemory
WriteProfileSection WriteProfileString
WriteTapemark WTSGetActiveConsoleSessionId
ZombifyActCtx _hread
_hwrite _lclose
_lcreat _llseek
_lopen _lread
_lwriteChapter 21. Fortran Module/Library Interfaces
327
shell32
These are the functions that shell32 includes:
DoEnvironmentSubst ShellExecuteEx
DragAcceptFiles Shell_NotifyIcon
DragFinish SHEmptyRecycleBin
DragQueryFile SHFileOperation
DragQueryPoint SHFreeNameMappings
DuplicateIcon SHGetDiskFreeSpaceEx
ExtractAssociatedIcon SHGetFileInfo
ExtractIcon SHGetNewLinkInfo
ExtractIconEx SHInvokePrinterCommand
FindExecutable SHIsFileAvailableOffline
IsLFNDrive SHLoadNonloadedIconOverlayIdentifiers
SHAppBarMessage SHQueryRecycleBin
SHCreateProcessAsUserW SHSetLocalizedName
ShellAbout WinExecError
ShellExecute
user32
These are the functions that user32 includes:
ActivateKeyboardLayout AdjustWindowRect AdjustWindowRectEx
AllowSetForegroundWindow AnimateWindow AnyPopup
AppendMenu ArrangeIconicWindows AttachThreadInput
BeginDeferWindowPos BeginPaint BringWindowToTop
BroadcastSystemMessage BroadcastSystemMessageEx CallMsgFilter
CallNextHookEx CallWindowProc CascadeWindows
ChangeClipboardChain ChangeDisplaySettings ChangeDisplaySettingsEx
ChangeMenu CharLower CharLowerBuff
CharNext CharNextEx CharPrev
CharPrevEx CharToOem CharToOemBuff
CharUpper CharUpperBuff CheckDlgButton
CheckMenuItem CheckMenuRadioItem CheckRadioButton
ChildWindowFromPoint ChildWindowFromPointEx ClientToScreen
ClipCursor CloseClipboard CloseDesktop
CloseWindow CloseWindowStation CopyAcceleratorTablePGI® User’s Guide
328
CopyCursor CopyIcon CopyImage
CopyRect CountClipboardFormats CreateAcceleratorTable
CreateCaret CreateCursor CreateDesktop
CreateDialogIndirectParam CreateDialogParam CreateIcon
CreateIconFromResource CreateIconFromResourceEx CreateIconIndirect
CreateMDIWindow CreateMenu CreatePopupMenu
CreateWindow CreateWindowEx CreateWindowStation
DeferWindowPos DefFrameProc DefMDIChildProc
DefRawInputProc DefWindowProc DeleteMenu
DeregisterShellHookWindow DestroyAcceleratorTable DestroyCaret
DestroyCursor DestroyIcon DestroyMenu
DestroyWindow DialogBoxIndirectParam DialogBoxParam1
DialogBoxParam2 DisableProcessWindowsGhosting DispatchMessage
DlgDirList DlgDirListComboBox DlgDirSelectComboBoxEx
DlgDirSelectEx DragDetect DragObject
DrawAnimatedRects DrawCaption DrawEdge
DrawFocusRect DrawFrameControl DrawIcon
DrawIconIndirect DrawMenuBar DrawState
DrawText DrawTextEx EmptyClipboard
EnableMenuItem EnableScrollBar EnableWindow
EndDeferWindowPos EndDialog EndMenu
EndPaint EndTask EnumChildWindows
EnumClipboardFormats EnumDesktops EnumDesktopWindows
EnumDisplayDevices EnumDisplayMonitors EnumDisplaySettings
EnumDisplaySettingsEx EnumProps EnumPropsEx
EnumThreadWindows EnumWindows EnumWindowStations
EqualRect ExcludeUpdateRgn ExitWindowsEx
FillRect FindWindow FindWindowEx
FlashWindow FlashWindowEx FrameRect
GetActiveWindow GetAltTabInfo GetAncestor
GetAsyncKeyState GetCapture GetCaretBlinkTime
GetCaretPos GetClassInfo GetClassInfoEx
GetClassLong GetClassLongPtr GetClassName
GetClassWord GetClientRect GetClipboardData
GetClipboardFormatName GetClipboardOwner GetClipboardSequenceNumber
GetClipboardViewer GetClipCursor GetComboBoxInfoChapter 21. Fortran Module/Library Interfaces
329
GetCursor GetCursorInfo GetCursorPos
GetDC GetDCEx GetDesktopWindow
GetDialogBaseUnits GetDlgCtrlID GetDlgItem
GetDlgItemInt GetDlgItemText GetDoubleClickTime
GetFocus GetForegroundWindow GetGuiResources
GetGUIThreadInfo GetIconInfo GetInputState
GetKBCodePage GetKeyboardLayout GetKeyboardLayoutList
GetKeyboardLayoutName GetKeyboardState GetKeyboardType
GetKeyNameText GetKeyState GetLastActivePopup
GetLastInputInfo GetLayeredWindowAttributes GetListBoxInfo
GetMenu GetMenuBarInfo GetMenuCheckMarkDimensions
GetMenuContextHelpId GetMenuDefaultItem GetMenuInfo
GetMenuItemCount GetMenuItemID GetMenuItemInfo
GetMenuItemRect GetMenuState GetMenuString
GetMessage GetMessageExtraInfo GetMessagePos
GetMessageTime GetMonitorInfo GetMouseMovePointsEx
GetNextDlgGroupItem GetNextDlgTabItem GetOpenClipboardWindow
GetParent GetPriorityClipboardFormat GetProcessDefaultLayout
GetProcessWindowStation GetProp GetQueueStatus
GetRawInputBuffer GetRawInputData GetRawInputDeviceInfo
GetRawInputDeviceList GetRegisteredRawInputDevices GetScrollBarInfo
GetScrollInfo GetScrollPos GetScrollRange
GetShellWindow GetSubMenu GetSysColor
GetSysColorBrush GetSystemMenu GetSystemMetrics
GetTabbedTextExtent GetThreadDesktop GetTitleBarInfo
GetTopWindow GetUpdateRect GetUpdateRgn
GetUserObjectInformation GetUserObjectSecurity GetWindow
GetWindowContextHelpId GetWindowDC GetWindowInfo
GetWindowLong GetWindowLongPtr GetWindowModuleFileName
GetWindowPlacement GetWindowRect GetWindowRgn
GetWindowRgnBox GetWindowText GetWindowTextLength
GetWindowThreadProcessId GetWindowWord GrayString
HideCaret HiliteMenuItem InflateRect
InSendMessage InSendMessageEx InsertMenu
InsertMenuItem InternalGetWindowText IntersectRect
InvalidateRect InvalidateRgn InvertRectPGI® User’s Guide
330
IsCharAlpha IsCharAlphaNumeric IsCharLower
IsCharUpper IsChild IsClipboardFormatAvailable
IsDialogMessage IsDlgButtonChecked IsGUIThread
IsHungAppWindow IsIconic IsMenu
IsRectEmpty IsWindow IsWindowEnabled
IsWindowUnicode IsWindowVisible IsWinEventHookInstalled
IsWow64Message IsZoomed keybd_event
KillTimer LoadAccelerators LoadBitmap
LoadCursor1 LoadCursor2 LoadCursorFromFile
LoadIcon1 LoadIcon2 LoadImage
LoadKeyboardLayout LoadMenu1 LoadMenu2
LoadMenuIndirect LoadString LockSetForegroundWindow
LockWindowUpdate LockWorkStation LookupIconIdFromDirectory
LookupIconIdFromDirectoryEx LRESULT MapDialogRect
MapVirtualKey MapVirtualKeyEx MapWindowPoints
MenuItemFromPoint MessageBeep MessageBox
MessageBoxEx MessageBoxIndirect ModifyMenu1
ModifyMenu2 MonitorFromPoint MonitorFromRect
MonitorFromWindow mouse_event MoveWindow
MsgWaitForMultipleObjects MsgWaitForMultipleObjectsEx NotifyWinEvent
OemKeyScan OemToChar OemToCharBuff
OffsetRect OpenClipboard OpenDesktop
OpenIcon OpenInputDesktop OpenWindowStation
PaintDesktop PeekMessage PostMessage
PostQuitMessage PostThreadMessage PrintWindow
PrivateExtractIcons PtInRect RealChildWindowFromPoint
RealGetWindowClass RedrawWindow RegisterClass
RegisterClassEx RegisterClipboardFormat RegisterDeviceNotification
RegisterHotKey RegisterRawInputDevices RegisterShellHookWindow
RegisterWindowMessage ReleaseCapture ReleaseDC
RemoveMenu RemoveProp ReplyMessage
ScreenToClient ScrollDC ScrollWindow
ScrollWindowEx SendDlgItemMessage SendInput
SendMessage SendMessageCallback SendMessageTimeout
SendNotifyMessage SetActiveWindow SetCapture
SetCaretBlinkTime SetCaretPos SetClassLongChapter 21. Fortran Module/Library Interfaces
331
SetClassLongPtr SetClassWord SetClipboardData
SetClipboardViewer SetCursor SetCursorPos
SetDebugErrorLevel SetDlgItemInt SetDlgItemText
SetDoubleClickTime SetFocus SetForegroundWindow
SetKeyboardState SetLastErrorEx SetLayeredWindowAttributes
SetMenu SetMenuContextHelpId SetMenuDefaultItem
SetMenuInfo SetMenuItemBitmaps SetMenuItemInfo
SetMessageExtraInfo SetMessageQueue SetParent
SetProcessDefaultLayout SetProcessWindowStation SetProp
SetRect SetRectEmpty SetScrollInfo
SetScrollPos SetScrollRange SetSysColors
SetSystemCursor SetThreadDesktop SetTimer
SetUserObjectInformation SetUserObjectSecurity SetWindowContextHelpId
SetWindowLong SetWindowLongPtr SetWindowPlacement
SetWindowPos SetWindowRgn SetWindowsHook
SetWindowsHookEx SetWindowText SetWindowWord
SetWinEventHook ShowCaret ShowCursor
ShowOwnedPopups ShowScrollBar ShowWindow
ShowWindowAsync SubtractRect SwapMouseButton
SwitchDesktop SwitchToThisWindow SystemParametersInfo
TabbedTextOut TileWindows ToAscii
ToAsciiEx ToUnicode ToUnicodeEx
TrackMouseEvent TrackPopupMenu TrackPopupMenuEx
TranslateAccelerator TranslateMDISysAccel TranslateMessage
UnhookWindowsHook UnhookWindowsHookEx UnhookWinEvent
UnionRect UnloadKeyboardLayout UnregisterClass
UnregisterDeviceNotification UnregisterHotKey UpdateLayeredWindow
UpdateLayeredWindowIndirect UpdateWindow UserHandleGrantAccess
ValidateRect ValidateRgn VkKeyScan
VkKeyScanEx WaitForInputIdle WaitMessage
WindowFromDC WindowFromPoint WinHelp
wsprintf wvsprintf
winver
These are the functions that winver includes:
GetFileVersionInfo VerInstallFilePGI® User’s Guide
332
GetFileVersionInfoSize VerLanguageName
VerFindFile VerQueryValue
wsock32
These are the functions that wsock32 includes:
accept AcceptEx bind
closesocket connect GetAcceptExSockaddrs
getpeername gethostname getprotobyname
getprotobynumber getservbyname getservbyport
getsockname getsockopt htonl
htons inet_addr inet_ntoa
ioctlsocket listen ntohl
ntohs recv select
send sendto setsockopt
shutdown socket TransmitFile
WSAAsyncGetHostByName WSAAsyncGetProtoByName WSAAsyncGetProtoByNumber
WSAAsyncGetServByName WSAAsyncGetServByPort WSAAsyncSelect
WSACancelAsyncRequest WSACancelBlockingCall WSACleanup
WSAGetLastError WSAIsBlocking WSARecvEx
WSASetBlockingHook WSASetLastError WSAStartup333
Chapter 22. Messages
This chapter describes the various messages that the compiler produces. These messages include the sign-on
message and diagnostic messages for remarks, warnings, and errors. The compiler always displays any error
messages, along with the erroneous source line, on the screen. If you specify the –Mlist option, the compiler
places any error messages in the listing file. You can also use the –v option to display more information about
the compiler, assembler, and linker invocations and about the host system. For more information on the
–Mlist and –v options, refer to Chapter 2, “Using Command Line Options”.
Diagnostic Messages
Diagnostic messages provide syntactic and semantic information about your source text. Syntactic information
includes information such as syntax errors. Semantic includes in-formation includes such as unreachable
code.
You can specify that the compiler displays error messages at a certain level with the -Minform option.
The compiler messages refer to a severity level, a message number, and the line number where the error
occurs.
The compiler can also display internal error messages on standard errors. If your compilation produces
any internal errors, contact The Portland Group’s technical reporting service by sending e-mail to
trs@pgroup.com.
If you use the listing file option –Mlist, the compiler places diagnostic messages after the source lines in the
listing file, in the following format:
PGFTN-etype-enum-message (filename: line)
Where:
etype
is a character signifying the severity level
enum
is the error number
message
is the error messagePGI® User’s Guide
334
filename
is the source filename
line
is the line number where the compiler detected an error.
Phase Invocation Messages
You can display compiler, assembler, and linker phase invocations by using the –v command line option. For
further information about this option, see Chapter 2, “Using Command Line Options”.
Fortran Compiler Error Messages
This section presents the error messages generated by the PGF77 and PGF95 compilers. The compilers display
error messages in the program listing and on standard output; and can also display internal error messages on
standard error.
Message Format
Each message is numbered. Each message also lists the line and column number where the error occurs. A
dollar sign ($) in a message represents information that is specific to each occurrence of the message.
Message List
Error message severities:
I
informative
W
warning
S
severe error
F
fatal error
V
variable
V000 Internal compiler error. $ $
This message indicates an error in the compiler, rather than a user error – although it may be possible for a
user error to cause an internal error. The severity may vary; if it is informative or warning, correct object code
was probably generated, but it is not safe to rely on this. Regardless of the severity or cause, internal errors
should be reported to trs@pgroup.com.
F001 Source input file name not specified
On the command line, source file name should be specified either before all the switches, or after them.
F002 Unable to open source input file: $
Source file name misspelled, file not in current working directory, or file is read protected.Chapter 22. Messages
335
F003 Unable to open listing file
Probably, user does not have write permission for the current working directory.
F004 $ $
Generic message for file errors.
F005 Unable to open temporary file
Compiler uses directory "/usr/tmp" or "/tmp" in which to create temporary files. If neither of these directories
is available on the node on which the compiler is being used, this error will occur.
S006 Input file empty
Source input file does not contain any Fortran statements other than comments or compiler directives.
F007 Subprogram too large to compile at this optimization level
$
Internal compiler data structure overflow, working storage exhausted, or some other non-recoverable
problem related to the size of the subprogram. If this error occurs at opt 2, reducing the opt level to 1 may
work around the problem. Moving the subprogram being compiled to its own source file may eliminate
the problem. If this error occurs while compiling a subprogram of fewer than 2000 statements it should be
reported to the compiler maintenance group as a possible compiler problem.
F008 Error limit exceeded
The compiler gives up because too many severe errors were issued; the error limit can be reset on the
command line.
F009 Unable to open assembly file
Probably, user does not have write permission for the current working directory.
F010 File write error occurred $
Probably, file system is full.
S011 Unrecognized command line switch: $
Refer to PDS reference document for list of allowed compiler switches.
S012 Value required for command line switch: $
Certain switches require an immediately following value, such as "-opt 2".
V000 Internal compiler error. $ $
This message indicates an error in the compiler, rather than a user error – although it may be possible for a
user error to cause an internal error. The severity may vary; if it is informative or warning, correct object code
was probably generated, but it is not safe to rely on this. Regardless of the severity or cause, internal errors
should be reported to trs@pgroup.com.
F001 Source input file name not specified
On the command line, source file name should be specified either before all the switches, or after them.
F002 Unable to open source input file: $
Source file name misspelled, file not in current working directory, or file is read protected.
F003 Unable to open listing file
Probably, user does not have write permission for the current working directory.PGI® User’s Guide
336
F004 $ $
Generic message for file errors.
F005 Unable to open temporary file
Compiler uses directory "/usr/tmp" or "/tmp" in which to create temporary files. If neither of these directories
is available on the node on which the compiler is being used, this error will occur.
S006 Input file empty
Source input file does not contain any Fortran statements other than comments or compiler directives.
F007 Subprogram too large to compile at this optimization level
$
Internal compiler data structure overflow, working storage exhausted, or some other non-recoverable
problem related to the size of the subprogram. If this error occurs at opt 2, reducing the opt level to 1 may
work around the problem. Moving the subprogram being compiled to its own source file may eliminate
the problem. If this error occurs while compiling a subprogram of fewer than 2000 statements it should be
reported to the compiler maintenance group as a possible compiler problem.
F008 Error limit exceeded
The compiler gives up because too many severe errors were issued; the error limit can be reset on the
command line.
F009 Unable to open assembly file
Probably, user does not have write permission for the current working directory.
F010 File write error occurred $
Probably, file system is full.
S011 Unrecognized command line switch: $
Refer to PDS reference document for list of allowed compiler switches.
S012 Value required for command line switch: $
Certain switches require an immediately following value, such as "-opt 2".
S013 Unrecognized value specified for command line switch: $
S014 Ambiguous command line switch: $
Too short an abbreviation was used for one of the switches.
W015 Hexadecimal or octal constant truncated to fit data type
I016 Identifier, $, truncated to 31 chars
An identifier may be at most 31 characters in length; characters after the 31st are ignored.
S017 Unable to open include file: $
File is missing, read protected, or maximum include depth (10) exceeded. Remember that the file name
should be enclosed in quotes.
S018 Illegal label $ $
Used for label ’field’ errors or illegal values. E.g., in fixed source form, the label field (first five characters) of
the indicated line contains a non-numeric character.Chapter 22. Messages
337
S019 Illegally placed continuation line
A continuation line does not follow an initial line, or more than 99 continuation lines were specified.
S020 Unrecognized compiler directive
Refer to user’s manual for list of allowed compiler directives.
S021 Label field of continuation line is not blank
The first five characters of a continuation line must be blank.
S022 Unexpected end of file - missing END statement
S023 Syntax error - unbalanced $
Unbalanced parentheses or brackets.
W024 CHARACTER or Hollerith constant truncated to fit data type
A character or hollerith constant was converted to a data type that was not large enough to contain all of the
characters in the constant. This type conversion occurs when the constant is used in an arithmetic expression
or is assigned to a non-character variable. The character or hollerith constant is truncated on the right, that is,
if 4 characters are needed then the first 4 are used and the remaining characters are discarded.
W025 Illegal character ($) - ignored
The current line contains a character, possibly non-printing, which is not a legal Fortran character (characters
inside of character or Hollerith constants cannot cause this error). As a general rule, all non-printing
characters are treated as white space characters (blanks and tabs); no error message is generated when
this occurs. If for some reason, a non-printing character is not treated as a white space character, its hex
representation is printed in the form dd where each d is a hex digit.
S026 Unmatched quote
S027 Illegal integer constant: $
Integer constant is too large for 32 bit word.
S028 Illegal real or double precision constant: $
S029 Illegal $ constant: $
Illegal hexadecimal, octal, or binary constant. A hexadecimal constant consists of digits 0..9 and letters A..F or
a..f; any other character in a hexadecimal constant is illegal. An octal constant consists of digits 0..7; any other
digit or character in an octal constant is illegal. A binary constant consists of digits 0 or 7; any other digit or
character in a binary constant is illegal.
S030 Explicit shape must be specified for $
S031 Illegal data type length specifier for $
The data type length specifier (e.g. 4 in INTEGER*4) is not a constant expression that is a member of the set of
allowed values for this particular data type.
W032 Data type length specifier not allowed for $
The data type length specifier (e.g. 4 in INTEGER*4) is not allowed in the given syntax (e.g. DIMENSION
A(10)*4).
S033 Illegal use of constant $
A constant was used in an illegal context, such as on the left side of an assignment statement or as the target of
a data initialization statement.PGI® User’s Guide
338
S034 Syntax error at or near $
I035 Predefined intrinsic $ loses intrinsic property
An intrinsic name was used in a manner inconsistent with the language definition for that intrinsic. The
compiler, based on the context, will treat the name as a variable or an external function.
S036 Illegal implicit character range
First character must alphabetically precede second.
S037 Contradictory data type specified for $
The indicated identifier appears in more than one type specification statement and different data types are
specified for it.
S038 Symbol, $, has not been explicitly declared
The indicated identifier must be declared in a type statement; this is required when the IMPLICIT NONE
statement occurs in the subprogram.
W039 Symbol, $, appears illegally in a SAVE statement $
An identifier appearing in a SAVE statement must be a local variable or array.
S040 Illegal common variable $
Indicated identifier is a dummy variable, is already in a common block, or has previously been defined to be
something other than a variable or array.
W041 Illegal use of dummy argument $
This error can occur in several situations. It can occur if dummy arguments were specified on a PROGRAM
statement. It can also occur if a dummy argument name occurs in a DATA, COMMON, SAVE, or EQUIVALENCE
statement. A program statement must have an empty argument list.
S042 $ is a duplicate dummy argument
S043 Illegal attempt to redefine $ $
An attempt was made to define a symbol in a manner inconsistent with an earlier definition of the same
symbol. This can happen for a number of reasons. The message attempts to indicate the situation that
occurred.
intrinsic - An attempt was made to redefine an intrinsic function. A symbol that represents an intrinsic function
may be redefined if that symbol has not been previously verified to be an intrinsic function. For example, the
intrinsic sin can be defined to be an integer array. If a symbol is verified to be an intrinsic function via the
INTRINSIC statement or via an intrinsic function reference then it must be referred to as an intrinsic function
for the remainder of the program unit.
symbol - An attempt was made to redefine a symbol that was previously defined. An example of this is to
declare a symbol to be a PARAMETER which was previously declared to be a subprogram argument.
S044 Multiple declaration for symbol $
A redundant declaration of a symbol has occurred. For example, an attempt was made to declare a symbol as
an ENTRY when that symbol was previously declared as an ENTRY.
S045 Data type of entry point $ disagrees with function $
The current function has entry points with data types inconsistent with the data type of the current function. For
example, the function returns type character and an entry point returns type complex.Chapter 22. Messages
339
S046 Data type length specifier in wrong position
The CHARACTER data type specifier has a different position for the length specifier from the other data types.
Suppose, we want to declare arrays ARRAYA and ARRAYB to have 8 elements each having an element length
of 4 bytes. The difference is that ARRAYA is character and ARRAYB is integer. The declarations would be
CHARACTER ARRAYA(8)*4 and INTEGER ARRAYB*4(8).
S047 More than seven dimensions specified for array
S048 Illegal use of ’*’ in declaration of array $
An asterisk may be used only as the upper bound of the last dimension.
S049 Illegal use of ’*’ in non-subroutine subprogram
The alternate return specifier ’*’ is legal only in the subroutine statement. Programs, functions, and block data
are not allowed to have alternate return specifiers.
S050 Assumed size array, $, is not a dummy argument
S051 Unrecognized built-in % function
The allowable built-in functions are %VAL, %REF, %LOC, and %FILL. One was encountered that did not match
one of these allowed forms.
S052 Illegal argument to %VAL or %LOC
S053 %REF or %VAL not legal in this context
The built-in functions %REF and %VAL can only be used as actual parameters in procedure calls.
W054 Implicit character $ used in a previous implicit statement
An implicit character has been given an implied data type more than once. The implied data type for the
implicit character is changed anyway.
W055 Multiple implicit none statements
The IMPLICIT NONE statement can occur only once in a subprogram.
W056 Implicit type declaration
The -Mdclchk switch and an implicit declaration following an IMPLICIT NONE statement will produce a
warning message for IMPLICIT statements.
S057 Illegal equivalence of dummy variable, $
Dummy arguments may not appear in EQUIVALENCE statements.
S058 Equivalenced variables $ and $ not in same common block
A common block variable must not be equivalenced with a variable in another common block.
S059 Conflicting equivalence between $ and $
The indicated equivalence implies a storage layout inconsistent with other equivalences.
S060 Illegal equivalence of structure variable, $
STRUCTURE and UNION variables may not appear in EQUIVALENCE statements.
S061 Equivalence of $ and $ extends common block backwards
W062 Equivalence forces $ to be unaligned
EQUIVALENCE statements have defined an address for the variable which has an alignment not optimal for
variables of its data type. This can occur when INTEGER and CHARACTER data are equivalenced, for instance.PGI® User’s Guide
340
I063 Gap in common block $ before $
S064 Illegal use of $ in DATA statement implied DO loop
The indicated variable is referenced where it is not an active implied DO index variable.
S065 Repeat factor less than zero
S066 Too few data constants in initialization statement
S067 Too many data constants in initialization statement
S068 Numeric initializer for CHARACTER $ out of range 0 through
255
A CHARACTER*1 variable or character array element can be initialized to an integer, octal, or hexadecimal
constant if that constant is in the range 0 through 255.
S069 Illegal implied DO expression
The only operations allowed within an implied DO expression are integer +, -, *, and /.
S070 Incorrect sequence of statements $
The statement order is incorrect. For instance, an IMPLICIT NONE statement must precede a specification
statement which in turn must precede an executable statement.
S071 Executable statements not allowed in block data
S072 Assignment operation illegal to $ $
The destination of an assignment operation must be a variable, array reference, or vector reference. The
assignment operation may be by way of an assignment statement, a data statement, or the index variable of
an implied DO-loop. The compiler has determined that the identifier used as the destination, is not a storage
location. The error message attempts to indicate the type of entity used.
entry point - An assignment to an entry point that was not a function procedure was attempted.
external procedure - An assignment to an external procedure or a Fortran intrinsic name was attempted. if the
identifier is the name of an entry point that is not a function, an external procedure...
S073 Intrinsic or predeclared, $, cannot be passed as an
argument
S074 Illegal number or type of arguments to $ $
The indicated symbol is an intrinsic or generic function, or a predeclared subroutine or function, requiring a
certain number of arguments of a fixed data type.
S075 Subscript, substring, or argument illegal in this context
for $
This can happen if you try to doubly index an array such as ra(2)(3). This also applies to substring and
function references.
S076 Subscripts specified for non-array variable $
S077 Subscripts omitted from array $
S078 Wrong number of subscripts specified for $
S079 Keyword form of argument illegal in this context for $$Chapter 22. Messages
341
S080 Subscript for array $ is out of bounds
S081 Illegal selector $ $
S082 Illegal substring expression for variable $
Substring expressions must be of type integer and if constant must be greater than zero.
S083 Vector expression used where scalar expression required
A vector expression was used in an illegal context. For example, iscalar = iarray, where a scalar is assigned the
value of an array. Also, character and record references are not vectorizable.
S084 Illegal use of symbol $ $
This message is used for many different errors.
S085 Incorrect number of arguments to statement function $
S086 Dummy argument to statement function must be a variable
S087 Non-constant expression where constant expression required
S088 Recursive subroutine or function call of $
A function may not call itself.
S089 Illegal use of symbol, $, with character length = *
Symbols of type CHARACTER*(*) must be dummy variables and must not be used as statement function dummy
parameters and statement function names. Also, a dummy variable of type CHARACTER*(*) cannot be used as
a function.
S090 Hollerith constant more than 4 characters
In certain contexts, Hollerith constants may not be more than 4 characters long.
S091 Constant expression of wrong data type
S092 Illegal use of variable length character expression
A character expression used as an actual argument, or in certain contexts within I/O statements, must not
consist of a concatenation involving a passed length character variable.
W093 Type conversion of expression performed
An expression of some data type appears in a context which requires an expression of some other data type.
The compiler generates code to convert the expression into the required type.
S094 Variable $ is of wrong data type $
The indicated variable is used in a context which requires a variable of some other data type.
S095 Expression has wrong data type
An expression of some data type appears in a context which requires an expression of some other data type.
S096 Illegal complex comparison
The relations .LT., .GT., .GE., and .LE. are not allowed for complex values.
S097 Statement label $ has been defined more than once
More than one statement with the indicated statement number occurs in the subprogram.
S098 Divide by zeroPGI® User’s Guide
342
S099 Illegal use of $
Aggregate record references may only appear in aggregate assignment statements, unformatted I/O statements,
and as parameters to subprograms. They may not appear, for example, in expressions. Also, records with
differing structure types may not be assigned to one another.
S100 Expression cannot be promoted to a vector
An expression was used that required a scalar quantity to be promoted to a vector illegally. For example, the
assignment of a character constant string to a character array. Records, too, cannot be promoted to vectors.
S101 Vector operation not allowed on $
Record and character typed entities may only be referenced as scalar quantities.
S102 Arithmetic IF expression has wrong data type
The parenthetical expression of an arithmetic if statement must be an integer, real, or double precision scalar
expression.
S103 Type conversion of subscript expression for $
The data type of a subscript expression must be integer. If it is not, it is converted.
S104 Illegal control structure $
This message is issued for a number of errors involving IF-THEN statements and DO loops. If the line number
specified is the last line (END statement) of the subprogram, the error is probably an unterminated DO loop or
IF-THEN statement.
S105 Unmatched ELSEIF, ELSE or ENDIF statement
An ELSEIF, ELSE, or ENDIF statement cannot be matched with a preceding IF-THEN statement.
S106 DO index variable must be a scalar variable
The DO index variable cannot be an array name, a subscripted variable, a PARAMETER name, a function name,
a structure name, etc.
S107 Illegal assigned goto variable $
S108 Illegal variable, $, in NAMELIST group $
A NAMELIST group can only consist of arrays and scalars which are not dummy arguments and pointer-based
variables.
I109 Overflow in $ constant $, constant truncated at left
A non-decimal (hexadecimal, octal, or binary) constant requiring more than 64-bits produces an overflow.
The constant is truncated at left (e.g. ’1234567890abcdef1’x will be ’234567890abcdef1’x).
I110
I111 Underflow of real or double precision constant
I112 Overflow of real or double precision constant
S113 Label $ is referenced but never defined
S114 Cannot initialize $
W115 Assignment to DO variable $ in loop
S116 Illegal use of pointer-based variable $ $Chapter 22. Messages
343
S117 Statement not allowed within a $ definition
The statement may not appear in a STRUCTURE or derived type definition.
S118 Statement not allowed in DO, IF, or WHERE block
I119 Redundant specification for $
Data type of indicated symbol specified more than once.
I120 Label $ is defined but never referenced
I121 Operation requires logical or integer data types
An operation in an expression was attempted on data having a data type incompatible with the operation. For
example, a logical expression can consist of only logical elements of type integer or logical. Real data would be
invalid.
I122 Character string truncated
Character string or Hollerith constant appearing in a DATA statement or PARAMETER statement has been
truncated to fit the declared size of the corresponding identifier.
W123 Hollerith length specification too big, reduced
The length specifier field of a hollerith constant specified more characters than were present in the character
field of the hollerith constant. The length specifier was reduced to agree with the number of characters
present.
S124 Relational expression mixes character with numeric data
A relational expression is used to compare two arithmetic expressions or two character expressions. A
character expression cannot be compared to an arithmetic expression.
I125 Dummy procedure $ not declared EXTERNAL
A dummy argument which is not declared in an EXTERNAL statement is used as the subprogram name in a
CALL statement, or is called as a function, and is therefore assumed to be a dummy procedure. This message
can result from a failure to declare a dummy array.
I126 Name $ is not an intrinsic function
I127 Optimization level for $ changed to opt 1 $
W128 Integer constant truncated to fit data type: $
An integer constant will be truncated when assigned to data types smaller than 32-bits, such as a BYTE.
I129 Floating point overflow. Check constants and constant
expressions
I130 Floating point underflow. Check constants and constant
expressions
I131 Integer overflow. Check floating point expressions cast to
integer
I132 Floating pt. invalid oprnd. Check constants and constant
expressions
I133 Divide by 0.0. Check constants and constant expressionsPGI® User’s Guide
344
S134 Illegal attribute $ $
W135 Missing STRUCTURE name field
A STRUCTURE name field is required on the outermost structure.
W136 Field-namelist not allowed
The field-namelist field of the STRUCTURE statement is disallowed on the outermost structure.
W137 Field-namelist is required in nested structures
W138 Multiply defined STRUCTURE member name $
A member name was used more than once within a structure.
W139 Structure $ in RECORD statement not defined
A RECORD statement contains a reference to a STRUCTURE that has not yet been defined.
S140 Variable $ is not a RECORD
S141 RECORD required on left of $
S142 $ is not a member of this RECORD
S143 $ requires initializer
W144 NEED ERROR MESSAGE $ $
This is used as a temporary message for compiler development.
W145 %FILL only valid within STRUCTURE block
The %FILL special name was used outside of a STRUCTURE multiline statement. It is only valid when used
within a STRUCTURE multiline statement even though it is ignored.
S146 Expression must be character type
S147 Character expression not allowed in this context
S148 Reference to $ required
An aggregate reference to a record was expected during statement compilation but another data type was
found instead.
S149 Record where arithmetic value required
An aggregate record reference was encountered when an arithmetic expression was expected.
S150 Structure, Record, derived type, or member $ not allowed
in this context
A structure, record, or member reference was found in a context which is not supported. For example, the use
of structures, records, or members within a data statement is disallowed.
S151 Empty TYPE, STRUCTURE, UNION, or MAP
TYPE - ENDTYPE, STRUCTURE - ENDSTRUCTURE, UNION - ENDUNION MAP - ENDMAP declaration contains no
members.
S152 All dimension specifiers must be ’:’
S153 Array objects are not conformable $
S154 DISTRIBUTE target, $, must be a processorChapter 22. Messages
345
S155 $ $
S156 Number of colons and triplets must be equal in ALIGN $
with $
S157 Illegal subscript use of ALIGN dummy $ - $
S158 Alternate return not specified in SUBROUTINE or ENTRY
An alternate return can only be used if alternate return specifiers appeared in the SUBROUTINE or ENTRY
statements.
S159 Alternate return illegal in FUNCTION subprogram
An alternate return cannot be used in a FUNCTION.
S160 ENDSTRUCTURE, ENDUNION, or ENDMAP does not match top
S161 Vector subscript must be rank-one array
W162 Not equal test of loop control variable $ replaced with <
or > test.
S163
S164 Overlapping data initializations of $
An attempt was made to data initialize a variable or array element already initialized.
S165 $ appeared more than once as a subprogram
A subprogram name appeared more than once in the source file. The message is applicable only when an
assembly file is the output of the compiler.
S166 $ cannot be a common block and a subprogram
A name appeared as a common block name and a subprogram name. The message is applicable only when an
assembly file is the output of the compiler.
I167 Inconsistent size of common block $
A common block occurs in more than one subprogram of a source file and its size is not identical. The
maximum size is chosen. The message is applicable only when an assembly file is the output of the compiler.
S168 Incompatible size of common block $
A common block occurs in more than one subprogram of a source file and is initialized in one subprogram.
Its initialized size was found to be less than its size in the other subprogram(s). The message is applicable only
when an assembly file is the output of the compiler.
W169 Multiple data initializations of common block $
A common block is initialized in more than one subprogram of a source file. Only the first set of initializations
apply. The message is applicable only when an assembly file is the output of the compiler.
W170 F90 extension: $ $
Use of a nonstandard feature. A description of the feature is provided.
W171 F90 extension: nonstandard statement type $
W172 F90 extension: numeric initialization of CHARACTER $
A CHARACTER*1 variable or array element was initialized with a numeric value.PGI® User’s Guide
346
W173 F90 extension: nonstandard use of data type length
specifier
W174 F90 extension: type declaration contains data
initialization
W175 F90 extension: IMPLICIT range contains nonalpha characters
W176 F90 extension: nonstandard operator $
W177 F90 extension: nonstandard use of keyword argument $
W178
W179 F90 extension: use of structure field reference $
W180 F90 extension: nonstandard form of constant
W181 F90 extension: & alternate return
W182 F90 extension: mixed non-character and character elements
in COMMON $
W183 F90 extension: mixed non-character and character
EQUIVALENCE ($,$)
W184 Mixed type elements (numeric and/or character types) in
COMMON $
W185 Mixed numeric and/or character type EQUIVALENCE ($,$)
S186 Argument missing for formal argument $
S187 Too many arguments specified for $
S188 Argument number $ to $: type mismatch
S189 Argument number $ to $: association of scalar actual
argument to array dummy argument
S190 Argument number $ to $: non-conformable arrays
S191 Argument number $ to $ cannot be an assumed-size array
S192 Argument number $ to $ must be a label
W193 Argument number $ to $ does not match INTENT (OUT)
W194 INTENT(IN) argument cannot be defined - $
S195 Statement may not appear in an INTERFACE block $
S196 Deferred-shape specifiers are required for $
S197 Invalid qualifier or qualifier value (/$) in OPTIONS
statement
An illegal qualifier was found or a value was specified for a qualifier which does not expect a value. In either
case, the qualifier for which the error occurred is indicated in the error message.Chapter 22. Messages
347
S198 $ $ in ALLOCATE/DEALLOCATE
W199 Unaligned memory reference
A memory reference occurred whose address does not meet its data alignment requirement.
S200 Missing UNIT/FILE specifier
S201 Illegal I/O specifier - $
S202 Repeated I/O specifier - $
S203 FORMAT statement has no label
S204 $ $
Miscellaneous I/O error.
S205 Illegal specification of scale factor
The integer following + or - has been omitted, or P does not follow the integer value.
S206 Repeat count is zero
S207 Integer constant expected in edit descriptor
S208 Period expected in edit descriptor
S209 Illegal edit descriptor
S210 Exponent width not used in the Ew.dEe or Gw.dEe edit
descriptors
S211 Internal I/O not allowed in this I/O statement
S212 Illegal NAMELIST I/O
Namelist I/O cannot be performed with internal, unformatted, formatted, and list-directed I/O. Also, I/O lists
must not be present.
S213 $ is not a NAMELIST group name
S214 Input item is not a variable reference
S215 Assumed sized array name cannot be used as an I/O item or
specifier
An assumed sized array was used as an item to be read or written or as an I/O specifier (i.e., FMT = arrayname). In these contexts the size of the array must be known.
S216 STRUCTURE/UNION cannot be used as an I/O item
S217 ENCODE/DECODE buffer must be a variable, array, or array
element
S218 Statement labeled $ $
S219
S220 Redefining predefined macro $PGI® User’s Guide
348
S221 #elif after #else
A preprocessor #elif directive was found after a #else directive; only #endif is allowed in this context.
S222 #else after #else
A preprocessor #else directive was found after a #else directive; only #endif is allowed in this context.
S223 #if-directives too deeply nested
Preprocessor #if directive nesting exceeded the maximum allowed (currently 10).
S224 Actual parameters too long for $
The total length of the parameters in a macro call to the indicated macro exceeded the maximum allowed
(currently 2048).
W225 Argument mismatch for $
The number of arguments supplied in the call to the indicated macro did not agree with the number of
parameters in the macro’s definition.
F226 Can’t find include file $
The indicated include file could not be opened.
S227 Definition too long for $
The length of the macro definition of the indicated macro exceeded the maximum allowed (currently 2048).
S228 EOF in comment
The end of a file was encountered while processing a comment.
S229 EOF in macro call to $
The end of a file was encountered while processing a call to the indicated macro.
S230 EOF in string
The end of a file was encountered while processing a quoted string.
S231 Formal parameters too long for $
The total length of the parameters in the definition of the indicated macro exceeded the maximum allowed
(currently 2048).
S232 Identifier too long
The length of an identifier exceeded the maximum allowed (currently 2048).
S233
W234 Illegal directive name
The sequence of characters following a # sign was not an identifier.
W235 Illegal macro name
A macro name was not an identifier.
S236 Illegal number $
The indicated number contained a syntax error.
F237 Line too long
The input source line length exceeded the maximum allowed (currently 2048).Chapter 22. Messages
349
W238 Missing #endif
End of file was encountered before a required #endif directive was found.
W239 Missing argument list for $
A call of the indicated macro had no argument list.
S240 Number too long
The length of a number exceeded the maximum allowed (currently 2048).
W241 Redefinition of symbol $
The indicated macro name was redefined.
I242 Redundant definition for symbol $
A definition for the indicated macro name was found that was the same as a previous definition.
F243 String too long
The length of a quoted string exceeded the maximum allowed (currently 2048).
S244 Syntax error in #define, formal $ not identifier
A formal parameter that was not an identifier was used in a macro definition.
W245 Syntax error in #define, missing blank after name or
arglist
There was no space or tab between a macro name or argument list and the macro’s definition.
S246 Syntax error in #if
A syntax error was found while parsing the expression following a #if or #elif directive.
S247 Syntax error in #include
The #include directive was not correctly formed.
W248 Syntax error in #line
A #line directive was not correctly formed.
W249 Syntax error in #module
A #module directive was not correctly formed.
W250 Syntax error in #undef
A #undef directive was not correctly formed.
W251 Token after #ifdef must be identifier
The #ifdef directive was not followed by an identifier.
W252 Token after #ifndef must be identifier
The #ifndef directive was not followed by an identifier.
S253 Too many actual parameters to $
The number of actual arguments to the indicated macro exceeded the maximum allowed (currently 31).
S254 Too many formal parameters to $
The number of formal arguments to the indicated macro exceeded the maximum allowed (currently 31).
F255 Too much pushback
The preprocessor ran out of space while processing a macro expansion. The macro may be recursive.PGI® User’s Guide
350
W256 Undefined directive $
The identifier following a # was not a directive name.
S257 EOF in #include directive
End of file was encountered while processing a #include directive.
S258 Unmatched #elif
A #elif directive was encountered with no preceding #if or #elif directive.
S259 Unmatched #else
A #else directive was encountered with no preceding #if or #elif directive.
S260 Unmatched #endif
A #endif directive was encountered with no preceding #if, #ifdef, or #ifndef directive.
S261 Include files nested too deeply
The nesting depth of #include directives exceeded the maximum (currently 20).
S262 Unterminated macro definition for $
A newline was encountered in the formal parameter list for the indicated macro.
S263 Unterminated string or character constant
A newline with no preceding backslash was found in a quoted string.
I264 Possible nested comment
The characters /* were found within a comment.
S265
S266
S267
W268 Cannot inline subprogram; common block mismatch
W269 Cannot inline subprogram; argument type mismatch
This message may be Severe if have gone too far to undo inlining process.
F270 Missing -exlib option
W271 Can’t inline $ - wrong number of arguments
I272 Argument of inlined function not used
S273 Inline library not specified on command line (-inlib
switch)
F274 Unable to access file $/TOC
S275 Unable to open file $ while extracting or inlining
F276 Assignment to constant actual parameter in inlined
subprogram
I277 Inlining of function $ may result in recursion
S278 Chapter 22. Messages
351
W279 Possible use of $ before definition in $
The optimizer has detected the possibility that a variable is used before it has been assigned a value. The names
of the variable and the function in which the use occurred are listed. The line number, if specified, is the line
number of the basic block containing the use of the variable.
W280 Syntax error in directive $
messages 280-300 rsvd for directive handling
W281 Directive ignored - $ $
S300 Too few data constants in initialization of derived type $
S301 $ must be TEMPLATE or PROCESSOR
S302 Unmatched END$ statement
S303 END statement for $ required in an interface block
S304 EXIT/CYCLE statement must appear in a DO/DOWHILE loop$$
S305 $ cannot be named, $
S306 $ names more than one construct
S307 $ must have the construct name $
S308 DO may not terminate at an EXIT, CYCLE, RETURN, STOP,
GOTO, or arithmetic IF
S309 Incorrect name, $, specified in END statement
S310 $ $
Generic message for MODULE errors.
W311 Non-replicated mapping for $ array, $, ignored
W312 Array $ should be declared SEQUENCE
W313 Subprogram $ called within INDEPENDENT loop not PURE
E314 IPA: actual argument $ is a label, but dummy argument $ is
not an asterisk
The call passes a label to the subprogram; the corresponding dummy argument in the subprogram should be
an asterisk to declare this as the alternate return.
I315 IPA: routine $, $ constant dummy arguments
This many dummy arguments are being replaced by constants due to interprocedural analysis.
I316 IPA: routine $, $ INTENT(IN) dummy arguments
This many dummy arguments are being marked as INTENT(IN) due to interprocedural analysis.
I317 IPA: routine $, $ array alignments propagated
This many array alignments were propagated by interprocedural analysis.
I318 IPA: routine $, $ distribution formats propagated
This many array distribution formats were propagated by interprocedural analysis.PGI® User’s Guide
352
I319 IPA: routine $, $ distribution targets propagated
This many array distribution targets were propagated by interprocedural analysis.
I320 IPA: routine $, $ common blocks optimized
This many mapped common blocks were optimized by interprocedural analysis.
I321 IPA: routine $, $ common blocks not optimized
This many mapped common blocks were not optimized by interprocedural analysis, either because they were
declared differently in different routines, or they did not appear in the main program.
I322 IPA: analyzing main program $
Interprocedural analysis is building the call graph and propagating information with the named main program.
I323 IPA: collecting information for $
Interprocedural analysis is saving information for the current subprogram for subsequent analysis and
propagation.
W324 IPA file $ appears to be out of date
W325 IPA file $ is for wrong subprogram: $
W326 Unable to open file $ to propagate IPA information to $
I327 IPA: $ subprograms analyzed
I328 IPA: $ dummy arguments replaced by constants
I329 IPA: $ INTENT(IN) dummy arguments should be INTENT(INOUT)
I330 IPA: $ dummy arguments changed to INTENT(IN)
I331 IPA: $ inherited array alignments replaced
I332 IPA: $ transcriptive distribution formats replaced
I333 IPA: $ transcriptive distribution targets replaced
I334 IPA: $ descriptive/prescriptive array alignments verified
I335 IPA: $ descriptive/prescriptive distribution formats
verified
I336 IPA: $ descriptive/prescriptive distribution targets
verified
I337 IPA: $ common blocks optimized
I338 IPA: $ common blocks not optimized
S339 Bad IPA contents file: $
S340 Bad IPA file format: $
S341 Unable to create file $ while analyzing IPA information
S342 Unable to open file $ while analyzing IPA information
S343 Unable to open IPA contents file $Chapter 22. Messages
353
S344 Unable to create file $ while collecting IPA information
F345 Internal error in $: table overflow
Analysis failed due to a table overflowing its maximum size.
W346 Subprogram $ appears twice
The subprogram appears twice in the same source file; IPA will ignore the first appearance.
F347 Missing -ipalib option
Interprocedural analysis, enabled with the -ipacollect, -ipaanalyze, or -ipapropagate options, requires the -
ipalib option to specify the library directory.
W348 Common /$/ $ has different distribution target
The array was declared in a common block with a different distribution target in another subprogram.
W349 Common /$/ $ has different distribution format
The array was declared in a common block with a different distribution format in another subprogram.
W350 Common /$/ $ has different alignment
The array was declared in a common block with a different alignment in another subprogram.
W351 Wrong number of arguments passed to $
The subroutine or function statement for the given subprogram has a different number of dummy arguments
than appear in the call.
W352 Wrong number of arguments passed to $ when bound to $
The subroutine or function statement for the given subprogram has a different number of dummy arguments
than appear in the call to the EXTERNAL name given.
W353 Subprogram $ is missing
A call to a subroutine or function with this name appears, but it could not be found or analyzed.
I354 Subprogram $ is not called
No calls to the given subroutine or function appear anywhere in the program.
W355 Missing argument in call to $
A nonoptional argument is missing in a call to the given subprogram.
I356 Array section analysis incomplete
Interprocedural analysis for array section arguments is incomplete; some information may not be available for
optimization.
I357 Expression analysis incomplete
Interprocedural analysis for expression arguments is incomplete; some information may not be available for
optimization.
W358 Dummy argument $ is EXTERNAL, but actual is not subprogram
The call statement passes a scalar or array to a dummy argument that is declared EXTERNAL.
W359 SUBROUTINE $ passed to FUNCTION dummy argument $
The call statement passes a subroutine name to a dummy argument that is used as a function.PGI® User’s Guide
354
W360 FUNCTION $ passed to FUNCTION dummy argument $ with
different result type
The call statement passes a function argument to a function dummy argument, but the dummy has a different
result type.
W361 FUNCTION $ passed to SUBROUTINE dummy argument $
The call statement passes a function name to a dummy argument that is used as a subroutine.
W362 Argument $ has a different type than dummy argument $
The type of the actual argument is different than the type of the corresponding dummy argument.
W363 Dummy argument $ is a POINTER but actual argument $ is not
The dummy argument is a pointer, so the actual argument must be also.
W364 Array or array expression passed to scalar dummy argument
$
The actual argument is an array, but the dummy argument is a scalar variable.
W365 Scalar or scalar expression passed to array dummy argument
$
The actual argument is a scalar variable, but the dummy argument is an array.
F366 Internal error: interprocedural analysis fails
An internal error occurred during interprocedural analysis; please report this to the compiler maintenance
group. If user errors were reported when collecting IPA information or during IPA analysis, correcting them
may avoid this error.
I367 Array $ bounds cannot be matched to formal argument
Passing a nonsequential array to a sequential dummy argument may require copying the array to sequential
storage. The most common cause is passing an ALLOCATABLE array or array expression to a dummy argument
that is declared with explicit bounds. Declaring the dummy argument as assumed shape, with bounds (:,:,:),
will remove this warning.
W368 Array-valued expression passed to scalar dummy argument $
The actual argument is an array-valued expression, but the dummy argument is a scalar variable.
W369 Dummy argument $ has different rank than actual argument
The actual argument is an array or array-valued expression with a different rank than the dummy argument.
W370 Dummy argument $ has different shape than actual argument
The actual argument is an array or array-valued expression with a different shape than the dummy argument;
this may require copying the actual argument into sequential storage.
W371 Dummy argument $ is INTENT(IN) but may be modified
The dummy argument was declared as INTENT(IN), but analysis has found that the argument may be modified;
the INTENT(IN) declaration should be changed.
W372 Cannot propagate alignment from $ to $
The most common cause is when passing an array with an inherited alignment to a dummy argument with noninherited alignment.Chapter 22. Messages
355
I373 Cannot propagate distribution format from $ to $
The most common cause is when passing an array with a transcriptive distribution format to a dummy
argument with prescriptive or descriptive distribution format.
I374 Cannot propagate distribution target from $ to $
The most common cause is when passing an array with a transcriptive distribution target to a dummy argument
with prescriptive or descriptive distribution target.
I375 Distribution format mismatch between $ and $
Usually this arises when the actual and dummy arguments are distributed in different dimensions.
I376 Alignment stride mismatch between $ and $
This may arise when the actual argument has a different stride in its alignment to its template than does the
dummy argument.
I377 Alignment offset mismatch between $ and $
This may arise when the actual argument has a different offset in its alignment to its template than does the
dummy argument.
I378 Distribution target mismatch between $ and $
This may arise when the actual and dummy arguments have different distribution target sizes.
I379 Alignment of $ is too complex
The alignment specification of the array is too complex for interprocedural analysis to verify or propagate; the
program will work correctly, but without the benefit of IPA.
I380 Distribution format of $ is too complex
The distribution format specification of the array is too complex for interprocedural analysis to verify or
propagate; the program will work correctly, but without the benefit of IPA.
I381 Distribution target of $ is too complex
The distribution target specification of the array is too complex for interprocedural analysis to verify or
propagate; the program will work correctly, but without the benefit of IPA.
I382 IPA: $ subprograms analyzed
Interprocedural analysis succeeded in finding and analyzing this many subprograms in the whole program.
I383 IPA: $ dummy arguments replaced by constants
Interprocedural analysis has found this many dummy arguments in the whole program that can be replaced by
constants.
I384 IPA: $ dummy arguments changed to INTENT(IN)
Interprocedural analysis has found this many dummy arguments in the whole program that are not modified
and can be declared as INTENT(IN).
W385 IPA: $ INTENT(IN) dummy arguments should be INTENT(INOUT)
Interprocedural analysis has found this many dummy arguments in the whole program that were declared as
INTENT(IN) but should be INTENT(INOUT).
I386 IPA: $ array alignments propagated
Interprocedural analysis has found this many array dummy arguments that could have the inherited array
alignment replaced by a descriptive alignment.PGI® User’s Guide
356
I387 IPA: $ array alignments verified
Interprocedural analysis has verified that the prescriptive or descriptive alignments of this many array dummy
arguments match the alignments of the actual argument.
I388 IPA: $ array distribution formats propagated
Interprocedural analysis has found this many array dummy arguments that could have the transcriptive
distribution format replaced by a descriptive format.
I389 IPA: $ array distribution formats verified
Interprocedural analysis has verified that the prescriptive or descriptive distribution formats of this many array
dummy arguments match the formats of the actual argument.
I390 IPA: $ array distribution targets propagated
Interprocedural analysis has found this many array dummy arguments that could have the transcriptive
distribution target replaced by a descriptive target.
I391 IPA: $ array distribution targets verified
Interprocedural analysis has verified that the prescriptive or descriptive distribution targets of this many array
dummy arguments match the targets of the actual argument.
I392 IPA: $ common blocks optimized
Interprocedural analysis has found this many common blocks that could be optimized.
I393 IPA: $ common blocks not optimized
Interprocedural analysis has found this many common blocks that could not be optimized, either because
the common block was not declared in the main program, or because it was declared differently in different
subprograms.
I394 IPA: $ replaced by constant value
The dummy argument was replaced by a constant as per interprocedural analysis.
I395 IPA: $ changed to INTENT(IN)
The dummy argument was changed to INTENT(IN) as per interprocedural analysis.
I396 IPA: array alignment propagated to $
The template alignment for the dummy argument was changed as per interprocedural analysis.
I397 IPA: distribution format propagated to $
The distribution format for the dummy argument was changed as per interprocedural analysis.
I398 IPA: distribution target propagated to $
The distribution target for the dummy argument was changed as per interprocedural analysis.
I399 IPA: common block $ not optimized
The given common block was not optimized by interprocedural analysis either because it was not declared in
the main program, or because it was declared differently in different subprograms.
E400 IPA: dummy argument $ is an asterisk, but actual argument
is not a label
The subprogram expects an alternate return label for this argument.Chapter 22. Messages
357
E401 Actual argument $ is a subprogram, but Dummy argument $ is
not declared EXTERNAL
The call statement passes a function or subroutine name to a dummy argument that is a scalar variable or
array.
E402 Actual argument $ is illegal
E403 Actual argument $ and formal argument $ have different
ranks
The actual and formal array arguments differ in rank, which is allowed only if both arrays are declared with
the HPF SEQUENCE attribute.
E404 Sequential array section of $ in argument $ is not
contiguous
When passing an array section to a formal argument that has the HPF SEQUENCE attribute, the actual argument
must be a whole array with the HPF SEQUENCE attribute, or an array section of such an array where the section
is a contiguous sequence of elements.
E405 Array expression argument $ may not be passed to
sequential dummy argument $
When the dummy argument has the HPF SEQUENCE attribute, the actual argument must be a whole array with
the HPF SEQUENCE attribute or a contiguous array section of such an array, unless an INTERFACE block is
used.
E406 Actual argument $ and formal argument $ have different
character lengths
The actual and formal array character arguments have different character lengths, which is allowed only if both
character arrays are declared with the HPF SEQUENCE attribute, unless an INTERFACE block is used.
W407 Argument $ has a different character length than dummy
argument $
The character length of the actual argument is different than the length specified for the corresponding dummy
argument.
W408 Specified main program $ is not a PROGRAM
The main program specified on the command line is a subroutine, function, or block data subprogram.
W409 More than one main program in IPA directory: $ and $
There is more than one main program analyzed in the IPA directory shown. The first one found is used.
W410 No main program found; IPA analysis fails.
The main program must appear in the IPA directory for analysis to proceed.
W411 Formal argument $ is DYNAMIC but actual argument is an
expression
W412 Formal argument $ is DYNAMIC but actual argument $ is not
I413 Formal argument $ has two reaching distributions and may
be a candidate for cloningPGI® User’s Guide
358
I414 $ and $ may be aliased and one of them is assigned
Interprocedural analysis has determined that two formal arguments because the same variable is passed in
both argument positions, or one formal argument and a global or COMMON variable may be aliased, because
the global or COMMON variable is passed as an actual argument. If either alias is assigned in the subroutine,
unexpected results may occur; this message alerts the user that this situation is disallowed by the Fortran
standard.
F415 IPA fails: incorrect IPA file
Interprocedural analysis saves its information in special IPA files in the specified IPA directory. One of these
files has been renamed or corrupted. This can arise when there are two files with the same prefix, such as
’a.hpf’ and ’a.f90’.
E416 Argument $ has the SEQUENCE attribute, but the dummy
parameter $ does not
When an actual argument is an array with the SEQUENCE attribute, the dummy parameter must have the
SEQUENCE attribute or an INTERFACE block must be used.
E417 Interface block for $ is a SUBROUTINE but should be a
FUNCTION
E418 Interface block for $ is a FUNCTION but should be a
SUBROUTINE
E419 Interface block for $ is a FUNCTION has wrong result type
W420 Earlier $ directive overrides $ directive
W421 $ directive can only appear in a function or subroutine
E422 Nonconstant DIM= argument is not supported
E423 Constant DIM= argument is out of range
E424 Equivalence using substring or vector triplets is not
allowed
E425 A record is not allowed in this context
E426 WORD type cannot be converted
E427 Interface block for $ has wrong number of arguments
E428 Interface block for $ should have $
E429 Interface block for $ should not have $
E430 Interface block for $ has wrong $
W431 Program is too large for Interprocedural Analysis to
complete
W432 Illegal type conversion $
E433 Subprogram $ called within INDEPENDENT loop not LOCAL
W434 Incorrect home array specification ignoredChapter 22. Messages
359
S435 Array declared with zero size
An array was declared with a zero or negative dimension bound, as ’real a(-1)’, or an upper bound less than
the lower bound, as ’real a(4:2)’.
W436 Independent loop not parallelized$
W437 Type $ will be mapped to $
Where DOUBLE PRECISION is not supported, it is mapped to REAL, and similarly for COMPLEX(16) or
COMPLEX*32.
E438 $ $ not supported on this platform
This construct is not supported by the compiler for this target.
S439 An internal subprogram cannot be passed as argument - $
S440 Defined assignment statements may not appear in WHERE
statement or WHERE block
S441 $ may not appear in a FORALL block
E442 Adjustable-length character type not supported on this
host - $ $
S443 EQUIVALENCE of derived types not supported on this host -
$
S444 Derived type in EQUIVALENCE statement must have SEQUENCE
attribute - $
A variable or array with derived type appears in an EQUIVALENCE statement. The derived type must have the
SEQUENCE attribute, but does not.
E445 Array bounds must be integer $ $
The expressions in the array bounds must be integer.
S446 Argument number $ to $: rank mismatch
The number of dimensions in the array or array expression does not match the number of dimensions in the
dummy argument.
S447 Argument number $ to $ must be a subroutine or function
name
S448 Argument number $ to $ must be a subroutine name
S449 Argument number $ to $ must be a function name
S450 Argument number $ to $: kind mismatch
S451 Arrays of derived type with a distributed member are not
supported
S452 Assumed length character, $, is not a dummy argument
S453 Derived type variable with pointer member not allowed in
IO - $ $PGI® User’s Guide
360
S454 Subprogram $ is not a module procedure
Only names of module procedures declared in this module or accessed through USE association can appear in
a MODULE PROCEDURE statement.
S455 A derived type array section cannot appear with a member
array section - $
A reference like A(:)%B(:), where ’A’ is a derived type array and ’B’ is a member array, is not allowed; a
section subscript may appear after ’A’ or after ’B’, but not both.
S456 Unimplemented for data type for MATMUL
S457 Illegal expression in initialization
S458 Argument to NULL() must be a pointer
S459 Target of NULL() assignment must be a pointer
S460 ELEMENTAL procedures cannot be RECURSIVE
S461 Dummy arguements of ELEMENATAL procedures must be scalar
S462 Arguments and return values of ELEMENATAL procedures
cannot have the POINTER attribute
S463 Arguments of ELEMENATAL procedures cannot be procedures
S464 An ELEMENTAL procedure cannot be passed as argument - $
Fortran Runtime Error Messages
This section presents the error messages generated by the runtime system. The runtime system displays error
messages on standard output.
Message Format
The messages are numbered but have no severity indicators because they all terminate program execution.
Message List
Here are the runtime error messages:
201 illegal value for specifier
An improper specifier value has been passed to an I/O runtime routine. Example: within an OPEN statement,
form='unknown'.
202 conflicting specifiers
Conflicting specifiers have been passed to an I/O runtime routine. Example: within an OPEN statement,
form='unformatted', blank='null'.
203 record length must be specified
A recl specifier required for an I/O runtime routine has not been passed. Example: within an OPEN statement,
access='direct' has been passed, but the record length has not been specified (recl=specifier).Chapter 22. Messages
361
204 illegal use of a readonly file
Self explanatory. Check file and directory modes for readonly status.
205 'SCRATCH' and 'SAVE'/'KEEP' both specified
In an OPEN statement, a file disposition conflict has occurred. Example: within an OPEN statement,
status='scratch' and dispose='keep' have been passed.
206 attempt to open a named file as 'SCRATCH'
207 file is already connected to another unit
208 'NEW' specified for file that already exists
209 'OLD' specified for file that does not exist
210 dynamic memory allocation failed
Memory allocation operations occur only in conjunction with namelist I/O. The most probable cause of fixed
buffer overflow is exceeding the maximum number of simultaneously open file units.
211 invalid file name
212 invalid unit number
A file unit number less than or equal to zero has been specified.
215 formatted/unformatted file conflict
Formatted/unformatted file operation conflict.
217 attempt to read past end of file
219 attempt to read/write past end of record
For direct access, the record to be read/written exceeds the specified record length.
220 write after last internal record
221 syntax error in format string
A runtime encoded format contains a lexical or syntax error.
222 unbalanced parentheses in format string
223 illegal P or T edit descriptor - value missing
224 illegal Hollerith or character string in format
An unknown token type has been found in a format encoded at run-time.
225 lexical error -- unknown token type
226 unrecognized edit descriptor letter in format
An unexpected Fortran edit descriptor (FED) was found in a runtime format item.
228 end of file reached without finding group
229 end of file reached while processing group
230 scale factor out of range -128 to 127
Fortran P edit descriptor scale factor not within range of -128 to 127.
231 error on data conversionPGI® User’s Guide
362
233 too many constants to initialize group item
234 invalid edit descriptor
An invalid edit descriptor has been found in a format statement.
235 edit descriptor does not match item type
Data types specified by I/O list item and corresponding edit descriptor conflict.
236 formatted record longer than 2000 characters
237 quad precision type unsupported
238 tab value out of range
A tab value of less than one has been specified.
239 entity name is not member of group
242 illegal operation on direct access file
243 format parentheses nesting depth too great
244 syntax error - entity name expected
245 syntax error within group definition
246 infinite format scan for edit descriptor
248 illegal subscript or substring specification
249 error in format - illegal E, F, G or D descriptor
250 error in format - number missing after '.', '-', or '+'
251 illegal character in format string
252 operation attempted after end of file
253 attempt to read non-existent record (direct access)
254 illegal repeat count in format363
Index
Symbols
64-Bit Programming, 125
A
Arguments
passing, 113
passing by value, 113
Arrays
indices, 114
Auto-parallelization, 32
B
Basic block, 22
Blocks
Fortran named common, 112
Bounds checking, 239
C
C/C++ Builtin Functions, 75
C/C++ Math Header File, 75
C$PRAGMA C, 72
C++ Name Mangling, 159
C++ Standard Template Library, 88
Cache tiling
failed cache tiling, 241
with -Mvect, 237
Command line
case sensitivity, 2
include files, 5
option order, 3
Command-line Options, 3, 15, 163,
184
-#, 170, 170
-###, 171, 171
-A, 208
-a, 208
-alias, 209
-B, 209
-b, 210
-b3, 210
--Bdynamic, 171, 171
Build-related, 163
-byteswapio, 172
-C, 172
-c, 173
--cfront_2.1, 211
--cfront_3.0, 211
--compress_names, 212
--create_pch, 212
-d, 173
-D, 174
Debug-related, 166, 167, 167
--diag_error, 212
--diag_remark, 212
--diag_suppress, 213
--diag_warning, 213
--display_error_number, 213,
214, 214
-dryrun, 174
-E, 175
-F, 175
-fast, 175
-fastsse, 176
-flagcheck, 176
-flags, 176
-fpic, 176, 177
-fPIC, 177
-G, 177
-g, 177
-g77libs, 178
Generic PGI options, 170
-gopt, 178
-help, 178
-I, 180
-i2, -i4 and -i8, 181
--keeplnk, 183
-Kflag, 181
-L, 183
-l, 183
-M, 214
-Mallocatable, 226
-Manno, 239, 242
-Masmkeyword, 224
-Mbackslash, 226
-Mbounds, 239
-Mbyteswapio, 239
-Mcache_align, 230
-Mchkfpstk, 239
-Mchkptr, 239
-Mchkstk, 239
-mcmodel=medium, 126
-mcmodel=small, 126
-Mconcur, 230
-Mcpp, 240
-Mcray, 231
-MD, 215
-Mdaz, 220
-Mdclchk, 226
-Mdefaultunit, 227
-Mdepchk, 231
-Mdlines, 227
-Mdll, 240
-Mdollar, 224, 227
-Mdse, 231
-Mdwarf1, 220
-Mdwarf2, 220
-Mdwarf3, 220
-Mextend, 227
-Mextract, 228
-Mfcon, 224
-Mfixed, 227
-Mflushz, 220
-Mfprelaxed, 232
-Mfree, 227
-Mfunc32, 221
-Mgccbugs, 240
-Mi4, 232
-Minform, 241
-Minline, 229
-Miomutex, 227
-Mipa, 232
-Mkeepasm, 242
-Mlarge_arrays, 126, 126, 221
-Mlfs, 225
-Mlist, 242PGI® User’s Guide
364
-Mloop32, 234
-Mlre, 234
-Mmakedll, 242, 242
-Mneginfo, 241
-Mnoasmkeyword, 224
-Mnobackslash, 226
-Mnobounds, 239
-Mnodaz, 220
-Mnodclchk, 227
-Mnodefaultunit, 227
-Mnodepchk, 231
-Mnodlines, 227
-Mnodse, 231
-Mnoflushz, 220
-Mnofprelaxed, 232
-Mnoframe, 234
-Mnoi4, 234
-Mnoiomutex, 227
-Mnolarge_arrays, 221, 221
-Mnolist, 242
-Mnoloop32, 234
-Mnolre, 234
-Mnomain, 221
-Mnoonetrip, 227
-Mnoopenmp, 242
-Mnopgdllmain, 242
-Mnoprefetch, 235
-Mnor8, 235
-Mnor8intrinsics, 236
-Mnorecursive, 222
-Mnoreentrant, 223
-Mnoref_externals, 222
-Mnosave, 227
-Mnoscalarsse, 236
-Mnosecond_underscore, 223
-Mnosgimp, 242
-Mnosignextend, 223
-Mnosingle, 225
-Mnosmart, 236
-Mnostartup, 225, 225
-Mnostddef, 226
-Mnostdlib, 226, 226
-Mnostride0, 223
-Mnounixlogical, 228
-Mnounroll, 237
-Mnoupcase, 228, 228
-Mnovect, 238
-Mnovintr, 238
-module, 191
-Monetrip, 227
-mp, 191
-Mpfi, 235
-Mpfo, 235
-Mprefetch, 235
-Mpreprocess, 242
-Mprof, 222
-Mr8, 235
-Mr8intrinsics, 236
-Mrecursive, 222
-Mreentrant, 222
-Mref_externals, 222
-Msafe_lastval, 223
-Msafeptr, 236
-Msave, 227
-Mscalarsse, 236
-Mschar, 224
-Msecond_underscore, 223
-Msignextend, 223
-Msingle, 225
-Msmart, 236
-Mstandard, 227
-Mstride0, 223
-Muchar, 225
-Munix, 223
-Munixlogical, 227
-Munroll, 237
-Mupcase, 228
-Mvarargs, 223
-Mvect, 237
-nfast, 192
--llalign, 214, 221, 231, 231, 235,
236
--alternative_tokens, 209, 209,
210, 214, 217, 218, 219
-nontemporal moves, 221
-noswitcherror, 192
-O, 193
-o, 194
--
optk_allow_dollar_in_id_chars,
215
-P, 215
-pc, 194
--pch, 216, 216, 219
--pch_dir, 216
-pg, 196, 196, 197
--preinclude, 217
-Q, 197
-R, 198
-r, 198, 198
-r4 and -r8, 198
-rc, 199
-rpath, 199
-s, 184, 199
-S, 200
-shared, 200
-show, 200
-silent, 201
-soname, 201
-stack, 201
syntax, 2
-t, 218
-time, 202
-tp, 202
-u, 205
-U, 205
--use_pch, 217
-V, 205
-v, 206
-W, 206
-w, 207
-Xs, 207
-Xt, 208
Compilation driver, 1
Compilers
Invoke at command level, 1
PGC++, xxvi
PGF77, xxvi
PGF95, xxvi
PGHPF, xxvi
Constraints
*, 144, 144
&, 144
%, 144
+, 144
=, 144
character, 139
machine, 141Index
365
machine, example, 142
modifiers, 143
multiple alternative, 143
operand, 139
operant aliases, 145
simple, 139
cpp, 5
D
Data Types, 6, 151
Aggregate, 6
attributes, 158
bit-fields, 158
C/C++ aggregate alignment, 157
C/C++ scalar data types, 154
C/C++ struct, 156
C/C++ void, 158
C++ class and object layout, 156
C++ classes, 156
DEC structures, 153
DEC Unions, 153
F90 derived types, 154
Fortran Scalars, 151
internal padding, 157
scalars, 6
tail padding, 157
Deployment, 103
Directives
C/C++, 3, 3
Fortran, 3
optimization, 63, 263
Parallelization, 51, 243, 263
prefetch, 69
scope, 66
E
Environment variables, 89, 89, 91,
92
FLEXLM_BATCH, 91, 93
FORTRAN_OPT, 93
GMON_OUT_PREFIX, 93
LD_LIBRARY_PATH, 91
MANPATH, 93, 93, 94
MP_BIND, 94
MP_BLIST, 95
MP_SPIN, 95
MP_WARN, 95
NCPUS, 96
NCPUS_MAX, 96
NO_STOP_MESSAGE, 96
OMP_STACK_SIZE, 9, 11, 12, 59,
60, 92
OMP_WAIT_POLICY, 59, 60, 92
PATH, 92, 96
PGI, 96
PGI_CONTINUE, 97
PGI_OBJSUFFIX, 97
PGI_TERM, 97
PGI_TERM_DEBUG, 97, 99, 240
PWD, 99
STATIC_RANDOM_SEED, 99
TMPDIR, 100, 100
F
Filename Conventions, 3
extensions, 3
Input Files, 3
Output Files, 5
Floating-point stack, 194
Fortran
directive summary, 64
named common blocks, 112
Fortran Parallelization Directives
ATOMIC, 251
DOACROSS, 246, 246
Function Inlining
inlining and makefiles, 48
inlining examples, 49
inlining restrictions, 49
H
Hello example, 2
I
Inline Assembly
clobber list, 138
Inter-language Calling, 109
%VAL, 113
arguments and return values, 113
array indices, 114
C$PRAGMA C, 72
C++ calling C, 116
C++ calling Fortran, 119
C calling C++, 117
character case conventions, 111
character return values, 113
compatible data types, 111
Fortran calling C, 115
Fortran calling C++, 118
underscores, 72, 111
L
Language options, 223
Libraries
-Bdynamic option, 171, 171
BLAS, 88
FFTs, 88
LAPACK, 88
LIB3F, 88
shared object files, 76
Linux, 9
Header Files, 9
large static data, 126
Parallelization, 9
Listing Files, 239, 242, 242
Loops
failed auto-parallelization, 34
innermost, 34
scalars, 34
timing, 34
Loop unrolling, 27
M
MAC OS
Parallelization, 12
MAC OS X
Header Files, 11
Mangling
C++ names, 159
types, 160
Modifiers
assembly string, 145
characters, 145
N
Name mangling
local class, 161
nested class, 161PGI® User’s Guide
366
template class, 161
type, 160
O
OpenMP C/C++ Pragmas, 51, 243
flush, 249, 250
ordered, 251
parallel, 251
parallel sections, 255, 256
OpenMP C/C++ Support Routines
omp_destroy_lock(), 58
omp_destroy_nest_lock(), 58
omp_get_dynamic(), 57
omp_get_max_threads(), 56
omp_get_nested(), 57
omp_get_num_procs(), 56
omp_get_num_threads(), 55, 55
omp_get_stack_size(), 56
omp_get _thread_num(), 55
omp_get_wtick(), 58
omp_get_wtime(), 57
omp_in_parallel(), 56
omp_init_lock(), 58
omp_init_nest_lock(), 58
omp_set_dynamic(), 57
omp_set_lock(), 58
omp_set_nest_lock(), 58
omp_set_nested(), 57
omp_set_num_threads(), 55
omp_set_stack_size(), 56
omp_test_lock(), 58
omp_test_nest_lock(), 58
omp_unset_lock(), 58
omp_unset_nest_lock(), 58
OpenMP C++ Pragmas
omp critical, 245
OpenMP environment variables
MPSTKZ, 91, 94
OMP_DYNAMIC, 59, 59, 59, 60,
92, 92
OMP_NESTED, 59, 59, 92
OMP_NUM_THREADS, 59, 59, 92
OpenMP Fortran Directives, 51, 243,
263
ATOMIC, 244
BARRIER, 244
CRITICAL, 245
DO, 247
FLUSH, 249
MASTER, 250
ORDERED, 251
PARALLEL, 251
PARALLEL DO, 254, 254
PARALLEL SECTIONS, 255
PARALLEL WORKSHARE, 256
SECTIONS, 257, 257
SINGLE, 257
THREADPRIVATE, 258
WORKSHARE, 259
OpenMP Fortran Support Routines
omp_destroy_lock(), 58
omp_get_dynamic(), 57
omp_get_max_threads(), 56
omp_get_nested(), 57
omp_get_num_procs(), 56
omp_get_num_threads(), 55, 55
omp_get_stack_size(), 56
omp_get_thread_num(), 55
omp_get_wtick(), 58
omp_get_wtime(), 57
omp_in_parallel(), 56
omp_init_lock(), 58
omp_set_dynamic(), 57
omp_set_lock(), 58
omp_set_nested(), 57
omp_set_num_threads(), 55
omp_set_stack_size(), 56
omp_test_lock(), 58
omp_unset_lock(), 58
Operand
aliases, 145
modifier *, 144, 144
modifier &, 144
modifier %, 144
modifier +, 144
modifier =, 144
Operand constaints
see constraints, 139
Operand constraints
machine, 141
Optimization, 63, 263
C/C++ pragmas, 42, 64
C/C++ pragmas scope, 67
cache tiling, 237
Fortran directives, 42, 63, 263
Fortran directives scope, 66
function inlining, 14, 22, 45
global, 25
global optimization, 22, 25
inline libraries, 46
Inter-Procedural Analysis, 22
IPA, 22
local, 25
local optimization, 22
loop optimization, 22
loops, 234, 234, 234
loop unrolling, 22, 27
no level specified, 25
none, 25
-O, 193
-O0, 24
-O1, 24
-O2, 24
-O3, 25, 25
-Olevel, 24
parallelization, 22, 32
PFO, 22
pointers, 236
prefetching, 235, 235, 235
profile-feedback (PFO), 41
Profile-Feedback Optimization, 22
vectorization, 22, 28
Options
Mchkfpstk, 97
P
Parallelization, 32
auto-parallelization, 32
failed auto-parallelization, 34,
241
Mac OS, 12
-Mconcur auto-parallelization,
230
NCPUS environment variable, 33
safe_lastval, 35
user-directed, 191
Parallelization Directives, 51, 243,
263Index
367
Parallelization Pragmas, 51, 243
Pragmas
C/C++, 3
optimization, 64
scope, 67
Prefetch directives, 69
Preprocessor
cpp, 5
Fortran, 5
Proprietary environment variables
FORTRAN_OPT, 91, 93
GMON_OUT_PREFIX, 91, 91
MANPATH, 91
MP_BIND, 91
MP_BLIST, 91
MP_SPIN, 91
MP_WARN, 91
NCPUS, 91
NCPUS_MAX, 91
NO_STOP_MESSAGE, 92
PGI, 92
PGI_CONTINUE, 92
PGI_OBJSUFFIX, 92
PGI_STACK_USAGE, 92
PGI_TERM, 92
PGI_TERM_DEBUG, 92, 92
STATIC_RANDOM_SEED, 92
TMP, 92
TMPDIR, 92
R
Return values
character, 113
Run-time Environment, 271
S
Shared object files, 76
SUA/SFU, 11
Header Files, 11
Parallelization, 11
T
Timing
CPU_CLOCK, 43
execution, 43
SYSTEM_CLOCK, 43
Tools
PGDBG, xxvi
PGPROF, xxvi, xxvi
V
Vectorization, 28, 237
SSE instructions, 238
W
Win32 Calling Conventions
C, 120, 121
Default, 120, 121
STDCALL, 120, 121
symbol name construction, 121
UNIX-style, 120, 122368
About This Guide
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Scienti?c Libraries User’s Guide
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Scienti?c Libraries User’s Guide 004–2151–002
This guide has been expanded to include appendixes that describe the implementation of version 2 of the
Math library (libm), used on UNICOS systems, as well as describing the algorithms used in that library.Record of Revision
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2.0 July 1996.
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004–2151–002 iContents
Page
About This Guide xi
Related publications . . . . . . . . . . . . . . . . . . . . . . . xi
Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . xiv
Obtaining Publications . . . . . . . . . . . . . . . . . . . . . . . xv
Reader Comments . . . . . . . . . . . . . . . . . . . . . . . . xv
Introduction [1] 1
Parallel Processing Issues [2] 3
Parallel Processing Overview . . . . . . . . . . . . . . . . . . . . . 3
Parallel Processing: Hardware Level . . . . . . . . . . . . . . . . . . 3
Parallel Processing: Operating System Level . . . . . . . . . . . . . . . 4
Parallel Processing: Code Level . . . . . . . . . . . . . . . . . . . 5
Costs and Bene?ts of Parallel Processing . . . . . . . . . . . . . . . . . 5
Bene?ts of Parallel Processing . . . . . . . . . . . . . . . . . . . . 6
Parallel Processing Overhead . . . . . . . . . . . . . . . . . . . . 6
Parallelism and Vectorization . . . . . . . . . . . . . . . . . . . . 7
Parallelism and Load Balancing . . . . . . . . . . . . . . . . . . . 8
Performance Issues . . . . . . . . . . . . . . . . . . . . . . . . 8
Calculating Speedups in Multitasked Programs . . . . . . . . . . . . . . 8
Amdahl’s Law . . . . . . . . . . . . . . . . . . . . . . . 9
Determining Ef?ciency . . . . . . . . . . . . . . . . . . . . . . 10
Estimating Percentage of Parallelism . . . . . . . . . . . . . . . . . . 11
Parallel Processing Environments . . . . . . . . . . . . . . . . . . . 11
Environment Variables . . . . . . . . . . . . . . . . . . . . . . 12
004–2151–002 iiiScienti?c Libraries User’s Guide
Page
The Dedicated Environment . . . . . . . . . . . . . . . . . . . . 13
The Multiuser Environment . . . . . . . . . . . . . . . . . . . . 13
Measuring Scienti?c Library Performance . . . . . . . . . . . . . . . . . 14
Simple Measurements . . . . . . . . . . . . . . . . . . . . . . 14
Determining Multitasking of Routines . . . . . . . . . . . . . . . . . 15
Parallel Processing Strategies . . . . . . . . . . . . . . . . . . . . . 20
Problem Sizes . . . . . . . . . . . . . . . . . . . . . . . . . 20
Strategies for a Dedicated Environment . . . . . . . . . . . . . . . . . 21
Strategies for a Multiuser Environment . . . . . . . . . . . . . . . . . 21
LAPACK [3] 25
LAPACK in the Scienti?c Library . . . . . . . . . . . . . . . . . . . 25
Types of Problems Solved by LAPACK . . . . . . . . . . . . . . . . . . 26
Solving Linear Systems . . . . . . . . . . . . . . . . . . . . . . 27
Factoring a Matrix . . . . . . . . . . . . . . . . . . . . . . . 29
Example 1: LU factorization . . . . . . . . . . . . . . . . . . . 30
Example 2: Symmetric inde?nite matrix factorization . . . . . . . . . . . 31
Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 33
Example 3: Error conditions . . . . . . . . . . . . . . . . . . . 33
Solving from the Factored Form . . . . . . . . . . . . . . . . . . . . 34
Condition Estimation . . . . . . . . . . . . . . . . . . . . . . 36
Example 4: Roundoff errors . . . . . . . . . . . . . . . . . . . 37
Use in Error Bounds . . . . . . . . . . . . . . . . . . . . . . 37
Equilibration . . . . . . . . . . . . . . . . . . . . . . . . . 39
Iterative Re?nement . . . . . . . . . . . . . . . . . . . . . . . 41
Example 5: Hilbert matrix . . . . . . . . . . . . . . . . . . . 41
Error Bounds . . . . . . . . . . . . . . . . . . . . . . . . 43
Inverting a Matrix . . . . . . . . . . . . . . . . . . . . . . . 44
Solving Least Squares Problems . . . . . . . . . . . . . . . . . . . . 45
iv 004–2151–002Contents
Page
Orthogonal Factorizations . . . . . . . . . . . . . . . . . . . . . 45
Example 6: Orthogonal factorization . . . . . . . . . . . . . . . . 46
Multiplying by the Orthogonal Matrix . . . . . . . . . . . . . . . . . 48
Generating the Orthogonal Matrix . . . . . . . . . . . . . . . . . . 49
Comparing Answers . . . . . . . . . . . . . . . . . . . . . . . 50
Using Sparse Linear Solvers [4] 53
Sparse Matrices . . . . . . . . . . . . . . . . . . . . . . . . . 53
Solution Techniques . . . . . . . . . . . . . . . . . . . . . . . 54
Direct Methods . . . . . . . . . . . . . . . . . . . . . . . . 55
Iterative Methods . . . . . . . . . . . . . . . . . . . . . . . 56
Sparse Solvers . . . . . . . . . . . . . . . . . . . . . . . . . 57
Data Structures for General Sparse Matrices . . . . . . . . . . . . . . . 57
Direct Solvers . . . . . . . . . . . . . . . . . . . . . . . . . 58
Iterative Solvers . . . . . . . . . . . . . . . . . . . . . . . . 59
Other Solvers . . . . . . . . . . . . . . . . . . . . . . . . . 60
Choosing a Solver . . . . . . . . . . . . . . . . . . . . . . . . 62
Using Sparse Solvers . . . . . . . . . . . . . . . . . . . . . . 62
Tridiagonal Systems . . . . . . . . . . . . . . . . . . . . . . . 62
General-patterned Sparse Linear Systems . . . . . . . . . . . . . . . . 63
Choosing a Method Based on Problem Type . . . . . . . . . . . . . . . 64
Iterative Methods . . . . . . . . . . . . . . . . . . . . . . . 65
Preconditioning . . . . . . . . . . . . . . . . . . . . . . . 65
Direct General Sparse Solvers . . . . . . . . . . . . . . . . . . . . 67
Performance Tuning . . . . . . . . . . . . . . . . . . . . . . . 67
Parallel Processing . . . . . . . . . . . . . . . . . . . . . . . 67
Reusing Information . . . . . . . . . . . . . . . . . . . . . . 68
Reuse of Structure . . . . . . . . . . . . . . . . . . . . . . 68
Multiple Right-hand Sides . . . . . . . . . . . . . . . . . . . . 68
004–2151–002 vScienti?c Libraries User’s Guide
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Reuse of Values . . . . . . . . . . . . . . . . . . . . . . . 68
Save/restart . . . . . . . . . . . . . . . . . . . . . . . . 69
SITRSOL Tuning Issues . . . . . . . . . . . . . . . . . . . . . 69
Direct Solver Tuning Issues . . . . . . . . . . . . . . . . . . . . 70
SITRSOL Quick Reference . . . . . . . . . . . . . . . . . . . . . 72
Usage Examples . . . . . . . . . . . . . . . . . . . . . . . . . 75
Example 7: General symmetric positive de?nite . . . . . . . . . . . . . . 75
Example 8: General unsymmetric . . . . . . . . . . . . . . . . . . 79
Example 9: Reuse of structure . . . . . . . . . . . . . . . . . . . 84
Example 10: Multiple right-hand sides . . . . . . . . . . . . . . . . 89
Example 11: Save/restart . . . . . . . . . . . . . . . . . . . . 93
Out-of-core Linear Algebra Software [5] 101
Out-of-core Routines . . . . . . . . . . . . . . . . . . . . . . . 101
Virtual Matrices . . . . . . . . . . . . . . . . . . . . . . . . . 102
Unit Numbers . . . . . . . . . . . . . . . . . . . . . . . . 102
File Format . . . . . . . . . . . . . . . . . . . . . . . . . 103
Leading Virtual Dimension . . . . . . . . . . . . . . . . . . . . 104
De?nition and Rede?nition of Elements . . . . . . . . . . . . . . . . 104
File Size . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Packed Storage Mode . . . . . . . . . . . . . . . . . . . . . . 105
Page Size . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Subroutine Types . . . . . . . . . . . . . . . . . . . . . . . . 106
Complex Routines . . . . . . . . . . . . . . . . . . . . . . . 106
Summary of Routines . . . . . . . . . . . . . . . . . . . . . . 107
Initialization and Termination Subroutines . . . . . . . . . . . . . . . . 109
Virtual Copy Subroutines . . . . . . . . . . . . . . . . . . . . . 109
Virtual LAPACK Subroutines . . . . . . . . . . . . . . . . . . . . 110
Virtual BLAS Subroutines . . . . . . . . . . . . . . . . . . . . . 111
vi 004–2151–002Contents
Page
Using Strassen’s algorithm . . . . . . . . . . . . . . . . . . . . 111
Lower-level Routines . . . . . . . . . . . . . . . . . . . . . . 112
Examples of Out-of-core Subroutine Use . . . . . . . . . . . . . . . . . 113
Example 12: Creating a virtual matrix . . . . . . . . . . . . . . . . . 113
Example 13: Multiplying a virtual matrix . . . . . . . . . . . . . . . 113
Example 14: Example of protocol usage . . . . . . . . . . . . . . . . 114
UNICOS Environment Variables . . . . . . . . . . . . . . . . . . . . 115
Multitasking . . . . . . . . . . . . . . . . . . . . . . . . . 116
Error Reporting . . . . . . . . . . . . . . . . . . . . . . . . . 116
Performance Measurement and Tuning . . . . . . . . . . . . . . . . . . 117
Page-Buffer Space . . . . . . . . . . . . . . . . . . . . . . . 118
Memory Usage Guidelines . . . . . . . . . . . . . . . . . . . . . 118
Memory Requirement for VSGETRF and VCGETRF Routines . . . . . . . . . . 119
Sample Performance Statistics . . . . . . . . . . . . . . . . . . . . 119
Appendix A Appendix A: libm Version 2 123
Overview of Math Libraries . . . . . . . . . . . . . . . . . . . . . 123
The 1 ULP Criterion . . . . . . . . . . . . . . . . . . . . . . . 124
Numerical Methods . . . . . . . . . . . . . . . . . . . . . . . 125
Side Effects . . . . . . . . . . . . . . . . . . . . . . . . . 128
Appendix B Appendix B: Math Algorithms 129
Single-precision Real Logarithm Functions ln(x) and log(x) . . . . . . . . . . . 129
Procedure 1: ln(x) and log(x) . . . . . . . . . . . . . . . . . . . 129
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Single-precision Real Logarithm Functions ALOG(x) and ALOG10(x) . . . . . . . . . 132
Procedure 2: ALOG(x) and ALOG10(x) . . . . . . . . . . . . . . . . . 132
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Single-precision Real ASIN(x) and ACOS(x) Functions . . . . . . . . . . . . . 135
004–2151–002 viiScienti?c Libraries User’s Guide
Page
Procedure 3: ASIN(x) . . . . . . . . . . . . . . . . . . . . . . 135
Procedure 4: ACOS(x) . . . . . . . . . . . . . . . . . . . . . . 136
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Single-precision Real ATAN(x) Function . . . . . . . . . . . . . . . . . . 138
Procedure 5: ATAN(x) . . . . . . . . . . . . . . . . . . . . . . 138
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Single-precision ATAN(y,x) Function . . . . . . . . . . . . . . . . . . . 139
Procedure 6: ATAN(y,x) . . . . . . . . . . . . . . . . . . . . . 139
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Single-precision Real CBRT(x) Function . . . . . . . . . . . . . . . . . . 143
Procedure 7: CBRT(x) . . . . . . . . . . . . . . . . . . . . . . 143
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Single-precision Real Exponential Function E
x
. . . . . . . . . . . . . . . 145
Procedure 8: e
x
. . . . . . . . . . . . . . . . . . . . . . . . 145
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Single-precision Real Power Function x
y
. . . . . . . . . . . . . . . . . 147
Procedure 9: x
y
. . . . . . . . . . . . . . . . . . . . . . . . 147
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Single-precision Real SIN(x) and COS(x) Functions . . . . . . . . . . . . . . 151
Procedure 10: SIN(x) and COS(x) . . . . . . . . . . . . . . . . . . 151
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Single-precision Real COSH(x) and SINH(x) Functions . . . . . . . . . . . . . 155
Procedure 11: COSH(x) and SINH(x) . . . . . . . . . . . . . . . . . 155
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Single-precision Real SQRT(x) Function . . . . . . . . . . . . . . . . . . 156
Procedure 12: SQRT(x) . . . . . . . . . . . . . . . . . . . . . 156
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Single-precision TAN(x) and COT(x) Functions . . . . . . . . . . . . . . . . 158
viii 004–2151–002Contents
Page
Procedure 13: TAN(x) and COT(x) . . . . . . . . . . . . . . . . . . 158
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Single-precision Real TANH(x) Function . . . . . . . . . . . . . . . . . . 162
Procedure 14: TANH(x) . . . . . . . . . . . . . . . . . . . . . 162
Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Glossary 165
Index 171
Figures
Figure 1. Pipelining in add operation . . . . . . . . . . . . . . . . . . 4
Figure 2. Pipelining and chaining . . . . . . . . . . . . . . . . . . . 4
Figure 3. Cost/robustness: general symmetric sparse solvers . . . . . . . . . . 63
Figure 4. Cost/robustness: general unsymmetric sparse solvers . . . . . . . . . 64
Figure 5. In-memory to virtual matrix copy . . . . . . . . . . . . . . . . 110
Figure 6. Layered software design . . . . . . . . . . . . . . . . . . . 112
Tables
Table 1. Relative cost for SGER . . . . . . . . . . . . . . . . . . . . 23
Table 2. Factorization forms . . . . . . . . . . . . . . . . . . . . 30
Table 3. Solves times: LAPACK and solver routines . . . . . . . . . . . . . 35
Table 4. Veri?cation tests for LAPACK (all should be O(1)) . . . . . . . . . . . 50
Table 5. Summary of tridiagonal solvers . . . . . . . . . . . . . . . . 61
Table 6. SITRSOL argument summary . . . . . . . . . . . . . . . . . 72
Table 7. iparam summary . . . . . . . . . . . . . . . . . . . . . 73
Table 8. rparam summary . . . . . . . . . . . . . . . . . . . . . 74
Table 9. Summary of out-of-core routines for linear algebra . . . . . . . . . . . 107
004–2151–002 ixAbout This Guide
This publication describes the Scienti?c Libraries (libsci) which run on
UNICOS systems. The information in this manual supplements the man pages
provided with the Scienti?c Library.
This document is a user’s guide for programmers. Readers should have a
working knowledge of the UNICOS operating system, have an understanding
of the Fortran programming language, and have a working familiarity with
scienti?c and mathematical theories.
Related publications
The following publications provide information related to the Scienti?c Library:
• UNICOS User Commands Reference Manual
• UNICOS System Libraries Reference Manual
• Scienti?c Library Reference Manual
• Optimizing Application Code on UNICOS Systems
• CF90 Commands and Directives Reference Manual
• Fortran Language Reference Manual, Volume 1
• Fortran Language Reference Manual, Volume 2
• Fortran Language Reference Manual, Volume 3
• LINPACK User’s Guide
• LAPACK User’s Guide
The following publications provide detailed information about the topics
discussed in this manual. In many cases, these documents are referenced
speci?cally in this manual.
• Anderson, E., Z. Bai, C. Bischof, J. Demmel, J. Dongarra, J. Du Croz, A.
Greenbaum, S. Hammarling, A. McKenney, S. Ostrouchov, and D. Sorensen.
LAPACK User’s Guide. Philadelphia SIAM, 1992.
004–2151–002 xiScienti?c Libraries User’s Guide
• Anderson, Edward, Jack Dongarra, and Susan Ostrouchov. Installation guide
for LAPACK. LAPACK Working Note 41, Technical Report CS-91-138.
University of Tennessee (Feb. 1992).
• Argham, Nicolas J. Accuracy and Stability of Numeric Algorithms. Philadelphia
SIAM, 1996.
• Arioli, M., J. W. Demmel, and I. S. Duff. Solving sparse linear systems with
sparse backward error. SIAM J. Matrix Anal. Appl. 10 (1989).
• Ashcraft, Cleve. A vector implementation of the multifrontal method for
large sparse, symmetric positive de?nite linear systems. Technical Report
ETA-TR-51. Boeing Computer Services, 1987.
• Duff, I. S., A. M. Erisman, and J. K. Reid. Direct Methods for Sparse Matrices.
Monographs on Numerical Analysis. New York: Oxford University Press,
1986.
• Duff, Iain, Michele Marrone, and Giuseppe Radicati. A proposal for
user-level sparse BLAS. Technical Report TR/PA/92/85. CERFACS (Dec.
1992).
• George, Alan and Joseph W-H Liu. Computer Solution of Large Sparse Positive
De?nite Systems. Prentice-Hall Series in Computational Mathematics.
Englewood Cliffs, NJ: Prentice-Hall, Inc., 1981.
• Golub, Gene and James M. Ortega. Scienti?c Computing: An Introduction with
Parallel Computing. Boston: Academic Press, 1993.
• Golub, Gene H. and Charles F. Van Loan. Matrix Computations. 2nd edition.
Baltimore, Maryland: Johns Hopkins University Press, 1989.
• Hageman, Louis A. and David M. Young. Applied Iterative Methods.
Computer Science and Applied Mathematics. New York and London:
Academic Press, 1981.
• Heroux, Michael A. A reverse communication interface for ‘‘matrix-free’’
preconditioned iterative solvers. Edited by C.A. Brebbia, D. Howard, and A.
Peters In Applications of Supercomputers in Engineering II, 207-213. Boston:
Computational Mechanics Publications, 1991.
• Heroux, Michael A. A proposal for a sparse BLAS toolkit. Technical Report
TR/PA/92/90. CERFACS (Dec. 1992).
• Heroux, Michael A., Phuong Vu, and Chao Wu Yang. A parallel
preconditioned conjugate gradient package for solving sparse linear systems
on a Cray Y-MP. Applied Numerical Mathematics, 8 (1991).
xii 004–2151–002About This Guide
• Hestenes, M. R. and E. Stiefel. Methods of conjugate gradients for solving
linear systems. J. Res. National Bureau of Standards 49 (1952): 409-436.
• Kincaid, David R., Thomas C. Oppe, John R. Respess, and David M. Young.
ITPACKV 2C User’s Guide. Technical Report CNA-191. The University of
Texas at Austin: Center for Numerical Analysis, (Nov. 1984).
• Manteuffel, T. A. An incomplete factorization technique for positive de?nite
linear systems. Math. Comp. 34 (1980): 473-497.
• Oppe, Thomas C., Wayne D. Joubert, and David R. Kincaid. NSPCG User’s
Guide. The University of Texas at Austin: Center for Numerical Analysis,
(Dec. 1988).
• Reid, J. K., editor. On the Method of Conjugate Gradients for the Solution of
Large Sparse Systems of Linear Equations. Large Sparse Sets of Linear
Equations, Academic Press, 1971.
• Saad, Youcef. SPARSKIT: a basic tool kit for sparse matrix computations.
Preliminary Version.
• Saad, Youcef. Practical use of polynomial preconditionings for the conjugate
gradient method., 6(4) (Oct. 1985): 865-881.
• Saad, Youcef and Martin H. Schultz. GMRES: A generalized minimal
residual algorithm for solving nonsymmetric linear systems. SIAM Journal of
Scienti?c and Statistical Computing, 7(3) (Jul. 1986): 856-869.
• Sonneveld, Peter. CGS, a fast lanczos-type solver for nonsymmetric linear
systems. SIAM Journal of Scienti?c and Statistical Computing, 10(1) (Jan. 1989):
36-52.
• Stewart, G. W. Introduction to Matrix Computations. Orlando, Florida:
Academic Press, 1973.
• Wilkinson, J. H. The Algebraic Eigenvalue Problem. Oxford, England: Oxford
University Press, 1965.
• Yang, Chao W. A parallel multifrontal method for sparse symmetric de?nite
linear systems on the Cray Y-MP. Proceedings of the Fifth SIAM Conference on
Parallel Processing for Scienti?c Computing. Houston, Texas (Apr. 1992).
You can ?nd a good general reference on the solution of sparse linear systems
in Golub and Van Loan. You can ?nd a good introduction to direct and iterative
methods, as well as methods for special linear systems, in these texts. See the
special section of the November 1989 issue of the SIAM Journal of Scienti?c and
Statistical Computing, pages 1135-1232 for an updated general reference.
004–2151–002 xiiiScienti?c Libraries User’s Guide
See George and Liu, Duff and Erisman, and Reid for classical references that
give a thorough and in-depth treatment of sparse direct solvers. Another
common reference is Ashcraft.
The original conjugate gradient algorithm was presented in Hestenes and
Stiefel; however, Reid presented the ?rst practical application. A classical text in
iterative methods is that of Hageman and Young. You can ?nd good
discussions of the biconjugate gradient and biconjugate gradient squared
methods in Sonneveld. GMRES is presented by Saad and Schultz.
You can ?nd some references on data structures in SPARSKIT and in the
proposals for sparse BLAS.
Three articles that deal directly with the Cray Research libsci sparse solvers are
Yang on direct solvers, Heroux (1991), and Heroux, Vu, and Yang on SITRSOL.
Conventions
The following conventions are used throughout this documentation:
command This ?xed-space font denotes literal items, such as
pathnames, man page names, commands, and
programming language structures.
variable Italic typeface denotes variable entries and words
or concepts being de?ned.
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xiv 004–2151–002About This Guide
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004–2151–002 xvScienti?c Libraries User’s Guide
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xvi 004–2151–002Introduction [1]
This manual describes the Scienti?c Libraries which run on UNICOS systems.
The information in this manual supplements the man pages provided with the
Scienti?c Library and provides details about the implementation and usage of
these library routines on UNICOS systems.
This manual includes the following sections:
• Chapter 2, page 3, discusses parallel processing environments, ways to
measure parallel processing performance, and the implementation strategies
used in the Scienti?c Library routines.
• Chapter 3, page 25, discusses dense linear algebra problems, including
systems of linear equations, linear least squares problems, eigenvalue
problems, and singular value problems.
• Chapter 4, page 53, discusses sparse matrices and solution techniques for
sparse linear systems.
• Chapter 5, page 101, discusses the out-of-core routines, virtual matrices, and
subroutines used with out-of-core routines.
• Appendix A, page 123, discusses libm Version 2, the default UNICOS math
library.
• Appendix B, page 129, discusses the algorithms used in libm.
004–2151–002 1Parallel Processing Issues [2]
Parallel processing is a method of splitting a computational task into subtasks,
and then simultaneously performing the subtasks. This section discusses the
different ways parallel processing strategies used on UNICOS systems, and
what effects those implementations have on the performance of your code.
2.1 Parallel Processing Overview
Parallel processing is performed at the hardware level, the operating system
level, and the code level. This subsection brie?y discusses these different types
of parallel processing.
2.1.1 Parallel Processing: Hardware Level
At the hardware level, parallel processing is accomplished by using the
following methods:
• parallel instruction execution, which is the execution of one instruction per
clock period, even those instructions that take several clock periods to
complete execution.
• vectorization, which is a form of parallel processing that uses instruction
segmenting and vector registers.
• I/O subsystems or foreground processors, which is the execution of operations
in parallel with processes running in the main processors that perform I/O.
• time slicing, in which the system works on several jobs or processes
simultaneously.
• pipelining, which allows each step of an operation to pass its result to the
next step after only one clock period (see Figure 1).
• chaining, which allows the movement of elements to continue from one
vector operation to another, so that a process including more than one
vector operation is executed as one long vectorized operation (see Figure 2).
004–2151–002 3Scienti?c Libraries User’s Guide
A
B
Operands
1 2 3 4 5 6 7
Clock periods
C
Result
a10035
Figure 1. Pipelining in add operation
Chaining
Movement of array elements
Pipelining
Vector load
1 CP
For illustration only. Functional units are not physically arranged as shown.
Multiply Vector store
a10036
Figure 2. Pipelining and chaining
2.1.2 Parallel Processing: Operating System Level
At the operating system level, parallel processing is accomplished by using the
following methods:
• multiprogramming, which occurs when a processor switches between the jobs
or processes in the system.
• multiprocessing, which occurs when processors simultaneously work on as
many programs as there are processors.
4 004–2151–002Parallel Processing Issues [2]
• multitasking, which is a general term describing more than one processor
working to complete a single program. This term has become synonymous
with parallel processing.
2.1.3 Parallel Processing: Code Level
There are several ways to alter user code to take advantage of parallel
processing:
• macrotasking lets you take advantage of multitasking at the subroutine level
by inserting library calls to express parallelism. This works well on
programs that can be explicitly partitioned into tasks and can be
simultaneously executed on multiple processors.
• microtasking allows you to insert directives at the loop or block level of the
code to indicate sections that can be executed on multiple CPUs.
Macrotasking and microtasking are seldom used anymore. Autotasking is the
preferred method to use for parallel processing at the code level. Like
microtasking, Autotasking exploits parallelism at the loop or block level of
code. It has lower overhead than microtasking, and it can be made fully
automatic. It does not require any direct user intervention, but users can
interact with the system via directives and switches.
The Scienti?c Library routines were designed to be fully optimized to take
advantage of parallelism and to automatically use Autotasking during
execution.
When using the CF90 compiler, you can use the f90 -O3 command. This
command invokes aggressive optimization and Autotasking. One of the
optimization actions the compiler then performs is to substitute Scienti?c
Library routines (where appropriate) in the code. The routines are called at an
entry point where they will use less compiling time.
See the CF90 Commands and Directives Reference Manual or the f90(1) man page
for more information about using the f90 command.
2.2 Costs and Bene?ts of Parallel Processing
Parallel processing can eliminate idle CPU time because the workload is
divided among all CPUs; therefore, the amount of work performed per unit
time (the throughput) increases. However, parallel processing also introduces
some overhead into program execution. In some cases, you may be able to
004–2151–002 5Scienti?c Libraries User’s Guide
reduce wall-clock time, but at the cost of extra CPU time which increases
because more machine resources are used.
This subsection discusses these bene?ts and some of the costs of using parallel
processing.
2.2.1 Bene?ts of Parallel Processing
By using parallel processing, you can alleviate some of the following common
problems:
• Maximum-memory jobs: if the memory is occupied by a few large-memory
jobs, one or more of the CPUs might be idle even though there are other
jobs to run.
• Dedicated machine: if the computer is running a single job, then all other
CPUs are idle.
• Light workload: if the amount of jobs waiting for a CPU is less than the
total number of CPUs, then one or more of the CPUs becomes idle.
With parallel processing, the additional CPUs reduce the wall-clock time
instead of sitting idle. Even when very little idle time exists, using additional
CPUs can still lead to bene?ts.
2.2.2 Parallel Processing Overhead
Parallel processing introduces some overhead into program execution. This
subsection discusses some of the common types of overhead introduced by
parallel processing:
• Multitasked programs require more memory than unitasked programs, and
they can contain more code, more temporary variables, and can require
additional stack space.
• Multitasked jobs can be swapped more often, and remain swapped longer,
on a heavily loaded production system.
• Processors are forced to wait on semaphores during the process of
synchronization.
• Overhead is incurred when slave processors are acquired (on entry to a
parallel region) and at synchronization points within parallel regions. Tests
show that the overhead of executing extra Autotasking code adds a nominal
0% to 5% to the overall execution time.
6 004–2151–002Parallel Processing Issues [2]
• If inner-loop Autotasking is used, vector performance can decrease because
of shorter vector lengths and more vector loop startups.
• Processors are sometimes held for the next parallel region to improve
ef?ciency. While holding a processor can save time, it also costs time to
acquire and hold them.
Because overhead is associated with work distribution, jobs with large
granularity have less partitioning than smaller jobs. Large jobs, however, may
have problems with load balancing.
2.2.3 Parallelism and Vectorization
A multitasked program usually has the same amount of work for the CPUs to
perform as does a similar unitasked program. However, when the work is
spread across many processors, the wall-clock time required to complete the
work is usually less.
Vectorization is a form of parallel processing in which array elements are
processed by groups. Vectorization usually decreases both CPU time and
wall-clock time; multitasking decreases only wall-clock time. Thus,
vectorization can give you large gains in terms of saving time and have
relatively low costs associated with it.
If you make direct calls to Scienti?c Library routines, your CPU time or
wall-clock time could also be affected. Scienti?c Library routines take
advantage of vectorization and multitasking; because of the costs associated
with multitasking, you may see an increase in CPU time when using these
routines. You can control this increase somewhat by using the NCPUS
environment variable to control the maximum number of CPUs to be used on a
job. See Section 2.4.1, page 12, for details about using environment variables.
When using multitasking, the timing results in a nondedicated environment are
not always reproducible. Several factors can affect the timings obtained from
multitasked routines, including some of the following:
• System load
• I/O performed by other jobs
• Memory contention
If accurate timing results are desired, it is best to run a job in a dedicated
environment where it is the only job being run.
004–2151–002 7Scienti?c Libraries User’s Guide
2.2.4 Parallelism and Load Balancing
The parallelism for any region is determined by the number of partitions, or
chunks, of independent work the region contains. If an autotasked loop has N
iterations, N is the extent of parallelism for that loop. This means that the loop
can effectively be broken into N independent chunks of work. For autotasked
inner loops, the extent of parallelism is the number of iterations divided by the
vector length when both Autotasking and vectorization can be used.
Load balancing is the process of dividing work done by each available
processor into approximately equal amounts. In a multiuser environment, the
number of available processors is constantly changing. When Autotasking is
used, it automatically tries to perform dynamic load balancing by creating
small-granularity parallelism. For example, if a DO loop is autotasked, work is
allocated by default to each task one iteration at a time.
A direct relationship exists between load balancing and the extent of parallelism:
• The higher the extent of parallelism, the easier it is to balance the workload
evenly across the processors.
• Small-granularity parallelism is easier to balance across available processors
than large granularity parallelism.
• Small-granularity parallelism generates more overhead than large
granularity parallelism. Synchronization is required each time a chunk of
work is allocated to a processor.
2.3 Performance Issues
This subsection discusses the following different aspects used to de?ne the
performance of parallel processing: speedup, ef?ciency, and percentage of
parallelism in a program.
2.3.1 Calculating Speedups in Multitasked Programs
On a dedicated (nonproduction) system, the speedup ratio for a multitasked
program can be calculated in the following manner, where T1 is the wall-clock
execution time on a single-processor and Tp is the wall-clock execution time on
p processors:
Speedup ratio =
T1
Tp
8 004–2151–002Parallel Processing Issues [2]
(2.1)
With p CPUs, a speedup ratio as close as possible to p is desired. If the program
were completely parallel and no overhead existed, the speedup would be equal
to p (for details about the overhead associated with multitasking, see Section
2.2.2, page 6).
For example, suppose a job takes 8.7 seconds to run on a single processor.
When the job is rerun using four processors, the execution time decreases to 2.5
seconds; the speedup is the following:
s =
8:7
2:5
= 3:48
(2.2)
The speedup ratio of multitasked code has two limitations: Amdahl’s Law
(representing the speedup related to the sequential portion of the code), and
multitasking overhead (discussed in Section 2.2.2, page 6).
2.3.1.1 Amdahl’s Law
Some sections of programs, known as single-threaded code segments, must use a
single processor. Amdahl’s Law for parallel processing illustrates the effect of
single-threaded code segments on multitasking performance. Amdahl’s Law is
shown in the following equation:
s =
1
(1 f) +
f
p
(2.3)
The following components appear in this equation:
• s: Maximum expected speedup from multitasking
• p: Number of processors available for parallel execution
• f: Fraction of a program that can execute in parallel (the parallel fraction)
For example, suppose that code is 98% parallel, implying that 2% of the code
runs in serial mode. Suppose that 64 processors are available. According to
Amdahl’s Law, the maximum speedup that you can expect is:
004–2151–002 9
PGI
®
User’s Guide
Parallel Fortran, C and C++
for Scientists and Engineers
The Portland Group™
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PGI User's Guide
Copyright © 1998 – 2000, The Portland Group, Inc.
Copyright © 2000 – 2005, STMicroelectronics, Inc.
All rights reserved.
Printed in the United States of America
Part Number: 2030-990-888-0603
First Printing: Release 1.7, Jun 1998 Sixth Printing: Release 5.0, Jun 2003
Second Printing: Release 3.0, Jan 1999 Seventh Printing: Release 5.1, Nov 2003
Third Printing: Release 3.1, Sep 1999 Eight Printing: Release 5.2, Jun 2004
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Fifth Printing: Release 4.0, May 2002 Tenth Printing: Release 6.1, Dec 2005
Technical support: trs@pgroup.com
Sales: sales@pgroup.com
Web: http://www.pgroup.com/Table of Contents 3
Table of Contents
PREFACE......................................................................................................................................13
AUDIENCE DESCRIPTION..............................................................................................................13
COMPATIBILITY AND CONFORMANCE TO STANDARDS.................................................................13
ORGANIZATION............................................................................................................................14
HARDWARE AND SOFTWARE CONSTRAINTS ................................................................................15
CONVENTIONS .............................................................................................................................16
RELATED PUBLICATIONS .............................................................................................................19
GETTING STARTED ..................................................................................................................21
1.1 OVERVIEW .............................................................................................................................21
1.2 INVOKING THE COMMAND-LEVEL PGI COMPILERS................................................................22
1.2.1 Command-line Syntax....................................................................................................22
1.2.2 Command-line Options ..................................................................................................23
1.2.3 Fortran Directives and C/C++ Pragmas ........................................................................23
1.3 FILENAME CONVENTIONS ......................................................................................................24
1.3.1 Input Files ......................................................................................................................24
1.3.2 Output Files....................................................................................................................25
1.4 PARALLEL PROGRAMMING USING THE PGI COMPILERS ........................................................27
1.4.1 Running SMP Parallel Programs....................................................................................28
1.4.2 Running Data Parallel HPF Programs............................................................................28
1.5 USING THE PGI COMPILERS ON LINUX...................................................................................29
1.5.1 Linux Header Files.........................................................................................................294 Table of Contents
1.5.2 Running Parallel Programs on Linux............................................................................. 29
1.6 USING THE PGI COMPILERS ON WINDOWS ............................................................................ 30
OPTIMIZATION & PARALLELIZATION ............................................................................. 33
2.1 OVERVIEW OF OPTIMIZATION................................................................................................ 33
2.2 GETTING STARTED WITH OPTIMIZATIONS.............................................................................. 35
2.3 LOCAL AND GLOBAL OPTIMIZATION USING -O .................................................................... 37
2.3.1 Scalar SSE Code Generation.......................................................................................... 39
2.4 LOOP UNROLLING USING -MUNROLL ................................................................................... 40
2.5 VECTORIZATION USING -MVECT .......................................................................................... 41
2.5.1 Vectorization Sub-options.............................................................................................. 41
2.5.1.1 Assoc Option...........................................................................................................42
2.5.1.2 Cachesize Option .................................................................................................... 42
2.5.1.3 SSE Option ............................................................................................................. 43
2.5.1.4 Prefetch Option ....................................................................................................... 43
2.5.2 Vectorization Example Using SSE/SSE2 Instructions................................................... 44
2.6 AUTO-PARALLELIZATION USING -MCONCUR ....................................................................... 47
2.6.1 Auto-parallelization Sub-options ................................................................................... 47
2.6.1.1 Altcode Option........................................................................................................ 47
2.6.1.2 Dist Option..............................................................................................................48
2.6.1.3 Cncall Option ..........................................................................................................48
2.6.2 Loops That Fail to Parallelize ........................................................................................ 48
2.6.2.1 Innermost Loops ..................................................................................................... 49
2.6.2.2 Timing Loops.......................................................................................................... 49
2.6.2.3 Scalars..................................................................................................................... 49
2.6.2.4 Scalar Last Values................................................................................................... 50Table of Contents 5
2.7 INTER-PROCEDURAL ANALYSIS AND OPTIMIZATION USING –MIPA .......................................52
2.7.1 Building a Program Without IPA – Single Step.............................................................52
2.7.2 Building a Program Without IPA - Several Steps ..........................................................52
2.7.3 Building a Program Without IPA Using Make ..............................................................53
2.7.4 Building a Program with IPA.........................................................................................53
2.7.5 Building a Program with IPA - Single Step ...................................................................54
2.7.6 Building a Program with IPA - Several Steps ................................................................55
2.7.7 Building a Program with IPA Using Make ....................................................................56
2.7.8 Questions about IPA ......................................................................................................56
2.8 PROFILE-FEEDBACK OPTIMIZATION USING –MPFI/–MPFO.....................................................58
2.9 DEFAULT OPTIMIZATION LEVELS ..........................................................................................58
2.10 LOCAL OPTIMIZATION USING DIRECTIVES AND PRAGMAS ..................................................59
2.11 EXECUTION TIMING AND INSTRUCTION COUNTING .............................................................59
COMMAND LINE OPTIONS.....................................................................................................61
3.1 GENERIC PGI COMPILER OPTIONS .........................................................................................67
3.2 C AND C++ -SPECIFIC COMPILER OPTIONS..........................................................................122
FUNCTION INLINING .............................................................................................................129
4.1 INVOKING FUNCTION INLINING............................................................................................129
4.1.1 Using an Inline Library ................................................................................................130
4.2 CREATING AN INLINE LIBRARY............................................................................................131
4.2.1 Working with Inline Libraries......................................................................................131
4.2.2 Updating Inline Libraries - Makefiles ..........................................................................132
4.3 ERROR DETECTION DURING INLINING..................................................................................133
4.4 EXAMPLES ...........................................................................................................................1336 Table of Contents
4.5 RESTRICTIONS ON INLINING................................................................................................. 133
OPENMP DIRECTIVES FOR FORTRAN ............................................................................. 135
5.1 PARALLELIZATION DIRECTIVES ........................................................................................... 135
5.2 PARALLEL ... END PARALLEL ...................................................................................... 136
5.3 CRITICAL ... END CRITICAL .......................................................................................... 139
5.4 MASTER ... END MASTER............................................................................................... 140
5.5 SINGLE ... END SINGLE................................................................................................... 141
5.6 DO ... END DO ................................................................................................................... 142
5.7 WORKSHARE ... END WORKSHARE............................................................................. 145
5.8 BARRIER ........................................................................................................................... 145
5.9 DOACROSS ....................................................................................................................... 146
5.10 PARALLEL DO................................................................................................................ 147
5.11 PARALLEL WORKSHARE ............................................................................................ 147
5.12 SECTIONS…END SECTIONS ...................................................................................... 148
5.13 PARALLEL SECTIONS .................................................................................................. 149
5.14 ORDERED........................................................................................................................ 150
5.15 ATOMIC........................................................................................................................... 150
5.16 FLUSH.............................................................................................................................. 151
5.17 THREADPRIVATE.......................................................................................................... 151
5.18 RUN-TIME LIBRARY ROUTINES.......................................................................................... 151
5.19 ENVIRONMENT VARIABLES................................................................................................ 154
OPENMP PRAGMAS FOR C AND C++ ................................................................................. 155
6.1 PARALLELIZATION PRAGMAS .............................................................................................. 155
6.2 OMP PARALLEL..................................................................................................................... 156Table of Contents 7
6.3 OMP CRITICAL ......................................................................................................................159
6.4 OMP MASTER ........................................................................................................................160
6.5 OMP SINGLE..........................................................................................................................160
6.6 OMP FOR...............................................................................................................................161
6.7 OMP BARRIER .......................................................................................................................164
6.8 OMP PARALLEL FOR..............................................................................................................164
6.9 OMP SECTIONS......................................................................................................................165
6.10 OMP PARALLEL SECTIONS...................................................................................................165
6.11 OMP ORDERED ....................................................................................................................166
6.12 OMP ATOMIC ......................................................................................................................166
6.13 OMP FLUSH.........................................................................................................................167
6.14 OMP THREADPRIVATE.........................................................................................................167
6.15 RUN-TIME LIBRARY ROUTINES ..........................................................................................168
6.16 ENVIRONMENT VARIABLES................................................................................................171
OPTIMIZATION DIRECTIVES AND PRAGMAS ...............................................................173
7.1 ADDING DIRECTIVES TO FORTRAN.......................................................................................173
7.2 FORTRAN DIRECTIVE SUMMARY..........................................................................................174
7.3 SCOPE OF DIRECTIVES AND COMMAND LINE OPTIONS .........................................................180
7.4 ADDING PRAGMAS TO C AND C++......................................................................................181
7.5 C/C++ PRAGMA SUMMARY ................................................................................................182
7.6 SCOPE OF C/C++ PRAGMAS AND COMMAND LINE OPTIONS ...............................................185
7.7 PREFETCH DIRECTIVES ........................................................................................................188
LIBRARIES AND ENVIRONMENT VARIABLES ...............................................................191
8.1 USING BUILTIN MATH FUNCTIONS IN C/C++.......................................................................1918 Table of Contents
8.2 CREATING AND USING SHARED OBJECT FILES ON LINUX.................................................... 191
8.3 CREATING AND USING DYNAMIC-LINK LIBRARIES ON WIN32 ............................................ 193
8.4 CREATING AND USING DYNAMIC-LINK LIBRARIES ON WIN64 ............................................ 198
8.5 USING LIB3F....................................................................................................................... 206
8.6 LAPACK, THE BLAS AND FFTS......................................................................................... 206
8.7 THE C++ STANDARD TEMPLATE LIBRARY ......................................................................... 207
8.8 ENVIRONMENT VARIABLES ................................................................................................. 207
FORTRAN, C AND C++ DATA TYPES .................................................................................. 211
9.1 FORTRAN DATA TYPES ........................................................................................................ 211
9.1.1 Fortran Scalars ............................................................................................................. 211
9.1.2 FORTRAN 77 Aggregate Data Type Extensions ........................................................ 213
9.1.3 Fortran 90 Aggregate Data Types (Derived Types) ..................................................... 214
9.2 C AND C++ DATA TYPES .................................................................................................... 215
9.2.1 C and C++ Scalars ...................................................................................................... 215
9.2.2 C and C++ Aggregate Data Types .............................................................................. 217
9.2.3 Class and Object Data Layout...................................................................................... 217
9.2.4 Aggregate Alignment................................................................................................... 218
9.2.5 Bit-field Alignment...................................................................................................... 219
9.2.6 Other Type Keywords in C and C++ .......................................................................... 220
INTER-LANGUAGE CALLING.............................................................................................. 221
10.1 OVERVIEW OF CALLING CONVENTIONS ............................................................................. 221
10.2 INTER-LANGUAGE CALLING CONSIDERATIONS.................................................................. 221
10.3 FUNCTIONS AND SUBROUTINES ......................................................................................... 223
10.4 UPPER AND LOWER CASE CONVENTIONS, UNDERSCORES ................................................. 223Table of Contents 9
10.5 COMPATIBLE DATA TYPES.................................................................................................223
10.5.1 Fortran Named Common Blocks................................................................................225
10.6 ARGUMENT PASSING AND RETURN VALUES ......................................................................225
10.6.1 Passing by Value (%VAL)...........................................................................................226
10.6.2 Character Return Values ............................................................................................226
10.6.3 Complex Return Values .............................................................................................227
10.7 ARRAY INDICES .................................................................................................................227
10.8 EXAMPLE - FORTRAN CALLING C ......................................................................................228
10.9 EXAMPLE - C CALLING FORTRAN ......................................................................................229
10.10 EXAMPLE - C ++ CALLING C............................................................................................230
10.11 EXAMPLE - C CALLING C++ ............................................................................................231
10.12 EXAMPLE - FORTRAN CALLING C++...............................................................................232
10.13 EXAMPLE - C++ CALLING FORTRAN ...............................................................................234
10.14 WIN32 CALLING CONVENTIONS ......................................................................................235
10.14.1 Win32 Fortran Calling Conventions ........................................................................235
10.14.2 Symbol Name Construction and Calling Example...................................................237
10.14.3 Using the Default Calling Convention .....................................................................238
10.14.4 Using the STDCALL Calling Convention ...............................................................238
10.14.5 Using the C Calling Convention ..............................................................................239
10.14.6 Using the UNIX Calling Convention .......................................................................239
C++ NAME MANGLING ..........................................................................................................241
11.1 TYPES OF MANGLING.........................................................................................................242
11.2 MANGLING SUMMARY .......................................................................................................243
11.2.1 Type Name Mangling ................................................................................................243
11.2.2 Nested Class Name Mangling ....................................................................................243
11.2.3 Local Class Name Mangling ......................................................................................24310 Table of Contents
11.2.4 Template Class Name Mangling................................................................................ 244
RUN-TIME ENVIRONMENT.................................................................................................. 245
A1 LINUX86 AND WIN32 PROGRAMMING MODEL..................................................................... 245
A1.1 Function Calling Sequence .......................................................................................... 245
A1.2 Function Return Values ............................................................................................... 248
A1.3 Argument Passing ........................................................................................................ 250
A2 LINUX86-64 PROGRAMMING MODEL................................................................................... 253
A2.1 Function Calling Sequence .......................................................................................... 253
A2.2 Function Return Values ............................................................................................... 256
A2.3 Argument Passing ........................................................................................................ 257
A2.4 Linux86-64 Fortran Supplement.................................................................................. 262
A2.4.1 Fortran Fundamental Types .................................................................................. 262
A2.4.2 Naming Conventions............................................................................................. 263
A2.4.3 Argument Passing and Return Conventions.......................................................... 263
A2.4.4 Inter-language Calling........................................................................................... 264
A3 WIN64 PROGRAMMING MODEL ........................................................................................... 267
A3.1 Function Calling Sequence .......................................................................................... 267
A3.2 Function Return Values ............................................................................................... 269
A3.3 Argument Passing ........................................................................................................ 270
A3.4 Win64 Fortran Supplement.......................................................................................... 273
A3.4.1 Fortran Fundamental Types .................................................................................. 274
A3.4.2 Fortran Naming Conventions ................................................................................ 275
A3.4.3 Fortran Argument Passing and Return Conventions ............................................. 275
A3.4.4 Interlanguage Calling ............................................................................................ 275Table of Contents 11
MESSAGES.................................................................................................................................279
B.1 DIAGNOSTIC MESSAGES ......................................................................................................279
B.2 PHASE INVOCATION MESSAGES ..........................................................................................280
B.3 FORTRAN COMPILER ERROR MESSAGES .............................................................................280
B.3.1 Message Format...........................................................................................................280
B.3.2 Message List................................................................................................................280
B.4 FORTRAN RUNTIME ERROR MESSAGES ...............................................................................316
B.4.1 Message Format...........................................................................................................316
B.4.2 Message List................................................................................................................317
C++ DIALECT SUPPORTED ...................................................................................................321
C.1 ANACHRONISMS ACCEPTED ................................................................................................321
C.2 NEW LANGUAGE FEATURES ACCEPTED ..............................................................................323
C.3 THE FOLLOWING LANGUAGE FEATURES ARE NOT ACCEPTED...............................................325
C.4 EXTENSIONS ACCEPTED IN NORMAL C++ MODE ...............................................................325
C.5 CFRONT 2.1 COMPATIBILITY MODE .....................................................................................326
C.6 CFRONT 2.1/3.0 COMPATIBILITY MODE ...............................................................................329
INDEX..........................................................................................................................................33112 Table of ContentsPreface 13
Preface
This guide is part of a set of manuals that describe how to use The Portland Group (PGI) Fortran,
C, and C++ compilers and program development tools. In particular, these include the PGF77,
PGF95, PGHPF, PGC++, and PGCC ANSI C compilers, the PGPROF profiler, and the PGDBG
debugger. These compilers and tools work in conjunction with an x86 or x64 assembler and
linker. You can use the PGI compilers and tools to compile, debug, optimize and profile serial
and parallel applications for x86 (Intel Pentium II/III/4/M, Intel Centrino, Intel Xeon, AMD
Athlon XP/MP) or x64 (AMD Athlon64/Opteron/Turion, Intel EM64T) processor-based systems.
This PGI User's Guide provides operating instructions for the command-level compilation
environment and general information about PGI’s implementation of the Fortran, C, and C++
languages. This guide does not teach the Fortran, C, or C++ programming languages.
Audience Description
This guide is intended for scientists and engineers using the PGI compilers. To use these
compilers, you should be aware of the role of high-level languages (e.g. Fortran, C, C++) and
assembly-language in the software development process and should have some level of
understanding of programming. The PGI compilers are available on a variety of x86 or x64
hardware platforms and operating systems. You need to be familiar with the basic commands
available on your system.
Finally, your system needs to be running a properly installed and configured version of the
compilers. For information on installing PGI compilers and tools, refer to the installation
instructions.
Compatibility and Conformance to Standards
For further information, refer to the following:
• American National Standard Programming Language FORTRAN, ANSI X3. -1978 (1978).
• ISO/IEC 1539 : 1991, Information technology – Programming Languages – Fortran,
Geneva, 1991 (Fortran 90).
• ISO/IEC 1539 : 1997, Information technology – Programming Languages – Fortran,
Geneva, 1997 (Fortran 95).
• Fortran 95 Handbook Complete ISO/ANSI Reference, Adams et al, The MIT Press,
Cambridge, Mass, 1997. 14 Preface
• High Performance Fortran Language Specification, Revision 1.0, Rice University, Houston,
Texas (1993), http://www.crpc.rice.edu/HPFF.
• High Performance Fortran Language Specification, Revision 2.0, Rice University, Houston,
Texas (1997), http://www.crpc.rice.edu/HPFF.
• OpenMP Fortran Application Program Interface, Version 1.1, November 1999,
http://www.openmp.org.
• OpenMP C and C++ Application Program Interface, Version 1.0, October 1998,
http://www.openmp.org.
• Programming in VAX Fortran, Version 4.0, Digital Equipment Corporation (September,
1984).
• IBM VS Fortran, IBM Corporation, Rev. GC26-4119.
• Military Standard, Fortran, DOD Supplement to American National Standard Programming
Language Fortran, ANSI x.3-1978, MIL-STD-1753 (November 9, 1978).
• American National Standard Programming Language C, ANSI X3.159-1989.
Organization
This manual is divided into the following chapters and appendices:
Chapter 1 Getting Started provides an introduction to the PGI compilers and
describes their use and overall features.
Chapter 2 Optimization & Parallelization describes standard optimization
techniques that, with little effort, allow users to significantly improve the
performance of programs.
Chapter 3 Command Line Options provides a detailed description of each
command-line option.
Chapter 4 Function Inlining describes how to use function inlining and shows how
to create an inline library.
Chapter 5 OpenMP Directives for Fortran provides a description of the OpenMP
Fortran parallelization directives and shows examples of their use.
Chapter 6 OpenMP Pragmas for C and C++ provides a description of the OpenMP
C and C++ parallelization pragmas and shows examples of their use. Preface 15
Chapter 7 Optimization Directives and Pragmas provides a description of each
Fortran optimization directive and C/C++ optimization pragma, and
shows examples of their use.
Chapter 8 Libraries and Environment Variables discusses PGI support libraries,
shared object files, and environment variables that affect the behavior of
the PGI compilers.
Chapter 9 Fortran, C and C++ Data Types describes the data types that are
supported by the PGI Fortran, C, and C++ compilers.
Chapter 10 Inter-language Calling provides examples showing how to place C
Language calls in a Fortran program and Fortran Language calls in a C
program.
Chapter 11 C++ Name Mangling describes the name mangling facility and explains
the transformations of names of entities to names that include information
on aspects of the entity’s type and a fully qualified name.
Appendix A Run-time Environment describes the assembly language calling
conventions and examples of assembly language calls.
Appendix B Messages provides a list of compiler error messages.
Appendix C C++ Dialect Supported lists more details of the version of the C++
language that PGC++ supports.
Hardware and Software Constraints
This guide describes versions of the PGI compilers that produce assembly code for x86 and x64
processor-based systems. Details concerning environment-specific values and defaults and
system-specific features or limitations are presented in the release notes sent with the PGI
compilers. 16 Preface
Conventions
The PGI User's Guide uses the following conventions:
italic is used for commands, filenames, directories, arguments, options and for
emphasis.
Constant Width is used in examples and for language statements in the text, including
assembly language statements.
[ item1 ] square brackets indicate optional items. In this case item1 is optional.
{ item2 | item 3} braces indicate that a selection is required. In this case, you must select
either item2 or item3.
filename ... ellipsis indicate a repetition. Zero or more of the preceding item may
occur. In this example, multiple filenames are allowed.
FORTRAN Fortran language statements are shown in the text of this guide using
upper-case characters and a reduced point size.
The PGI compilers and tools are supported on both 32-bit and 64-bit variants of the Linux and
Windows operating systems on a variety of x86-compatible processors. There are a wide variety
of releases and distributions of each of these types of operating systems. The PGI User’s Guide
defines the following terms with respect to these platforms:
x86 a processor designed to be binary compatible with i386/i486 and
previous generation processors from Intel* Corporation. Used to refer
collectively to such processors up to and including 32-bit variants.
IA32 an Intel Architecture 32-bit processor designed to be binary compatible
with x86 processors, but incorporating new features such as streaming
SIMD extensions (SSE) for improved performance.
AMD64 a 64-bit processor from AMD designed to be binary compatible with
IA32 processors, and incorporating new features such as additional
registers and 64-bit addressing support for improved performance and
greatly increased memory range.
EM64T a 64-bit IA32 processor with Extended Memory 64-bit Technology
extensions that are binary compatible with AMD64 processors.
x64 collectively, all AMD64 and EM64T processors supported by the PGI
compilers. Preface 17
linux86 32-bit Linux operating system running on an x86 or x64 processorbased system, with 32-bit GNU tools, utilities and libraries used by the
PGI compilers to assemble and link for 32-bit execution.
linux86-64 64-bit Linux operating system running on an x64 processor-based
system, with 64-bit and 32-bit GNU tools, utilities and libraries used
by the PGI compilers to assemble and link for execution in either
linux86 or linux86-64 environments. The 32-bit development tools and
execution environment under linux86-64 are considered a cross
development environment for x86 processor-based applications.
Win32 any of the 32-bit Microsoft Windows Operating Systems
(XP/2000/Server 2003) running on an x86 or x64 processor-based
system. On these targets, the PGI compiler products include additional
tools and libraries needed to build executables for 32-bit Windows
systems.
Win64 any of the 64-bit Microsoft Windows Operating Systems (XP
Professional /Windows Server 2003 x64 Editions) running on an x64
processor-based system. On these targets, the PGI compiler products
require the co-installation of a Microsoft Platform SDK to build
executables for 64-bit Windows systems.
Windows collectively, all Win32 and Win64 platforms supported by the PGI
compilers.
The following table lists the PGI compilers and tools and their corresponding commands:
Table P-1: PGI Compilers and Commands
Compiler or
Tool
Language or Function Command
PGF77 FORTRAN 77 pgf77
PGF95 Fortran 90/95 pgf95
PGHPF High Performance Fortran pghpf
PGCC C ANSI C99 and K&R C pgcc
PGC++ ANSI C++ with cfront features pgCC 18 Preface
Compiler or
Tool
Language or Function Command
PGDBG Source code debugger pgdbg
PGPROF Performance profiler pgprof
In general, the designation PGF95 is used to refer to The Portland Group’s Fortran 90/95
compiler, and pgf95 is used to refer to the command that invokes the compiler. A similar
convention is used for each of the PGI compilers and tools.
For simplicity, examples of command-line invocation of the compilers generally reference the
pgf95 command and most source code examples are written in Fortran. Usage of the PGF77
compiler, whose features are a subset of PGF95, is similar. Usage of PGHPF, PGC++, and
PGCC ANSI C99 is consistent with PGF95 and PGF77, but there are command-line options and
features of these compilers that do not apply to PGF95 and PGF77 (and vice versa).
There are a wide variety of x86-compatible processors in use. All are supported by the PGI
compilers and tools. Most of these processors are forward-compatible, but not backwardcompatible. That means code compiled to target a given processor will not necessarily execute
correctly on a previous-generation processor. The most important processor types, along with a
list of the features utilized by the PGI compilers that distinguish them from a compatibility
standpoint, are listed in Table P-2:
Table P-2: Processor Options
Processor Prefetch SSE1 SSE2 SSE3 32-bit 64-bit
Scalar FP
Default
AMD Athlon X x87
AMD Athlon XP/MP X X X x87
AMD Athlon64 X X X X X SSE
AMD Opteron X X X X X SSE
AMD Opteron Rev E X X X X X X SSE
AMD Turion X X X X X X SSE
Intel Celeron X x87
Intel Pentium II X x87
Intel Pentium III X X X x87 Preface 19
Processor Prefetch SSE1 SSE2 SSE3 32-bit 64-bit
Scalar FP
Default
Intel Pentium 4 X X X X SSE
Intel Pentium M X X X X SSE
Intel Centrino X X X X SSE
Intel Pentium 4 EM64T X X X X X X SSE
Intel Xeon EM64T X X X X X X SSE
In this manual, the convention is to use “x86” to specify the group of processors in Table P-2 that
are listed “32-bit” but not “64-bit.” The convention is to use x64 to specify the group of
processors that are listed as both “32-bit” and “64-bit.” x86 processor-based systems can run only
under 32-bit operating systems. x64 processor-based systems can run either 32-bit or 64-bit
operating systems, and can execute all 32-bit x86 binaries in either case. x64 processors have
additional registers and 64-bit addressing capabilities that are utilized by the PGI compilers and
tools when operating under a 64-bit operating system. The prefetch, SSE1, SSE2 and SSE3
processor features further distinguish the various processors. Where such distinctions are
important with respect to a given compiler option or feature, it is explicitly noted in this manual.
Note that the default for performing scalar floating-point arithmetic is to use SSE instructions on
targets that support SSE1 and SSE2. See section 2.3.1, Scalar SSE Code Generation, for a
detailed discussion of this topic.
Related Publications
The following documents contain additional information related to the x86 and x64 architectures,
and the compilers and tools available from The Portland Group.
• PGI Fortran Reference manual describes the FORTRAN 77, Fortran 90/95, and HPF
statements, data types, input/output format specifiers, and additional reference material
related to use of the PGI Fortran compilers.
• System V Application Binary Interface Processor Supplement by AT&T UNIX System
Laboratories, Inc. (Prentice Hall, Inc.).
• System V Application Binary Interface X86-64 Architecture Processor Supplement,
http://www.x86-64.org/abi.pdf.
• Fortran 95 Handbook Complete ISO/ANSI Reference, Adams et al, The MIT Press,
Cambridge, Mass, 1997. 20 Preface
• Programming in VAX Fortran, Version 4.0, Digital Equipment Corporation (September,
1984).
• IBM VS Fortran, IBM Corporation, Rev. GC26-4119.
• The C Programming Language by Kernighan and Ritchie (Prentice Hall).
• C: A Reference Manual by Samuel P. Harbison and Guy L. Steele Jr. (Prentice Hall,
1987).
• The Annotated C++ Reference Manual by Margaret Ellis and Bjarne Stroustrup, AT&T
Bell Laboratories, Inc. (Addison-Wesley Publishing Co., 1990).
• OpenMP Application Program Interface , Version 2.5 May 2005 (OpenMP Architecture
Review Board, 1997-2005). Getting Started 21
Chapter 1
Getting Started
This chapter describes how to use the PGI compilers. The command used to invoke a compiler,
for example the pgf95 command, is called a compiler driver. The compiler driver controls the
following phases of compilation: preprocessing, compiling, assembling, and linking. Once a file is
compiled and an executable file is produced, you can execute, debug, or profile the program on
your system. Executables produced by the PGI compilers are unconstrained, meaning they can be
executed on any compatible x86 or x64 processor-based system regardless of whether the PGI
compilers are installed on that system.
1.1 Overview
In general, using a PGI compiler involves three steps:
1. Produce a program in a file containing a .f extension or another appropriate extension
(see Section 1.3.1 Input Files). This may be a program that you have written or a
program that you are modifying.
2. Compile the program using the appropriate compiler command.
3. Execute, debug, or profile the executable file on your system.
The PGI compilers allow many variations on these general program development steps. These
variations include the following:
• Stop the compilation after preprocessing, compiling or assembling to save and examine
intermediate results.
• Provide options to the driver that control compiler optimization or that specify various
features or limitations.
• Include as input intermediate files such as preprocessor output, compiler output, or assembler
output. 22 Chapter 1
1.2 Invoking the Command-level PGI Compilers
To translate and link a Fortran, C, or C++ language program, the pgf77, pgf95, pghpf, pgcc,
and pgCC commands do the following:
• Preprocess the source text file
• Check the syntax of the source text
• Generate an assembly language file
• Pass control to the subsequent assembly and linking steps
For example, if you enter the following simple Fortran program in the file hello.f:
print *, “hello”
end
You can compile it from a shell prompt using the default pgf95 driver options.
PGI$ pgf95 hello.f
Linking:
PGI$
By default, the executable output is placed in the file a.out (a.exe on Win32 platforms, and a
filename based on the name of the first source or object file on the command line on Win64). Use
the –o option to specify an output file name. To place the executable output in the file hello:
PGI$ pgf95 –o hello hello.f
Linking:
PGI$
To execute the resulting program, simply type the filename at the command prompt and press the
Return or Enter key on your keyboard:
PGI$ hello
hello
PGI$
1.2.1 Command-line Syntax
The command-line syntax, using pgf95 as an example, is:
pgf95 [options] [ path] filename [...]Getting Started 23
Where:
options is one or more command-line options, all of which are described in detail
in Chapter 3, Command Line Options. Case is significant for options and
their arguments.
The compiler drivers recognize characters preceded by a hyphen (-) as
command-line options. For example, the –Mlist option specifies that the
compiler creates a listing file (in the text of this manual we show
command-line options using a dash instead of a hyphen, for example
–Mlist). In addition, the pgCC command recognizes a group of characters
preceded by a plus sign (+) as command-line options.
The order of options and the filename is not fixed. That is, you can place
options before and after the filename argument on the command line.
However, the placement of some options is significant, for example the –l
option.
Note: If two or more options contradict each other, the last one in the
command line takes precedence.
path is the pathname to the directory containing the file named by filename. If
you do not specify path for a filename, the compiler uses the current
directory. You must specify path separately for each filename not in the
current directory.
filename is the name of a source file, assembly-language file, object file, or library
to be processed by the compilation system. You can specify more than one
[path]f ilename.
1.2.2 Command-line Options
The command-line options control various aspects of the compilation process. For a complete
alphabetical listing and a description of all the command-line options, refer to Chapter 3,
Command Line Options.
1.2.3 Fortran Directives and C/C++ Pragmas
Fortran directives or C/C++ pragmas inserted in program source code allow you to alter the
effects of certain command-line options and control various aspects of the compilation process for
a specific routine or a specific program loop. For a complete alphabetical listing and a description
of all the Fortran directives and C/C++ pragmas, refer to Chapter 5, OpenMP Directives for 24 Chapter 1
Fortran, Chapter 6, OpenMP Pragmas for C and C++, and Chapter 7, Optimization Directives
and Pragmas.
1.3 Filename Conventions
The PGI compilers use the filenames that you specify on the command line to find and to create
input and output files. This section describes the input and output filename conventions for the
phases of the compilation process.
1.3.1 Input Files
You can specify assembly-language files, preprocessed source files, Fortran/C/C++ source files,
object files, and libraries as inputs on the command line. The compiler driver determines the type
of each input file by examining the filename extensions. The drivers use the following
conventions:
filename.f indicates a Fortran source file.
filename.F indicates a Fortran source file that can contain macros and preprocessor
directives (to be preprocessed).
filename.F95 indicates a Fortran 90/95 source file that can contain macros and
preprocessor directives (to be preprocessed).
filename.f90 indicates a Fortran 90/95 source file that is in freeform format.
filename.f95 indicates a Fortran 90/95 source file that is in freeform format.
filename.hpf indicates an HPF source file.
filename.c indicates a C source file that can contain macros and preprocessor
directives (to be preprocessed).
filename.i indicates a pre-processed C or C++ source file.
filename.C indicates a C++ source file that can contain macros and preprocessor
directives (to be preprocessed).
filename.cc indicates a C++ source file that can contain macros and preprocessor
directives (to be preprocessed).
filename.s indicates an assembly-language file.
filename.o indicates an object file.
filename.a indicates a library of object files. Getting Started 25
filename.so (Linux systems only) indicates a library of shared object files.
filename.dll (Windows systems only) indicates a dynamically linked library (DLL) of
object files.
The driver passes files with .s extensions to the assembler and files with .o, .so, .a and .dll
extensions to the linker. Input files with unrecognized extensions, or no extension, are also passed
to the linker.
Files with a .F (Capital F) suffix are first preprocessed by the Fortran compilers and the output is
passed to the compilation phase. The Fortran preprocessor functions similar to cpp for C/C++
programs, but is built in to the Fortran compilers rather than implemented through an invocation
of cpp. This ensures consistency in the pre-processing step regardless of the type or revision of
operating system under which you’re compiling.
Any input files not needed for a particular phase of processing are not processed. For example, if
on the command line you use an assembly-language file (filename.s) and the –S option to stop
before the assembly phase, the compiler takes no action on the assembly-language file. Processing
stops after compilation and the assembler does not run (in this case compilation must have been
completed in a previous pass which created the .s file). Refer to the following section, Output
Files, for a description of the –S option.
In addition to specifying primary input files on the command line, code within other files can be
compiled as part of “include” files using the INCLUDE statement in a Fortran source file or the
preprocessor #include directive in Fortran source files that use a .F extension or C and C++
source files.
When linking a program with a library, the linker extracts only those library components that the
program needs. The compiler drivers link in several libraries by default. For more information
about libraries, refer to Chapter 8, Libraries.
1.3.2 Output Files
By default, an executable output file produced by one of the PGI compilers is placed in the file
a.out (a.exe on Win32 platforms, and a filename based on the name of the first source or object
file on the command line on Win64). As shown in the preceding section, you can use the –o
option to specify the output file name.
If you use one of the options: –F (Fortran only), –P (C/C++ only), –S or –c, the compiler
produces a file containing the output of the last phase that completes for each input file, as
specified by the option supplied. The output file will be a preprocessed source file, an assemblylanguage file, or an unlinked object file respectively. Similarly, the –E option does not produce a
file, but displays the preprocessed source file on the standard output. Using any of these options, 26 Chapter 1
the –o option is valid only if you specify a single input file. If no errors occur during processing,
you can use the files created by these options as input to a future invocation of any of the PGI
compiler drivers. The following table lists the stop after options and the output files that the
compilers create when you use these options.
Table 1-1: Stop after Options, Inputs and Outputs
Option Stop after Input Output
–E preprocessing Source files (must have .F
extension for Fortran)
preprocessed file to
standard out
–F preprocessing Source files (must have .F
extension, this option is not
valid for pgcc or pgCC)
preprocessed file – .f
–P preprocessing Source files (this option is
not valid for pgf77, pgf95
or pghpf)
preprocessed file – .i
–S compilation Source files or preprocessed
files
assembly-language
file – .s
–c assembly Source files, preprocessed
files or assembly-language
files
unlinked object
file – .o
none linking Source files, preprocessed
files, assembly-language
files, object files or libraries
executable files
a.out
If you specify multiple input files or do not specify an object filename, the compiler uses the input
filenames to derive corresponding default output filenames of the following form, where filename
is the input filename without its extension:
filename.f indicates a preprocessed file (if you compiled a Fortran file using the
–F option).
filename.lst indicates a listing file from the –Mlist option.
filename.o indicates an object file from the –c option.
filename.s indicates an assembly-language file from the –S option.
Note: Unless you specify otherwise, the destination directory for any
output file is the current working directory. If the file exists in the
destination directory, the compiler overwrites it. Getting Started 27
The following example demonstrates the use of output filename extensions.
$ pgf95 –c proto.f proto1.F
This produces the output files proto.o and proto1.o, both of which are binary object files. Prior
to compilation, the file proto1.F is pre-processed because it has a .F filename extension.
1.4 Parallel Programming Using the PGI Compilers
The PGI compilers support three styles of parallel programming:
• Automatic shared-memory parallel programs compiled using the -Mconcur option to pgf77,
pgf95, pgcc, or pgCC — parallel programs of this variety can be run on shared-memory
parallel (SMP) systems such as dual-core or multi-processor workstations.
• OpenMP shared-memory parallel programs compiled using the -mp option to pgf77,
pgf95, pgcc, or pgCC — parallel programs of this variety can be run on SMP systems.
Carefully coded user-directed parallel programs using OpenMP directives can often achieve
significant speed-ups on dual-core workstations or large numbers of processors on SMP
server systems. Chapter 5, OpenMP Directives for Fortran, and Chapter 6, OpenMP
Pragmas for C and C++, contain complete descriptions of user-directed parallel
programming.
• Data parallel shared- or distributed-memory parallel programs compiled using the PGHPF
High Performance Fortran compiler — parallel programs of this variety can be run on SMP
workstations or servers, distributed-memory clusters of workstations, or clusters of SMP
workstations or servers. Coding a data parallel version of an application can be more work
than using OpenMP directives, but has the advantage that the resulting executable is usable
on all types of parallel systems regardless of whether shared memory is available. See the
PGHPF User’s Guide for a complete description of how to build and execute data parallel
HPF programs.
In this manual, the first two types of parallel programs are collectively referred to as SMP parallel
programs. The third type is referred to as a data parallel program, or simply as an HPF program.
Some newer CPUs incorporate two or more complete processor cores (functional units, registers,
level 1 cache, level 2 cache, etc) on a single silicon die. These are referred to as multi-core
processors. For purposes of OpenMP, threads, or HPF parallelism, these cores function as 2 or
more distinct processors. However, the processing cores are on a single chip occupying a single
socket on a system motherboard. For purposes of PGI software licensing, a multi-core processor
is treated as a single CPU. 28 Chapter 1
1.4.1 Running SMP Parallel Programs
When you execute an SMP parallel program, by default it will use only 1 processor. To run on
more than one processor, set the NCPUS environment variable to the desired number of
processors (subject to a maximum of 4 for PGI’s workstation-class products).
You can set this environment variable by issuing the following command:
% setenv NCPUS
in a shell command window under csh, or with
% NCPUS=; export NCPUS
in sh, ksh, or BASH command window.
Note: If you set NCPUS to a number larger than the number of physical
processors, your program will execute very slowly.
1.4.2 Running Data Parallel HPF Programs
When you execute an HPF program, by default it will use only one processor. If you wish to run
on more than one processor, use the -pghpf -np runtime option. For example, to compile and run
the hello.f example defined above on one processor, you would issue the following commands:
% pghpf –o hello hello.f
Linking:
% hello
hello
%
To execute it on two processors, you would issue the following commands:
% hello -pghpf -np 2
hello
%
Note: If you specify a number larger than the number of physical
processors, your program will execute very slowly.
Note that you still only see a single “hello” printed to your screen. This is because HPF is a
single-threaded model, meaning that all statements execute with the same semantics as if they Getting Started 29
were running in serial. However, parallel statements or constructs operating on explicitly
distributed data are in fact executed in parallel. The programmer must manually insert compiler
directives to cause data to be distributed to the available processors. See the PGHPF User’s
Guide and The High Performance Fortran Handbook for more details on constructing and
executing data parallel programs on shared-memory or distributed-memory cluster systems using
PGHPF.
1.5 Using the PGI Compilers on Linux
1.5.1 Linux Header Files
The Linux system header files contain many GNU gcc extensions. Many of these extensions are
supported. This should allow the PGCC C and C++ compilers to compile most programs
compilable with the GNU compilers. A few header files not interoperable with previous revisions
of the PGI compilers have been rewritten and are included in $PGI/linux86/include. These files
are: sigset.h, asm/byteorder.h, stddef.h, asm/posix_types.h and others. Also, PGI’s version of
stdarg.h should support changes in newer versions of Linux.
If you are using the PGCC C or C++ compilers, please make sure that the supplied versions of
these include files are found before the system versions. This will happen by default unless you
explicitly add a –I option that references one of the system include directories.
1.5.2 Running Parallel Programs on Linux
You may encounter difficulties running auto-parallel or OpenMP programs on Linux systems
when the per-thread stack size is set to the default (2MB). If you have unexplained failures, please
try setting the environment variable MPSTKZ to a larger value, such as 8MB. This can be
accomplished with the command:
% setenv MPSTKZ 8M
in csh, or with
% MPSTKZ=8M; export MPSTKZ
in bash, sh, or ksh.
If your program is still failing, you may be encountering the hard 8 MB limit on main process
stack sizes in Linux. You can work around the problem by issuing the command:
% limit stacksize unlimited
in csh, or 30 Chapter 1
% ulimit -s unlimited
in bash, sh, or ksh.
1.6 Using the PGI Compilers on Windows
On Windows platforms, the tools that ship with the PGI Workstation or PGI Server commandlevel compilers include a full-featured shell command environment. After installation, you should
have a PGI icon on your Windows desktop. Double-left-click on this icon to cause an instance of
the BASH command shell to appear on your screen. Working within BASH is very much like
working within the sh or ksh shells on a Linux system, but in addition BASH has a command
history feature similar to csh and several other unique features. Shell programming is fully
supported. A complete BASH User’s Guide is available through the PGI online manual set. Select
“PGI Workstation” under Start->Programs and double-left-click on the documentation icon to see
the online manual set. You must have a web browser installed on your system in order to read the
online manuals.
The BASH shell window is pre-initialized for usage of the PGI compilers, so there is no need to
set environment variables or modify your command path when the command window comes up.
In addition to the PGI compiler commands referenced above, within BASH you have access to
over 100 common commands and utilities, including but not limited to the following:
vi emacs make
tar / untar gzip / gunzip ftp
sed grep / egrep / fgrep awk
cat cksum cp
date diff du
find kill ls
more / less mv printenv / env
rm / rmdir touch wc
If you are familiar with program development in a Linux environment, editing, compiling, and
executing programs within BASH will be very comfortable. If you have not previously used such
an environment, you should take time to familiarize yourself with either the vi or emacs editors
and with makefiles. The emacs editor has an extensive online tutorial, which you can start by
bringing up emacs and selecting the appropriate option under the pull-down help menu. You can Getting Started 31
get a thorough introduction to the construction and use of makefiles through the online Makefile
User’s Guide. Optimization & Parallelization 33
Chapter 2
Optimization & Parallelization
Source code that is readable, maintainable, and produces correct results is not always organized
for efficient execution. Normally, the first step in the program development process involves
producing code that executes and produces the correct results. This first step usually involves
compiling without much worry about optimization. After code is compiled and debugged, code
optimization and parallelization become an issue. Invoking one of the PGI compiler commands
with certain options instructs the compiler to generate optimized code. Optimization is not always
performed since it increases compilation time and may make debugging difficult. However,
optimization produces more efficient code that usually runs significantly faster than code that is
not optimized.
The compilers optimize code according to the specified optimization level. Using the –O,
–Mvect, –Mipa and –Mconcur options, you can specify the optimization levels. In addition,
several additional –M switches can be used to control specific types of optimization and
parallelization.
This chapter describes the optimization options and describes how to choose optimization options
to use with the PGI compilers. Chapter 4, Function Inlining, describes how to use the function
inlining options.
2.1 Overview of Optimization
In general, optimization involves using transformations and replacements that generate more
efficient code. This is done by the compiler and involves replacements that are independent of the
particular target processor’s architecture as well as replacements that take advantage of the
x86 or x64 architecture, instruction set and registers. For the discussion in this and the following
chapters, optimization is divided into the following categories:
Local Optimization
This optimization is performed on a block-by-block basis within a program’s basic blocks. A
basic block is a sequence of statements, in which the flow of control enters at the beginning and
leaves at the end without the possibility of branching, except at the end. The PGI compilers
perform many types of local optimization including: algebraic identity removal, constant folding,
common sub-expression elimination, pipelining, redundant load and store elimination, scheduling,
strength reduction, and peephole optimizations. 34 Chapter 2
Global Optimization
This optimization is performed on a program unit over all its basic blocks. The optimizer
performs control-flow and data-flow analysis for an entire program unit. All loops, including
those formed by IFs and GOTOs are detected and optimized. Global optimization includes:
constant propagation, copy propagation, dead store elimination, global register allocation,
invariant code motion, and induction variable elimination.
Loop Optimization: Unrolling, Vectorization, and Parallelization
The performance of certain classes of loops may be improved through vectorization or unrolling
options. Vectorization transforms loops to improve memory access performance and make use of
packed SSE instructions which perform the same operation on multiple data items concurrently.
Unrolling replicates the body of loops to reduce loop branching overhead and provide better
opportunities for local optimization, vectorization and scheduling of instructions. Performance for
loops on systems with multiple processors may also improve using the parallelization features of
the PGI compilers.
Inter-Procedural Analysis and Optimization (IPA)
Interprocedural analysis allows use of information across function call boundaries to perform
optimizations that would otherwise be unavailable. For example, if the actual argument to a
function is in fact a constant in the caller, it may be possible to propagate that constant into the
callee and perform optimizations that are not valid if the dummy argument is treated as a variable.
A wide range of optimizations are enabled or improved by using IPA, including but not limited to
data alignment optimizations, argument removal, constant propagation, pointer disambiguation,
pure function detection, F90/F95 array shape propagation, data placement, vestigial function
removal, automatic function inlining, inlining of functions from pre-compiled libraries, and
interprocedural optimization of functions from pre-compiled libraries.
Function Inlining
This optimization allows a call to a function to be replaced by a copy of the body of that function.
This optimization will sometimes speed up execution by eliminating the function call and return
overhead. Function inlining may also create opportunities for other types of optimization.
Function inlining is not always beneficial. When used improperly it may increase code size and
generate less efficient code.
Profile-Feedback Optimization (PFO)
Profile-feedback optimization makes use of information from a trace file produced by specially
instrumented executables which capture and save information on branch frequency, function and
subroutine call frequency, semi-invariant values, loop index ranges, and other input data Optimization & Parallelization 35
dependent information that can only be collected dynamically during execution of a program. By
definition, use of profile-feedback optimization is a two-phase process: compilation and execution
of a specially-instrumented executable, followed by a subsequent compilation which reads a trace
file generated during the first phase and uses the information in the trace file to guide compiler
optimizations.
2.2 Getting Started with Optimizations
Your first concern should be getting your program to execute and produce correct results. To get
your program running, start by compiling and linking without optimization. Use the optimization
level –O0 or select –g to perform minimal optimization. At this level, you will be able to debug
your program easily and isolate any coding errors exposed during porting to x86 or x64 platforms.
If you want to get started quickly with optimization, a good set of options to use with any of the
PGI compilers is –fastsse –Mipa=fast. For example:
$ pgf95 –fastsse –Mipa=fast prog.f
For all of the PGI Fortran, C, and C++ compilers, this option will generally produce code that is
well-optimized without the possibility of significant slowdowns due to pathological cases. The
-fastsse option is an aggregate option that includes a number of individual PGI compiler options;
which PGI compiler options are included depends on the target for which compilation is
performed. The –Mipa=fast option invokes interprocedural analysis including several IPA
suboptions.
For C++ programs, add -Minline=levels:10 --no_exceptions:
$ pgCC –fastsse –Mipa=fast –Minline=levels:10 ––no_exceptions prog.cc
Note: a C++ program compiled with ––no_execptions will fail if the program uses exception
handling.
By experimenting with individual compiler options on a file-by-file basis, further significant
performance gains can sometimes be realized. However, individual optimizations can sometimes
cause slowdowns depending on coding style and must be used carefully to ensure performance
improvements result. In addition to –fastsse, the optimization flags most likely to further improve
performance are –O3, –Mpfi/–Mpfo, –Minline, and on targets with multiple processors
–Mconcur. In addition, the –Msafeptr option can significantly improve performance of C/C++
programs in which there is known to be no pointer aliasing. However, for obvious reasons this
command-line option must be used carefully. 36 Chapter 2
Three other options which are extremely useful are –help, –Minfo, and –dryrun. You can see a
specification of any command-line option by invoking any of the PGI compilers with –help in
combination with the option in question, without specifying any input files.
For example:
$ pgf95 –help –fastsse
Reading rcfile /usr/pgi_rel/linux86-64/6.0/bin/.pgf95rc
-fastsse == -fast -Mvect=sse -Mcache_align –Mflushz
-fast Common optimizations: -O2 -Munroll=c:1 -Mnoframe -Mlre
. . .
Or to see the full functionality of –help itself, which can return information on either an individual
option or groups of options by type:
$ pgf95 –help –help
Reading rcfile /usr/pgi_rel/linux86-64/6.0/bin/.pgf95rc
-help[=groups|asm|debug|language|linker|opt|other|overall|
phase|prepro|suffix|switch|target|variable]
The –Minfo option can be used to display compile-time optimization listings. When this option is
used, the PGI compilers will issue informational messages to stdout as compilation proceeds.
From these messages, you can determine which loops are optimized using unrolling, SSE
instructions, vectorization, parallelization, interprocedural optimizations and various
miscellaneous optimizations. You can also see where and whether functions are inlined. The
–Mneginfo option can be used to display informational messages listing why certain optimizations
are inhibited.
The –dryrun option can be useful as a diagnostic tool if you need to see the steps used by the
compiler driver to pre-process, compile, assemble and link in the presence of a given set of
command line inputs. When you specify the –dryrun option, these steps will be printed to stdout
but will not actually be performed. For example, this allows inspection of the default and userspecified libraries that are searched during the link phase, and the order in which they are
searched by the linker.
The remainder of this chapter describes the –O options, the loop unroller option –Munroll, the
vectorizer option –Mvect, the auto-parallelization option –Mconcur, and the inter-procedural
analysis optimization –Mipa, and the profile-feedback instrumentation (–Mpfi) and optimization
(–Mpfo) options. Usually, you should be able to get very near optimal compiled performance
using some combination of these switches. The following overview will help if you are just
getting started with one of the PGI compilers, or wish to experiment with individual
optimizations. Complete specifications of each of these options are listed in Chapter 3,
Command Line Options.Optimization & Parallelization 37
The chapters that follow provide more detailed information on other –M options that
control specific optimizations, including function inlining. Explicit parallelization through the
use of OpenMP directives or pragmas is invoked using the –mp option, described in detail in
Chapter 5, OpenMP Directives for Fortran, and Chapter 6, OpenMP Pragmas for C and C++.
2.3 Local and Global Optimization using -O
Using the PGI compiler commands with the –Olevel option, you can specify any of the following
optimization levels (the capital O is for Optimize):
–O0 level-zero specifies no optimization. A basic block is generated for each
Fortran, C or C++ statement.
–O1 level-one specifies local optimization. Scheduling of basic blocks is
performed. Register allocation is performed.
–O2 level-two specifies global optimization. This level performs all level-one
local optimization as well as level-two global optimization.
–O3 level-three specifies aggressive global optimization. This level performs
all level-one and level-two optimizations and enables more aggressive
hoisting and scalar replacement optimizations that may or may not be
profitable.
Level-zero optimization specifies no optimization (–O0). At this level, the compiler generates a
basic block for each statement. This level is useful for the initial execution of a program.
Performance will almost always be slowest using this optimization level. Level-zero is useful for
debugging since there is a direct correlation between the program text and the code generated.
Level-one optimization specifies local optimization (–O1). The compiler performs scheduling of
basic blocks as well as register allocation. This optimization level is a good choice when the code
is very irregular; that is it contains many short statements containing IF statements and the
program does not contain loops (DO or DO WHILE statements). For certain types of code, this
optimization level may perform better than level-two (–O2) although this case rarely occurs.
The PGI compilers perform many different types of local optimizations, including but not limited
to:
• Algebraic identity removal
• Constant folding
• Common subexpression elimination
• Local register optimization 38 Chapter 2
• Peephole optimizations
• Redundant load and store elimination
• Strength reductions
Level-two optimization (–O2 or –O) specifies global optimization. The –fast option generally will
specify global optimization; however, the –fast switch will vary from release to release depending
on a reasonable selection of switches for any one particular release. The –O or –O2 level performs
all level-one local optimizations as well as global optimizations. Control flow analysis is applied
and global registers are allocated for all functions and subroutines. Loop regions are given special
consideration. This optimization level is a good choice when the program contains loops, the
loops are short, and the structure of the code is regular.
The PGI compilers perform many different types of global optimizations, including but not
limited to:
• Branch to branch elimination
• Constant propagation
• Copy propagation
• Dead store elimination
• Global register allocation
• Invariant code motion
• Induction variable elimination
You select the optimization level on the command line. For example, level-two optimization
results in global optimization, as shown below:
$ pgf95 –O2 prog.f
Specifying –O on the command-line without a level designation is equivalent to –O2. The default
optimization level changes depending on which options you select on the command line. For
example, when you select the –g debugging option, the default optimization level is set to levelzero (–O0). However, you can override this default by placing –Olevel option after –g on the
command-line if you need to debug optimized code. Refer to Section 2.8, Default Optimization
Levels, for a description of the default levels. Optimization & Parallelization 39
As noted above, the –fast option includes –O2 on all x86 and x64 targets. If you wish to override
this with –O3 while maintaining all other elements of –fast, simply compile as follows:
$ pgf95 -fast –O3 prog.f
2.3.1 Scalar SSE Code Generation
For all processors prior to Intel Pentium 4 and AMD Opteron/Athlon64, for example Intel
Pentium III and AMD AthlonXP/MP processors, scalar floating-point arithmetic as generated by
the PGI Workstation compilers is performed using x87 floating-point stack instructions. With the
advent of SSE/SSE2 instructions on Intel Pentium 4/Xeon and AMD Opteron/Athlon64, it is
possible to perform all scalar floating-point arithmetic using SSE/SSE2 instructions. In most
cases, this is beneficial from a performance standpoint.
The default on 32-bit Intel Pentium II/III (–tp p6, –tp piii, etc) or AMD AthlonXP/MP (–tp k7) is
to use x87 instructions for scalar floating-point arithmetic. The default on Intel Pentium 4/Xeon
or Intel EM64T running a 32-bit operating system (–tp p7), AMD Opteron/Athlon64 running a
32-bit operating system (–tp k8-32), or AMD Opteron/Athlon64 or Intel EM64T processors
running a 64-bit operating system (–tp k8-64 and –tp p7-64 respectively) is to use SSE/SSE2
instructions for scalar floating-point arithmetic. The only way to override this default on AMD
Opteron/Athlon64 or Intel EM64T processors running a 64-bit operating system is to specify an
older 32-bit target (for example –tp k7 or –tp piii).
Note that there can be significant arithmetic differences between calculations performed using
x87 instructions versus SSE/SSE2. By default, all floating-point data is promoted to IEEE 80-bit
format when stored on the x87 floating-point stack, and all x87 operations are performed registerto-register in this same format. Values are converted back to IEEE 32-bit or IEEE 64-bit when
stored back to memory (for REAL/float and DOUBLE PRECISION/double data respectively).
The default precision of the x87 floating-point stack can be reduced to IEEE 32-bit or IEEE 64-bit
globally by compiling the main program with the –pc {32 | 64} option to the PGI Workstation
compilers, which is described in detail in Chapter 3, Command Line Options. However, there is
no way to ensure that operations performed in mixed precision will match those produced on a
traditional load-store RISC/UNIX system which implements IEEE 64-bit and IEEE 32-bit
registers and associated floating-point arithmetic instructions.
In contrast, arithmetic results produced on Intel Pentium 4/Xeon, AMD Opteron/Athlon64 or Intel
EM64T processors will usually closely match or be identical to those produced on a traditional
RISC/UNIX system if all scalar arithmetic is performed using SSE/SSE2 instructions. You
should keep this in mind when porting applications to and from systems which support both x87
and full SSE/SSE2 floating-point arithmetic. Many subtle issues can arise which affect your
numerical results, sometimes to several digits of accuracy. 40 Chapter 2
2.4 Loop Unrolling using -Munroll
This optimization unrolls loops, executing multiple instances of the loop during each iteration.
This reduces branch overhead, and can improve execution speed by creating better opportunities
for instruction scheduling. A loop with a constant count may be completely unrolled or partially
unrolled. A loop with a non-constant count may also be unrolled. A candidate loop must be an
innermost loop containing one to four blocks of code. The following shows the use of the
–Munroll option:
$ pgf95 –Munroll prog.f
The –Munroll option is included as part of –fast and –fastsse on all x86 and x64 targets. The loop
unroller expands the contents of a loop and reduces the number of times a loop is executed.
Branching overhead is reduced when a loop is unrolled two or more times, since each iteration of
the unrolled loop corresponds to two or more iterations of the original loop; the number of branch
instructions executed is proportionately reduced. When a loop is unrolled completely, the loop’s
branch overhead is eliminated altogether.
Loop unrolling may be beneficial for the instruction scheduler. When a loop is completely
unrolled or unrolled two or more times, opportunities for improved scheduling may be presented.
The code generator can take advantage of more possibilities for instruction grouping or filling
instruction delays found within the loop. Examples 2-1 and 2-2 show the effect of code unrolling
on a segment that computes a dot product.
REAL*4 A(100), B(100), Z
INTEGER I
DO I=1, 100
Z = Z + A(i) * B(i)
END DO
END
Example 2-1: Dot Product Code
REAL*4 A(100), B(100), Z
INTEGER I
DO I=1, 100, 2
Z = Z + A(i) * B(i)
Z = Z + A(i+1) * B(i+1)
END DO
END
Example 2-2: Unrolled Dot Product Code Optimization & Parallelization 41
Using the –Minfo option, the compiler informs you when a loop is being unrolled. For example, a
message indicating the line number, and the number of times the code is unrolled, similar to the
following will display when a loop is unrolled:
dot:
5, Loop unrolled 5 times
Using the c: and n: sub-options to –Munroll, or using –Mnounroll, you can control
whether and how loops are unrolled on a file-by-file basis. Using directives or pragmas as
specified in Chapter 7, Optimization Directives and Pragmas, you can precisely control whether
and how a given loop is unrolled. See Chapter 3, Command Line Options, for a detailed
description of the –Munroll option.
2.5 Vectorization using -Mvect
The –Mvect option is included as part of –fastsse on all x86 and x64 targets. If your program
contains computationally intensive loops, the –Mvect option may be helpful. If in addition you
specify –Minfo, and your code contains loops that can be vectorized, the compiler reports
relevant information on the optimizations applied.
When a PGI compiler command is invoked with the –Mvect option, the vectorizer scans code
searching for loops that are candidates for high-level transformations such as loop distribution,
loop interchange, cache tiling, and idiom recognition (replacement of a recognizable code
sequence, such as a reduction loop, with optimized code sequences or function calls). When the
vectorizer finds vectorization opportunities, it internally rearranges or replaces sections of loops
(the vectorizer changes the code generated; your source code’s loops are not altered). In addition
to performing these loop transformations, the vectorizer produces extensive data dependence
information for use by other phases of compilation and detects opportunities to use vector or
packed Streaming SIMD Extensions (SSE) instructions on processors where these are supported.
The –Mvect option can speed up code which contains well-behaved countable loops which
operate on large REAL, REAL*4, REAL*8, INTEGER*4, COMPLEX or COMPLEX DOUBLE arrays in
Fortran and their C/C++ counterparts. However, it is possible that some codes will show a
decrease in performance when compiled with –Mvect due to the generation of conditionally
executed code segments, inability to determine data alignment, and other code generation factors.
For this reason, it is recommended that you check carefully whether particular program units or
loops show improved performance when compiled with this option enabled.
2.5.1 Vectorization Sub-options
The vectorizer performs high-level loop transformations on countable loops. A loop is countable
if the number of iterations is set only before loop execution and cannot be modified during loop 42 Chapter 2
execution. Some of the vectorizer transformations can be controlled by arguments to the –Mvect
command line option. The following sections describe the arguments that affect the operation of
the vectorizer. In addition, some of these vectorizer operations can be controlled from within code
using directives and pragmas. For details on the use of directives and pragmas, refer to Chapter 7,
Optimization Directives and Pragmas.
The vectorizer performs the following operations:
• Loop interchange
• Loop splitting
• Loop fusion
• Memory-hierarchy (cache tiling) optimizations
• Generation of SSE instructions on processors where these are supported
• Generation of prefetch instructions on processors where these are supported
• Loop iteration peeling to maximize vector alignment
• Alternate code generation
By default, –Mvect without any sub-options is equivalent to:
–Mvect=assoc,cachesize:262144
This enables the options for nested loop transformation and various other vectorizer options.
These defaults may vary depending on the target system.
2.5.1.1 Assoc Option
The option –Mvect=assoc instructs the vectorizer to perform associativity conversions that can
change the results of a computation due to roundoff error (–Mvect=noassoc disables this option).
For example, a typical optimization is to change one arithmetic operation to another arithmetic
operation that is mathematically correct, but can be computationally different and generate faster
code. This option is provided to enable or disable this transformation, since roundoff error for
such associativity conversions may produce unacceptable results.
2.5.1.2 Cachesize Option
The option –Mvect=cachesize:n instructs the vectorizer to tile nested loop operations assuming a
data cache size of n bytes. By default, the vectorizer attempts to tile nested loop operations, such Optimization & Parallelization 43
as matrix multiply, using multi-dimensional strip-mining techniques to maximize re-use of items
in the data cache.
2.5.1.3 SSE Option
The option –Mvect=sse instructs the vectorizer to automatically generate packed SSE, SSE2
(streaming SIMD extensions) and prefetch instructions when vectorizable loops are encountered.
SSE instructions, first introduced on Pentium III and AthlonXP processors, operate on singleprecision floating-point data, and hence apply only to vectorizable loops that operate on singleprecision floating-point data. SSE2 instructions, first introduced on Pentium 4, Xeon and Opteron
processors, operate on double-precision floating-point data. Prefetch instructions, first introduced
on Pentium III and AthlonXP processors, can be used to improve the performance of vectorizable
loops that operate on either 32-bit or 64-bit floating-point data. See table P-2 for a concise list of
processors that support SSE, SSE2 and prefetch instructions.
Note: Programs units compiled with –Mvect=sse will not execute on Pentium, Pentium
Pro, Pentium II or first generation AMD Athlon processors. They will only execute
correctly on Pentium III, Pentium 4, Xeon, EM64T, AthlonXP, Athlon64 and Opteron
systems running an SSE-enabled operating system.
2.5.1.4 Prefetch Option
The option –Mvect=prefetch instructs the vectorizer to automatically generate prefetch
instructions when vectorizable loops are encountered, even in cases where SSE or SSE2
instructions are not generated. Usually, explicit prefetching is not necessary on Pentium 4, Xeon
and Opteron because these processors support hardware prefetching; nonetheless, it sometimes
can be worthwhile to experiment with explicit prefetching. Prefetching can be controlled on a
loop-by-loop level using prefetch directives, which are described in detail in section 7.7, Prefetch
Directives.
Note: Program units compiled with –Mvect=prefetch will not execute correctly on
Pentium, Pentium Pro, or Pentium II processors. They will execute correctly only on
Pentium III, Pentium 4, Xeon, EM64T, AthlonXP, Athlon64 or Opteron systems. In
addition, the prefetchw instruction is only supported on AthlonXP, Athlon64 or
Opteron systems and can cause instruction faults on non-AMD processors. For this
reason, the PGI compilers do not generate prefetchw instructions by default on any
target.
In addition to these sub-options to –Mvect, several other sub-options are supported. See the
description of –Mvect in Chapter 3, Command Line Options, for a detailed description of all
available sub-options. 44 Chapter 2
2.5.2 Vectorization Example Using SSE/SSE2 Instructions
One of the most important vectorization options is –Mvect=sse. This section contains an example
of the use and potential effects of –Mvect=sse.
When the compiler switch –Mvect=sse is used, the vectorizer in the PGI Workstation compilers
automatically uses SSE and SSE2 instructions where possible when targeting processors where
these are supported. This capability is supported by all of the PGI Fortran, C and C++ compilers.
See table P-2 for a complete specification of which x86 and x64 processors support SSE and SSE2
instructions. Using –Mvect=sse, performance improvements of up to two times over equivalent
scalar code sequences are possible.
In the program in example 2-3, the vectorizer recognizes the vector operation in subroutine 'loop'
when the compiler switch –Mvect=sse is used. This example shows the compilation,
informational messages, and runtime results using the SSE instructions on an AMD Opteron
processor-based system, along with issues that affect SSE performance.
First note that the arrays in Example 2-3 are single-precision and that the vector operation is done
using a unit stride loop. Thus, this loop can potentially be vectorized using SSE instructions on
any processor that supports SSE or SSE2 instructions. SSE operations can be used to operate on
pairs of single-precision floating-point numbers, and do not apply to double-precision
floating-point numbers. SSE2 instructions can be used to operate on quads of single-precision
floating-point numbers or on pairs of double-precision floating-point numbers.
Loops vectorized using SSE or SSE2 instructions operate much more efficiently when processing
vectors that are aligned to a cache-line boundary. You can cause unconstrained data objects of
size 16 bytes or greater to be cache-aligned by compiling with the –Mcache_align switch. An
unconstrained data object is a data object that is not a common block member and not a member
of an aggregate data structure.
Note: In order for stack-based local variables to be properly aligned, the main program
or function must be compiled with –Mcache_align.
The –Mcache_align switch has no effect on the alignment of Fortran allocatable or automatic
arrays. If you have arrays that are constrained, for example vectors that are members of Fortran
common blocks, you must specifically pad your data structures to ensure proper cache alignment;
–Mcache_align causes only the beginning address of each common block to be cache-aligned.
The following examples show results of compiling the example code with and without
–Mvect=sse. Optimization & Parallelization 45
program vector_op
parameter (N = 9999)
real*4 x(n),y(n),z(n),w(n)
do i = 1,n
y(i) = i
z(i) = 2*i
w(i) = 4*i
enddo
do j = 1, 200000
call loop(x,y,z,w,1.0e0,n)
enddo
print*,x(1),x(771),x(3618),x(6498),x(9999)
end
subroutine loop(a,b,c,d,s,n)
integer i,n
real*4 a(n),b(n),c(n),d(n),s
do i = 1,n
a(i) = b(i) + c(i) – s * d(i)
enddo
end
Example 2-3: Vector operation using SSE instructions
Assume the above program is compiled as follows:
% pgf95 -fast -Minfo vadd.f
vector_op:
4, Loop unrolled 4 times
loop:
18, Loop unrolled 4 times
Following is the result if the generated executable is run and timed on a standalone AMD Opteron
2.2 Ghz system:
% /bin/time a.out
-1.000000 -771.000 -3618.000 -6498.00 -9999.00
5.15user 0.00system 0:05.16 elapsed 99%CPU 46 Chapter 2
Now, recompile with SSE vectorization enabled:
% pgf95 -fast –Mvect=sse -Minfo vadd.f
vector_op:
4, Unrolling inner loop 8 times
Loop unrolled 7 times (completely unrolled)
loop:
18, Generating vector sse code for inner loop
Generated 3 prefetch instructions for this loop
Note the informational message indicating that the loop has been vectorized and SSE instructions
have been generated. The second part of the informational message notes that prefetch
instructions have been generated for 3 loads to minimize latency of transfers of data from main
memory.
Executing again, you should see results similar to the following:
% /bin/time a.out
-1.000000 -771.000 -3618.00 -6498.00 -9999.0
3.55user 0.00system 0:03.56elapsed 99%CPU
The result is a speed-up of 45% over the equivalent scalar (i.e. non-SSE) version of the program.
Speed-up realized by a given loop or program can vary widely based on a number of factors:
• Performance improvement using vector SSE or SSE2 instructions is most effective when the
vectors of data are resident in the data cache.
• If data is aligned properly, performance will be better in general than when using vector SSE
operations on unaligned data.
• If the compiler can guarantee that data is aligned properly, even more efficient sequences of
SSE instructions can be generated.
• SSE2 vector instructions can operate on 4 single-precision elements concurrently, but only 2
double-precision elements. As a result, the efficiency of loops that operate on singleprecision data can be higher.
Note: Compiling with –Mvect=sse can result in numerical differences from the
generated executable. Certain vectorizable operations, for example dot products, are
sensitive to order of operations and the associative transformations necessary to enable
vectorization (or parallelization). Optimization & Parallelization 47
2.6 Auto-Parallelization using -Mconcur
With the -Mconcur option the compiler scans code searching for loops that are candidates for
auto-parallelization. –Mconcur must be used at both compile-time and link-time. When the
parallelizer finds opportunities for auto-parallelization, it parallelizes loops and you are informed
of the line or loop being parallelized if the -Minfo option is present on the compile line. See
Chapter 3, Command Line Options, for a complete specification of -Mconcur.
A loop is considered parallelizable if doesn't contain any cross-iteration data dependencies. Crossiteration dependencies from reductions and expandable scalars are excluded from consideration,
enabling more loops to be parallelizable. In general, loops with calls are not parallelized due to
unknown side effects. Also, loops with low trip counts are not parallelized since the overhead in
setting up and starting a parallel loop will likely outweigh the potential benefits. In addition, the
default is to not parallelize innermost loops, since these often by definition are vectorizable using
SSE instructions and it is seldom profitable to both vectorize and parallelize the same loop,
especially on multi-core processors. Compiler switches and directives are available to let you
override most of these restrictions on auto-parallelization.
2.6.1 Auto-parallelization Sub-options
The parallelizer performs various operations that can be controlled by arguments to the –Mconcur
command line option. The following sections describe these arguments that affect the operation of
the vectorizer. In addition, these vectorizer operations can be controlled from within code using
directives and pragmas. For details on the use of directives and pragmas, refer to Chapter 7,
Optimization Directives and Pragmas.
By default, –Mconcur without any sub-options is equivalent to:
–Mconcur=dist:block
This enables parallelization of loops with blocked iteration allocation across the available threads
of execution. These defaults may vary depending on the target system.
2.6.1.1 Altcode Option
The option –Mconcur=altcode instructs the parallelizer to generate alternate serial code for
parallelized loops. If altcode is specified without arguments, the parallelizer determines an
appropriate cutoff length and generates serial code to be executed whenever the loop count is less
than or equal to that length. If altcode:n is specified, the serial altcode is executed whenever the
loop count is less than or equal to n. If noaltcode is specified, no alternate serial code is
generated. 48 Chapter 2
2.6.1.2 Dist Option
The option –Mconcur=dist:{block|cyclic} option specifies whether to assign loop iterations to the
available threads in blocks or in a cyclic (round-robin) fashion. Block distribution is the default.
If cyclic is specified, iterations are allocated to processors cyclically. That is, processor 0
performs iterations 0, 3, 6, etc.; processor 1 performs iterations 1, 4, 7, etc.; and processor 2
performs iterations 2, 5, 8, etc.
2.6.1.3 Cncall Option
The option –Mconcur=cncall specifies that it is safe to parallelize loops that contain subroutine or
function calls. By default, such loops are excluded from consideration for auto-parallelization.
Also, no minimum loop count threshold must be satisfied before parallelization will occur, and
last values of scalars are assumed to be safe.
The environment variable NCPUS is checked at runtime for a parallel program. If NCPUS is set to
1, a parallel program runs serially, but will use the parallel routines generated during compilation.
If NCPUS is set to a value greater than 1, the specified number of processors will be used to
execute the program. Setting NCPUS to a value exceeding the number of physical processors can
produce inefficient execution. Executing a program on multiple processors in an environment
where some of the processors are being time-shared with another executing job can also result in
inefficient execution.
As with the vectorizer, the -Mconcur option can speed up code if it contains well-behaved
countable loops and/or computationally intensive nested loops that operate on arrays. However, it
is possible that some codes will show a decrease in performance on multi-processor systems when
compiled with -Mconcur due to parallelization overheads, memory bandwidth limitations in the
target system, false-sharing of cache lines, or other architectural or code-generation factors. For
this reason, it is recommended that you check carefully whether particular program units or loops
show improved performance when compiled using this option.
If the compiler is not able to successfully auto-parallelize your application, you should refer to
Chapter 5, OpenMP Directives for Fortran, or Chapter 6, OpenMP Pragmas for C and C++, to
see if insertion of explicit parallelization directives or pragmas and use of the –mp compiler
option enables the application to run in parallel.
2.6.2 Loops That Fail to Parallelize
In spite of the sophisticated analysis and transformations performed by the compiler,
programmers will often note loops that are seemingly parallel, but are not parallelized. In this
subsection, we’ll look at some examples of common situations where parallelization does not
occur. Optimization & Parallelization 49
2.6.2.1 Innermost Loops
As noted earlier in this chapter, the PGI compilers will not parallelize innermost loops by default,
because it is usually not profitable. You can override this default using the command-line option
–Mconcur=innermost.
2.6.2.2 Timing Loops
Often, loops will occur in programs that are similar to timing loops. The outer loop in the
following example is one such loop.
do 1 j = 1, 2
do 1 i = 1, n
a(i) = b(i) + c(i)
1 continue
The outer loop above is not parallelized because the compiler detects a cross-iteration dependence
in the assignment to a(i). Suppose the outer loop were parallelized. Then both processors would
simultaneously attempt to make assignments into a(1:n). Now in general the values computed by
each processor for a(1:n) will differ, so that simultaneous assignment into a(1:n) will produce
values different from sequential execution of the loops.
In this example, values computed for a(1:n) don’t depend on j, so that simultaneous assignment
by both processors will not yield incorrect results. However, it is beyond the scope of the
compilers’ dependence analysis to determine that values computed in one iteration of a loop don’t
differ from values computed in another iteration. So the worst case is assumed, and different
iterations of the outer loop are assumed to compute different values for a(1:n). Is this
assumption too pessimistic? If j doesn’t occur anywhere within a loop, the loop exists only to
cause some delay, most probably to improve timing resolution. And, it’s not usually valid to
parallelize timing loops; to do so would distort the timing information for the inner loops.
2.6.2.3 Scalars
Quite often, scalars will inhibit parallelization of non-innermost loops. There are two separate
cases that present problems. In the first case, scalars appear to be expandable, but appear in noninnermost loops, as in the following example.
do 1 j = 1, n
x = b(j)
do 1 i = 1, n
a(i,j) = x + c(i,j)
1 continue 50 Chapter 2
There are a number of technical problems to be resolved in order to recognize expandable scalars
in non-innermost loops. Until this generalization occurs, scalars like x above will inhibit
parallelization of loops in which they are assigned. In the following example, scalar k is not
expandable, and it is not an accumulator for a reduction.
k = 1
do 3 i = 1, n
do 1 j = 1, n
1 a(j,i) = b(k) * x
k = i
2 if (i .gt. n/2) k = n - (i - n/2)
3 continue
If the outer loop is parallelized, conflicting values will be stored into k by the various processors.
The variable k cannot be made local to each processor because the value of k must remain
coherent among the processors. It is possible the loop could be parallelized if all assignments to k
are placed in critical sections. However, it is not clear where critical sections should be introduced
because in general the value for k could depend on another scalar (or on k itself), and code to
obtain the value of other scalars must reside in the same critical section.
In the example above, the assignment to k within a conditional at label 2 prevents k from being
recognized as an induction variable. If the conditional statement at label 2 is removed, k would be
an induction variable whose value varies linearly with j, and the loop could be parallelized.
2.6.2.4 Scalar Last Values
During parallelization, scalars within loops often need to be privatized; that is, each execution
thread will have its own independent copy of the scalar. Problems can arise if a privatized scalar
is accessed outside the loop. For example, consider the following loop:
for (i = 1; i 5.0 ) t = x[i];
}
v = t;
The value of t may not be computed on the last iteration of the loop. Normally, if a scalar is
assigned within a loop and used following the loop, the PGI compilers save the last value of the
scalar. However, if the loop is parallelized and the scalar is not assigned on every iteration, it may
be difficult (without resorting to costly critical sections) to determine on what iteration t is last
assigned. Analysis allows the compiler to determine that a scalar is assigned on each iteration and
hence that the loop is safe to parallelize if the scalar is used later. Optimization & Parallelization 51
For example:
for ( i = 1; i < n; i++){
if ( x[i] > 0.0 ) {
t = 2.0;
}
else {
t = 3.0;
y[i] = ...t;
}
}
v = t
where t is assigned on every iteration of the loop. However, there are cases where a scalar may be
privatizable, but if it is used after the loop, it is unsafe to parallelize. Examine this loop:
for ( i = 1; i < N; i++ ){
if( x[i] > 0.0 ){
t = x[i];
...
...
y[i] = ...t;
}
}
v = t;
where each use of t within the loop is reached by a definition from the same iteration. Here t is
privatizable, but the use of t outside the loop may yield incorrect results since the compiler may
not be able to detect on which iteration of the parallelized loop t is last assigned. The compiler
detects the above cases. Where a scalar is used after the loop but is not defined on every iteration
of the loop, parallelization will not occur.
When the programmer knows that the scalar is assigned on the last iteration of the loop, the
programmer may use a directive or pragma to let the compiler know the loop is safe to parallelize.
The Fortran directive which tells the compiler that for a given loop the last value computed for all
scalars make it safe to parallelize the loop is:
cpgi$l safe_lastval
In addition, a command-line option, –Msafe_lastval, provides this information for all loops within
the routines being compiled (essentially providing global scope). 52 Chapter 2
2.7 Inter-Procedural Analysis and Optimization using –Mipa
The PGI Fortran, C and C++ compilers use interprocedural analysis (IPA) that results in minimal
changes to makefiles and the standard edit-build-run application development cycle. Other than
adding –Mipa to the command line, no other changes are required. For reference and background,
the process of building a program without IPA is described below, followed by the minor
modifications required to use IPA with the PGI compilers. While the PGCC compiler is used here
to show how IPA works, similar capabilities apply to each of the PGI Fortran, C and C++
compilers.
2.7.1 Building a Program Without IPA – Single Step
Using the PGCC command-level C compiler driver, three (for example) source files can be
compiled and linked into a single executable with one command:
% pgcc –o a.out file1.c file2.c file3.c
In actuality, the pgcc driver executes several steps to produce the assembly code and object files
corresponding to each source file, and subsequently to link the object files together into a single
executable file. Thus, the command above is roughly equivalent to the following commands
performed individually:
% pgcc -S -o file1.s file1.c
% as -o file1.o file1.s
% pgcc -S -o file2.s file2.c
% as -o file2.o file2.s
% pgcc -S -o file3.s file3.c
% as -o file3.o file3.s
% pgcc -o a.out file1.o file2.o file3.o
If any of the three source files is edited, the executable can be rebuilt with the same command
line:
% pgcc -o a.out file1.c file2.c file3.c
This always works as intended, but has the side-effect of recompiling all of the source files, even
if only one has changed. For applications with a large number of source files, this can be timeconsuming and inefficient.
2.7.2 Building a Program Without IPA - Several Steps
It is also possible to use individual pgcc commands to compile each source file into a
corresponding object file, and one to link the resulting object files into an executable: Optimization & Parallelization 53
% pgcc -c file1.c
% pgcc -c file2.c
% pgcc -c file3.c
% pgcc -o a.out file1.o file2.o file3.o
The pgcc driver invokes the compiler and assembler as required to process each source file, and
invokes the linker for the final link command. If you modify one of the source files, the
executable can be rebuilt by compiling just that file and then relinking:
% pgcc -c file1.c
% pgcc -o a.out file1.o file2.o file3.o
2.7.3 Building a Program Without IPA Using Make
The program compilation and linking process can be simplified greatly using the make utility on
systems where it is supported. Using a file makefile containing the following lines:
a.out: file1.o file2.o file3.o
pgcc $(OPT) -o a.out file1.o file2.o file3.o
file1.o: file1.c
pgcc $(OPT) -c file1.c
file2.o: file2.c
pgcc $(OPT) -c file2.c
file3.o: file3.c
pgcc $(OPT) -c file3.c
It is possible to type a single make command:
% make
The make utility determines which object files are out of date with respect to their corresponding
source files, and invokes pgcc to recompile only those source files and to relink the executable.
If you subsequently edit one or more source files, the executable can be rebuilt with the minimum
number of recompilations using the same single make command.
2.7.4 Building a Program with IPA
Interprocedural analysis and optimization (IPA) by the PGI compilers is designed to alter the
standard and make utility command-level interfaces outlined above as little as possible. IPA
occurs in three phases: 54 Chapter 2
• Collection: Create a summary of each function or procedure, collecting the useful
information for interprocedural optimizations. This is done during the compile step if the
–Mipa switch is present on the command line; summary information is collected and
stored in the object file.
• Propagation: Processing all the object files to propagate the interprocedural summary
information across function and file boundaries. This is done during the link step, when
all the object files are combined, if the –Mipa switch is present on the link command
line.
• Recompile/Optimization: Each of the object files is recompiled with the propagated
interprocedural information, producing a specialized object file. This is also done during
the link step when the –Mipa switch is present on the link command line.
When linking with –Mipa, the PGI compilers automatically regenerate IPA-optimized versions of
each object file, essentially recompiling each file. If there are IPA-optimized objects from a
previous build, the compilers will minimize the recompile time by reusing those objects if they
are still valid. They will still be valid if the IPA-optimized object is newer than the original object
file, and the propagated IPA information for that file has not changed since it was optimized.
After each object file has been recompiled, the regular linker is invoked to build the application
with the IPA-optimized object files. The IPA-optimized object files are saved in the same
directory as the original object files, for use in subsequent program builds.
2.7.5 Building a Program with IPA - Single Step
By adding the –Mipa command line switch, several source files can be compiled and linked with
interprocedural optimizations with one command:
% pgcc -Mipa=fast -o a.out file1.c file2.c file3.c
Just like compiling without –Mipa, the driver executes several steps to produce the assembly and
object files, to create the executable:
% pgcc -Mipa=fast -S -o file1.s file1.c
% as -o file1.o file1.s
% pgcc -Mipa=fast -S -o file2.s file2.c
% as -o file2.o file2.s
% pgcc -Mipa=fast -S -o file3.s file3.c
% as -o file3.o file3.s
% pgcc -Mipa=fast -o a.out file1.o file2.o file3.o Optimization & Parallelization 55
In the last step, an IPA linker is invoked to read all the IPA summary information and perform the
interprocedural propagation. The IPA linker reinvokes the compiler on each of the object files to
recompile them with interprocedural information. This creates three new objects with mangled
names:
file1_ipa5_a.out.o, file2_ipa5_a.out.o, file2_ipa5_a.out.o
The system linker is then invoked to link these IPA-optimized objects into the final executable.
Later, if one of the three source files is edited, the executable can be rebuilt with the same
command line:
% pgcc -Mipa=fast -o a.out file1.c file2.c file3.c
This will work, but again has the side-effect of compiling each source file, and recompiling each
object file at link time.
2.7.6 Building a Program with IPA - Several Steps
Just by adding the –Mipa command-line switch, it is possible to use individual pgcc commands
to compile each source file, followed by a command to link the resulting object files into an
executable:
% pgcc -Mipa=fast -c file1.c
% pgcc -Mipa=fast -c file2.c
% pgcc -Mipa=fast -c file3.c
% pgcc -Mipa=fast -o a.out file1.o file2.o file3.o
The pgcc driver invokes the compiler and assembler as required to process each source file, and
invokes the IPA linker for the final link command. If you modify one of the source files, the
executable can be rebuilt by compiling just that file and then relinking:
% pgcc -c file1.c
% pgcc -o a.out file1.o file2.o file3.o
When the IPA linker is invoked, it will determine that the IPA-optimized object for file1.o
(file1_ipa5_a.out.o) is stale, since it is older than the object file1.o, and hence will need to be
rebuilt, and will reinvoke the compiler to generate it. In addition, depending on the nature of the
changes to the source file file1.c, the interprocedural optimizations previously performed for file2
and file3 may now be inaccurate. For instance, IPA may have propagated a constant argument
value in a call from a function in file1.c to a function in file2.c; if the value of the argument has
changed, any optimizations based on that constant value are invalid. The IPA linker will
determine which, if any, of any previously created IPA-optimized objects need to be regenerated,
and will reinvoke the compiler as appropriate to regenerate them. Only those objects that are stale 56 Chapter 2
or which have new or different IPA information will be regenerated, which saves on compile
time.
2.7.7 Building a Program with IPA Using Make
As in the previous two sections, programs can be built with IPA using the make utility, just by
adding the –Mipa command-line switch:
OPT=-Mipa=fast
a.out: file1.o file2.o file3.o
pgcc $(OPT) -o a.out file1.o file2.o file3.o
file1.o: file1.c
pgcc $(OPT) -c file1.c
file2.o: file2.c
pgcc $(OPT) -c file2.c
file3.o: file3.c
pgcc $(OPT) -c file3.c
The single command:
% make
will invoke the compiler to generate any object files that are out-of-date, then invoke pgcc to link
the objects into the executable; at link time, pgcc will call the IPA linker to regenerate any stale
or invalid IPA-optimized objects.
2.7.8 Questions about IPA
• Why is the object file so large?
An object file created with –Mipa contains several additional sections. One is the summary
information used to drive the interprocedural analysis. In addition, the object file contains
the compiler internal representation of the source file, so the file can be recompiled at link
time with interprocedural optimizations. There may be additional information when inlining
is enabled. The total size of the object file may be 5-10 times its original size. The extra
sections are not added to the final executable.
• What if I compile with –Mipa and link without –Mipa?
The PGI compilers generate a legal object file, even when the source file is compiled with
–Mipa. If you compile with –Mipa and link without –Mipa, the linker is invoked on the
original object files. A legal executable will be generated; while this will not have the
benefit of interprocedural optimizations, any other optimizations will apply.
• What if I compile without –Mipa and link with –Mipa? Optimization & Parallelization 57
At link time, the IPA linker must have summary information about all the functions or
routines used in the program. This information is created only when a file is compiled with
–Mipa. If you compile a file without –Mipa and then try to get interprocedural optimizations
by linking with –Mipa, the IPA linker will issue a message that some routines have no IPA
summary information, and will proceed to run the system linker using the original object
files. If some files were compiled with –Mipa and others were not, it will determine the
safest approximation of the IPA summary information for those files not compiled with
–Mipa, and use that to recompile the other files using interprocedural optimizations.
• Can I build multiple applications in the same directory with –Mipa?
Yes. Suppose you have three source files: main1.c, main2.c, sub.c, where sub.c is shared
between the two applications. When you build the first application with –Mipa:
% pgcc -o app1 main1.c sub.c
the IPA linker will create two IPA-optimized object files:
main1_ipa4_app1.oo sub_ipa4_app1.oo
and use them to build the first application. When you build the second application:
% pgcc -o app2 main2.c sub.c
the IPA linker will create two more IPA-optimized object files:
main2_ipa4_app2.oo sub_ipa4_app2.oo
Note there are now three object files for sub.c: the original sub.o, and two IPA-optimized
objects, one for each application in which it appears.
• How is the mangled name for the IPA-optimized object files generated?
The mangled name has '_ipa' appended, followed by the decimal number of the length of
the executable file name, followed by an underscore and the executable file name itself. The
suffix is changed to .oo so linking *.o does not pull in the IPA-optimized objects. If the
IPA linker determines that the file would not benefit from any interprocedural optimizations,
it does not have to recompile the file at link time, and will use the original object. 58 Chapter 2
2.8 Profile-Feedback Optimization using –Mpfi/–Mpfo
The PGI compilers support many common profile-feedback optimizations, including semiinvariant value optimizations and block placement. These are performed under control of the
–Mpfi/–Mpfo command-line options.
When invoked with the –Mpfi option, the PGI compilers instrument the generated executable for
collection of profile and data feedback information. This information can be used in subsequent
compilations that include the –Mpfo optimization option. –Mpfi must be used at both compiletime and link-time. Programs compiled with –Mpfi include extra code to collect run-time
statistics and write them out to a trace file. When the resulting program is executed, a profile
feedback trace file pgfi.out is generated in the current working directory.
Note: programs compiled and linked with –Mpfi will execute more slowly
due to the instrumentation and data collection overhead. You should use
executables compiled with –Mpfi only for execution of training runs.
When invoked with the –Mpfo option, the PGI compilers use data from a pgfi.out profile
feedback tracefile to enable or enhance certain performance optimizations. Use of this option
requires the presence of a pgfi.out trace file in the current working directory.
2.9 Default Optimization Levels
Table 2-1 shows the interaction between the –O, –g and –M options. In the table, level can
be 0, 1, 2 or 3, and can be vect, unroll or ipa. The default optimization level is dependent
upon these command-line options.
Table 2-1: Optimization and –O, –g and –M Options
Optimize
Option
Debug
Option
–M
Option
Optimization Level
none none none 1
none none –M 2
none –g none 0
–O none or –g none 2
–Olevel none or –g none level
–Olevel <= 2 none or –g –M 2
–O3 none or –g none 3 Optimization & Parallelization 59
Unoptimized code compiled using the option –O0 can be significantly slower than code generated
at other optimization levels. The –M option, where is vect, concur, unroll or ipa,
sets the optimization level to level-2 if no –O options are supplied. The –fast and –fastsse options
set the optimization level to a target-dependent optimization level if no –O options are supplied.
2.10 Local Optimization Using Directives and Pragmas
Command-line options let you specify optimizations for an entire source file. Directives supplied
within a Fortran source file, and pragmas supplied within a C or C++ source file, provide
information to the compiler and alter the effects of certain command-line options or default
behavior of the compiler (many directives have a corresponding command-line option).
While a command line option affects the entire source file that is being compiled, directives and
pragmas let you do the following:
• Apply, or disable, the effects of a particular command-line option to selected
subprograms or to selected loops in the source file (for example, an optimization).
• Globally override command-line options.
• Tune selected routines or loops based on your knowledge or on information obtained
through profiling.
Chapter 7, Optimization Directives and Pragmas, provides details on how to add directives and
pragmas to your source files.
2.11 Execution Timing and Instruction Counting
As this chapter shows, once you have a program that compiles, executes and gives correct results,
you may optimize your code for execution efficiency. Selecting the correct optimization level
requires some thought and may require that you compare several optimization levels before
arriving at the best solution. To compare optimization levels, you need to measure the execution
time for your program. There are several approaches you can take for timing execution. You can
use shell commands that provide execution time statistics, you can include function calls in your
code that provides timing information, or you can profile sections of code. Timing functions
available with the PGI compilers include 3F timing routines, the SECNDS pre-declared function in
PGF77 or PGF95, or the SYSTEM_CLOCK or CPU_CLOCK intrinsics in PGF95 or PGHPF. In general,
when timing a program one should try to eliminate or reduce the amount of system level activities such
as program loading, I/O and task switching.
Example 2-4 shows a fragment that indicates how to use SYSTEM_CLOCK effectively within either
an HPF or F90/F95 program unit. 60 Chapter 2
. . .
integer :: nprocs, hz, clock0, clock1
real :: time
integer, allocatable :: t(:)
!hpf$ distribute t(cyclic)
#if defined (HPF)
allocate (t(number_of_processors()))
#elif defined (_OPENMP)
allocate (t(OMP_GET_NUM_THREADS()))
#else
allocate (t(1))
#endif
call system_clock (count_rate=hz)
!
call system_clock(count=clock0)
< do work>
call system_clock(count=clock1)
!
t = (clock1 - clock0)
time = real (sum(t)) / (real(hz) * size(t))
. . .
Example 2-4: Using SYSTEM_CLOCK Command-line Options 61
Chapter 3
Command Line Options
This chapter describes the syntax and operation of each compiler option. The options are arranged
in alphabetical order. On a command-line, options need to be preceded by a hyphen (-). If the
compiler does not recognize an option, it passes the option to the linker.
This chapter uses the following notation:
[item] Square brackets indicate that the enclosed item is optional.
{item | item} Braces indicate that you must select one and only one of the enclosed
items. A vertical bar (|) separates the choices.
... Horizontal ellipses indicate that zero or more instances of the preceding
item are valid.
Note: Some options do not allow a space between the option and its argument or within an
argument. This fact is noted in the syntax section of the respective option.
Table 3-1: Generic PGI Compiler Options
Option Description
–# Display invocation information.
–### Show but do not execute the driver commands (same as
–dryrun).
–byteswapio (Fortran only) Swap bytes from big-endian to little-endian or
vice versa on input/output of unformatted data
–C Instrument the generated executable to perform array bounds
checking at runtime.
–c Stops after the assembly phase and saves the object code in
filename.o.
-cyglibs (Win32 only) link against the Cygnus libraries and use the
Cygnus include files. You must have the full Cygwin32
environment installed in order to use this switch.
–D Defines a preprocessor macro. 62 Chapter 3
Option Description
-d r y r u n Show but do not execute driver commands.
-E Stops after the preprocessing phase and displays the
preprocessed file on the standard output.
-F Stops after the preprocessing phase and saves the
preprocessed file in filename.f (this option is only valid for
the PGI Fortran compilers).
-fast Generally optimal set of flags for the target.
-fastsse Generally optimal set of flags for targets that include
SSE/SSE2 capability.
-flags Display valid driver options.
–fpic (Linux only) Generate position-independent code.
-fPIC (Linux only) Equivalent to -fpic.
-g Includes debugging information in the object module.
-g77libs (Linux only) Allow object files generated by g77 to be linked
into PGI main programs.
-gopt Includes debugging information in the object module, but
forces assembly code generation identical to that obtained
when -g is not present on the command line.
-help Display driver help message.
-I Adds a directory to the search path for #include files.
–i2 Treat INTEGER variables as 2 bytes.
–i4 Treat INTEGER variables as 4 bytes.
–i8 Treat INTEGER and LOGICAL variables as 8 bytes and use
64-bits for INTEGER*8 operations.
-K Requests special compilation semantics with regard to
conformance to IEEE 754.
-L Specifies a library directory.
–l Loads a library.
-M Selects variations for code generation and optimization.
–m Displays a link map on the standard output. Command-line Options 63
Option Description
-m c m o d e l = m e d i u m (-tp k8-64 and –tp p7-64 targets only) Generate code which
supports the medium memory model in the linux86-64
environment.
–module (F90/F95/HPF only) Save/search for module files in
directory .
-mp Interpret and process user-inserted shared-memory parallel
programming directives (see Chapters 5 and 6).
-mslibs (Win32 only) use the Microsoft linker and include files, and
link against the Microsoft Visual C++ libraries. Microsoft
Visual C++ must be installed in order to use this switch.
-msvcrt (Win32 only) use Microsoft’s msvcrt.dll at runtime
rather than the default crtdll.dll.
–O Specifies code optimization level where
