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This is libgomp.info, produced by makeinfo version 4.8 from
/scratch/mitchell/gcc-releases/gcc-4.2.2/gcc-4.2.2/libgomp/libgomp.texi.
Copyright (C) 2006 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding Free
Software", the Front-Cover texts being (a) (see below), and with the
Back-Cover Texts being (b) (see below). A copy of the license is
included in the section entitled "GNU Free Documentation License".
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.
INFO-DIR-SECTION GNU Libraries
START-INFO-DIR-ENTRY
* libgomp: (libgomp). GNU OpenMP runtime library
END-INFO-DIR-ENTRY
This manual documents the GNU implementation of the OpenMP API for
multi-platform shared-memory parallel programming in C/C++ and Fortran.
Published by the Free Software Foundation 51 Franklin Street, Fifth
Floor Boston, MA 02110-1301 USA
Copyright (C) 2006 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding Free
Software", the Front-Cover texts being (a) (see below), and with the
Back-Cover Texts being (b) (see below). A copy of the license is
included in the section entitled "GNU Free Documentation License".
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development.
File: libgomp.info, Node: Top, Next: Enabling OpenMP, Up: (dir)
Introduction
************
This manual documents the usage of libgomp, the GNU implementation of
the OpenMP (http://www.openmp.org) Application Programming Interface
(API) for multi-platform shared-memory parallel programming in C/C++
and Fortran.
* Menu:
* Enabling OpenMP:: How to enable OpenMP for your applications.
* Runtime Library Routines:: The OpenMP runtime application programming
interface.
* Environment Variables:: Influencing runtime behavior with environment
variables.
* The libgomp ABI:: Notes on the external ABI presented by libgomp.
* Reporting Bugs:: How to report bugs in GNU OpenMP.
* Copying:: GNU general public license says
how you can copy and share libgomp.
* GNU Free Documentation License::
How you can copy and share this manual.
* Funding:: How to help assure continued work for free
software.
* Index:: Index of this documentation.
File: libgomp.info, Node: Enabling OpenMP, Next: Runtime Library Routines, Prev: Top, Up: Top
1 Enabling OpenMP
*****************
To activate the OpenMP extensions for C/C++ and Fortran, the
compile-time flag `-fopenmp' must be specified. This enables the OpenMP
directive `#pragma omp' in C/C++ and `!$omp' directives in free form,
`c$omp', `*$omp' and `!$omp' directives in fixed form, `!$' conditional
compilation sentinels in free form and `c$', `*$' and `!$' sentinels in
fixed form, for Fortran. The flag also arranges for automatic linking
of the OpenMP runtime library (*Note Runtime Library Routines::).
A complete description of all OpenMP directives accepted may be
found in the OpenMP Application Program Interface
(http://www.openmp.org) manual, version 2.5.
File: libgomp.info, Node: Runtime Library Routines, Next: Environment Variables, Prev: Enabling OpenMP, Up: Top
2 Runtime Library Routines
**************************
The runtime routines described here are defined by section 3 of the
OpenMP specifications in version 2.5.
Control threads, processors and the parallel environment.
* Menu:
* omp_get_dynamic:: Dynamic teams setting
* omp_get_max_threads:: Maximum number of threads
* omp_get_nested:: Nested parallel regions
* omp_get_num_procs:: Number of processors online
* omp_get_num_threads:: Size of the active team
* omp_get_thread_num:: Current thread ID
* omp_in_parallel:: Whether a parallel region is active
* omp_set_dynamic:: Enable/disable dynamic teams
* omp_set_nested:: Enable/disable nested parallel regions
* omp_set_num_threads:: Set upper team size limit
Initialize, set, test, unset and destroy simple and nested locks.
* Menu:
* omp_init_lock:: Initialize simple lock
* omp_set_lock:: Wait for and set simple lock
* omp_test_lock:: Test and set simple lock if available
* omp_unset_lock:: Unset simple lock
* omp_destroy_lock:: Destroy simple lock
* omp_init_nest_lock:: Initialize nested lock
* omp_set_nest_lock:: Wait for and set simple lock
* omp_test_nest_lock:: Test and set nested lock if available
* omp_unset_nest_lock:: Unset nested lock
* omp_destroy_nest_lock:: Destroy nested lock
Portable, thread-based, wall clock timer.
* Menu:
* omp_get_wtick:: Get timer precision.
* omp_get_wtime:: Elapsed wall clock time.
File: libgomp.info, Node: omp_get_dynamic, Next: omp_get_max_threads, Up: Runtime Library Routines
2.1 `omp_get_dynamic' - Dynamic teams setting
=============================================
_Description_:
This function returns `true' if enabled, `false' otherwise. Here,
`true' and `false' represent their language-specific counterparts.
The dynamic team setting may be initialized at startup by the
`OMP_DYNAMIC' environment variable or at runtime using
`omp_set_dynamic'. If undefined, dynamic adjustment is disabled by
default.
_C/C++_:
_Prototype_: `int omp_get_dynamic();'
_Fortran_:
_Interface_: `logical function omp_get_dynamic()'
_See also_:
*Note omp_set_dynamic::, *Note OMP_DYNAMIC::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.8.
File: libgomp.info, Node: omp_get_max_threads, Next: omp_get_nested, Prev: omp_get_dynamic, Up: Runtime Library Routines
2.2 `omp_get_max_threads' - Maximum number of threads
=====================================================
_Description_:
Return the maximum number of threads used for parallel regions
that do not use the clause `num_threads'.
_C/C++_:
_Prototype_: `int omp_get_max_threads();'
_Fortran_:
_Interface_: `integer function omp_get_max_threads()'
_See also_:
*Note omp_set_num_threads::, *Note omp_set_dynamic::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.3.
File: libgomp.info, Node: omp_get_nested, Next: omp_get_num_procs, Prev: omp_get_max_threads, Up: Runtime Library Routines
2.3 `omp_get_nested' - Nested parallel regions
==============================================
_Description_:
This function returns `true' if nested parallel regions are
enabled, `false' otherwise. Here, `true' and `false' represent
their language-specific counterparts.
Nested parallel regions may be initialized at startup by the
`OMP_NESTED' environment variable or at runtime using
`omp_set_nested'. If undefined, nested parallel regions are
disabled by default.
_C/C++_:
_Prototype_: `int omp_get_nested();'
_Fortran_:
_Interface_: `integer function omp_get_nested()'
_See also_:
*Note omp_set_nested::, *Note OMP_NESTED::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section
3.2.10.
File: libgomp.info, Node: omp_get_num_procs, Next: omp_get_num_threads, Prev: omp_get_nested, Up: Runtime Library Routines
2.4 `omp_get_num_procs' - Number of processors online
=====================================================
_Description_:
Returns the number of processors online.
_C/C++_:
_Prototype_: `int omp_get_num_procs();'
_Fortran_:
_Interface_: `integer function omp_get_num_procs()'
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.5.
File: libgomp.info, Node: omp_get_num_threads, Next: omp_get_thread_num, Prev: omp_get_num_procs, Up: Runtime Library Routines
2.5 `omp_get_num_threads' - Size of the active team
===================================================
_Description_:
The number of threads in the current team. In a sequential section
of the program `omp_get_num_threads' returns 1.
The default team size may be initialized at startup by the
`OMP_NUM_THREADS' environment variable. At runtime, the size of
the current team may be set either by the `NUM_THREADS' clause or
by `omp_set_num_threads'. If none of the above were used to define
a specific value and `OMP_DYNAMIC' is disabled, one thread per CPU
online is used.
_C/C++_:
_Prototype_: `int omp_get_num_threads();'
_Fortran_:
_Interface_: `integer function omp_get_num_threads()'
_See also_:
*Note omp_get_max_threads::, *Note omp_set_num_threads::, *Note
OMP_NUM_THREADS::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.2.
File: libgomp.info, Node: omp_get_thread_num, Next: omp_in_parallel, Prev: omp_get_num_threads, Up: Runtime Library Routines
2.6 `omp_get_thread_num' - Current thread ID
============================================
_Description_:
Unique thread identification number. In a sequential parts of the
program, `omp_get_thread_num' always returns 0. In parallel
regions the return value varies from 0 to `omp_get_max_threads'-1
inclusive. The return value of the master thread of a team is
always 0.
_C/C++_:
_Prototype_: `int omp_get_thread_num();'
_Fortran_:
_Interface_: `integer function omp_get_thread_num()'
_See also_:
*Note omp_get_max_threads::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.4.
File: libgomp.info, Node: omp_in_parallel, Next: omp_set_dynamic, Prev: omp_get_thread_num, Up: Runtime Library Routines
2.7 `omp_in_parallel' - Whether a parallel region is active
===========================================================
_Description_:
This function returns `true' if currently running in parallel,
`false' otherwise. Here, `true' and `false' represent their
language-specific counterparts.
_C/C++_:
_Prototype_: `int omp_in_parallel();'
_Fortran_:
_Interface_: `logical function omp_in_parallel()'
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.6.
File: libgomp.info, Node: omp_set_dynamic, Next: omp_set_nested, Prev: omp_in_parallel, Up: Runtime Library Routines
2.8 `omp_set_dynamic' - Enable/disable dynamic teams
====================================================
_Description_:
Enable or disable the dynamic adjustment of the number of threads
within a team. The function takes the language-specific equivalent
of `true' and `false', where `true' enables dynamic adjustment of
team sizes and `false' disables it.
_C/C++_:
_Prototype_: `void omp_set_dynamic(int);'
_Fortran_:
_Interface_: `subroutine omp_set_dynamic(set)'
`integer, intent(in) :: set'
_See also_:
*Note OMP_DYNAMIC::, *Note omp_get_dynamic::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.7.
File: libgomp.info, Node: omp_set_nested, Next: omp_set_num_threads, Prev: omp_set_dynamic, Up: Runtime Library Routines
2.9 `omp_set_nested' - Enable/disable nested parallel regions
=============================================================
_Description_:
Enable or disable nested parallel regions, i.e., whether team
members are allowed to create new teams. The function takes the
language-specific equivalent of `true' and `false', where `true'
enables dynamic adjustment of team sizes and `false' disables it.
_C/C++_:
_Prototype_: `void omp_set_dynamic(int);'
_Fortran_:
_Interface_: `subroutine omp_set_dynamic(set)'
`integer, intent(in) :: set'
_See also_:
*Note OMP_NESTED::, *Note omp_get_nested::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.9.
File: libgomp.info, Node: omp_set_num_threads, Next: omp_init_lock, Prev: omp_set_nested, Up: Runtime Library Routines
2.10 `omp_set_num_threads' - Set upper team size limit
======================================================
_Description_:
Specifies the number of threads used by default in subsequent
parallel sections, if those do not specify a `num_threads' clause.
The argument of `omp_set_num_threads' shall be a positive integer.
_C/C++_:
_Prototype_: `void omp_set_num_threads(int);'
_Fortran_:
_Interface_: `subroutine omp_set_num_threads(set)'
`integer, intent(in) :: set'
_See also_:
*Note OMP_NUM_THREADS::, *Note omp_get_num_threads::, *Note
omp_get_max_threads::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.2.1.
File: libgomp.info, Node: omp_init_lock, Next: omp_set_lock, Prev: omp_set_num_threads, Up: Runtime Library Routines
2.11 `omp_init_lock' - Initialize simple lock
=============================================
_Description_:
Initialize a simple lock. After initialization, the lock is in an
unlocked state.
_C/C++_:
_Prototype_: `void omp_init_lock(omp_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_init_lock(lock)'
`integer(omp_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_destroy_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.1.
File: libgomp.info, Node: omp_set_lock, Next: omp_test_lock, Prev: omp_init_lock, Up: Runtime Library Routines
2.12 `omp_set_lock' - Wait for and set simple lock
==================================================
_Description_:
Before setting a simple lock, the lock variable must be
initialized by `omp_init_lock'. The calling thread is blocked
until the lock is available. If the lock is already held by the
current thread, a deadlock occurs.
_C/C++_:
_Prototype_: `void omp_set_lock(omp_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_set_lock(lock)'
`integer(omp_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_init_lock::, *Note omp_test_lock::, *Note
omp_unset_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.3.
File: libgomp.info, Node: omp_test_lock, Next: omp_unset_lock, Prev: omp_set_lock, Up: Runtime Library Routines
2.13 `omp_test_lock' - Test and set simple lock if available
============================================================
_Description_:
Before setting a simple lock, the lock variable must be
initialized by `omp_init_lock'. Contrary to `omp_set_lock',
`omp_test_lock' does not block if the lock is not available. This
function returns `true' upon success,`false' otherwise. Here,
`true' and `false' represent their language-specific counterparts.
_C/C++_:
_Prototype_: `int omp_test_lock(omp_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_test_lock(lock)'
`logical(omp_logical_kind) :: omp_test_lock'
`integer(omp_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_init_lock::, *Note omp_set_lock::, *Note omp_set_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.5.
File: libgomp.info, Node: omp_unset_lock, Next: omp_destroy_lock, Prev: omp_test_lock, Up: Runtime Library Routines
2.14 `omp_unset_lock' - Unset simple lock
=========================================
_Description_:
A simple lock about to be unset must have been locked by
`omp_set_lock' or `omp_test_lock' before. In addition, the lock
must be held by the thread calling `omp_unset_lock'. Then, the
lock becomes unlocked. If one ore more threads attempted to set
the lock before, one of them is chosen to, again, set the lock for
itself.
_C/C++_:
_Prototype_: `void omp_unset_lock(omp_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_unset_lock(lock)'
`integer(omp_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_set_lock::, *Note omp_test_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.4.
File: libgomp.info, Node: omp_destroy_lock, Next: omp_init_nest_lock, Prev: omp_unset_lock, Up: Runtime Library Routines
2.15 `omp_destroy_lock' - Destroy simple lock
=============================================
_Description_:
Destroy a simple lock. In order to be destroyed, a simple lock
must be in the unlocked state.
_C/C++_:
_Prototype_: `void omp_destroy_lock(omp_lock_t *);'
_Fortran_:
_Interface_: `subroutine omp_destroy_lock(lock)'
`integer(omp_lock_kind), intent(inout) :: lock'
_See also_:
*Note omp_init_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.2.
File: libgomp.info, Node: omp_init_nest_lock, Next: omp_set_nest_lock, Prev: omp_destroy_lock, Up: Runtime Library Routines
2.16 `omp_init_nest_lock' - Initialize nested lock
==================================================
_Description_:
Initialize a nested lock. After initialization, the lock is in an
unlocked state and the nesting count is set to zero.
_C/C++_:
_Prototype_: `void omp_init_nest_lock(omp_nest_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_init_nest_lock(lock)'
`integer(omp_nest_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_destroy_nest_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.1.
File: libgomp.info, Node: omp_set_nest_lock, Next: omp_test_nest_lock, Prev: omp_init_nest_lock, Up: Runtime Library Routines
2.17 `omp_set_nest_lock' - Wait for and set simple lock
=======================================================
_Description_:
Before setting a nested lock, the lock variable must be
initialized by `omp_init_nest_lock'. The calling thread is blocked
until the lock is available. If the lock is already held by the
current thread, the nesting count for the lock in incremented.
_C/C++_:
_Prototype_: `void omp_set_nest_lock(omp_nest_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_set_nest_lock(lock)'
`integer(omp_nest_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_init_nest_lock::, *Note omp_unset_nest_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.3.
File: libgomp.info, Node: omp_test_nest_lock, Next: omp_unset_nest_lock, Prev: omp_set_nest_lock, Up: Runtime Library Routines
2.18 `omp_test_nest_lock' - Test and set nested lock if available
=================================================================
_Description_:
Before setting a nested lock, the lock variable must be
initialized by `omp_init_nest_lock'. Contrary to
`omp_set_nest_lock', `omp_test_nest_lock' does not block if the
lock is not available. If the lock is already held by the current
thread, the new nesting count is returned. Otherwise, the return
value equals zero.
_C/C++_:
_Prototype_: `int omp_test_nest_lock(omp_nest_lock_t *lock);'
_Fortran_:
_Interface_: `integer function omp_test_nest_lock(lock)'
`integer(omp_integer_kind) :: omp_test_nest_lock'
`integer(omp_nest_lock_kind), intent(inout) :: lock'
_See also_:
*Note omp_init_lock::, *Note omp_set_lock::, *Note omp_set_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.5.
File: libgomp.info, Node: omp_unset_nest_lock, Next: omp_destroy_nest_lock, Prev: omp_test_nest_lock, Up: Runtime Library Routines
2.19 `omp_unset_nest_lock' - Unset nested lock
==============================================
_Description_:
A nested lock about to be unset must have been locked by
`omp_set_nested_lock' or `omp_test_nested_lock' before. In
addition, the lock must be held by the thread calling
`omp_unset_nested_lock'. If the nesting count drops to zero, the
lock becomes unlocked. If one ore more threads attempted to set
the lock before, one of them is chosen to, again, set the lock for
itself.
_C/C++_:
_Prototype_: `void omp_unset_nest_lock(omp_nest_lock_t *lock);'
_Fortran_:
_Interface_: `subroutine omp_unset_nest_lock(lock)'
`integer(omp_nest_lock_kind), intent(out) :: lock'
_See also_:
*Note omp_set_nest_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.4.
File: libgomp.info, Node: omp_destroy_nest_lock, Next: omp_get_wtick, Prev: omp_unset_nest_lock, Up: Runtime Library Routines
2.20 `omp_destroy_nest_lock' - Destroy nested lock
==================================================
_Description_:
Destroy a nested lock. In order to be destroyed, a nested lock
must be in the unlocked state and its nesting count must equal
zero.
_C/C++_:
_Prototype_: `void omp_destroy_nest_lock(omp_nest_lock_t *);'
_Fortran_:
_Interface_: `subroutine omp_destroy_nest_lock(lock)'
`integer(omp_nest_lock_kind), intent(inout) :: lock'
_See also_:
*Note omp_init_lock::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.3.2.
File: libgomp.info, Node: omp_get_wtick, Next: omp_get_wtime, Prev: omp_destroy_nest_lock, Up: Runtime Library Routines
2.21 `omp_get_wtick' - Get timer precision
==========================================
_Description_:
Gets the timer precision, i.e., the number of seconds between two
successive clock ticks.
_C/C++_:
_Prototype_: `double omp_get_wtick();'
_Fortran_:
_Interface_: `double precision function omp_get_wtick()'
_See also_:
*Note omp_get_wtime::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.4.2.
File: libgomp.info, Node: omp_get_wtime, Prev: omp_get_wtick, Up: Runtime Library Routines
2.22 `omp_get_wtime' - Elapsed wall clock time
==============================================
_Description_:
Elapsed wall clock time in seconds. The time is measured per
thread, no guarantee can bee made that two distinct threads
measure the same time. Time is measured from some "time in the
past". On POSIX compliant systems the seconds since the Epoch
(00:00:00 UTC, January 1, 1970) are returned.
_C/C++_:
_Prototype_: `double omp_get_wtime();'
_Fortran_:
_Interface_: `double precision function omp_get_wtime()'
_See also_:
*Note omp_get_wtick::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 3.4.1.
File: libgomp.info, Node: Environment Variables, Next: The libgomp ABI, Prev: Runtime Library Routines, Up: Top
3 Environment Variables
***********************
The variables `OMP_DYNAMIC', `OMP_NESTED', `OMP_NUM_THREADS' and
`OMP_SCHEDULE' are defined by section 4 of the OpenMP specifications in
version 2.5, while `GOMP_CPU_AFFINITY' and `GOMP_STACKSIZE' are GNU
extensions.
* Menu:
* OMP_DYNAMIC:: Dynamic adjustment of threads
* OMP_NESTED:: Nested parallel regions
* OMP_NUM_THREADS:: Specifies the number of threads to use
* OMP_SCHEDULE:: How threads are scheduled
* GOMP_CPU_AFFINITY:: Bind threads to specific CPUs
* GOMP_STACKSIZE:: Set default thread stack size
File: libgomp.info, Node: OMP_DYNAMIC, Next: OMP_NESTED, Up: Environment Variables
3.1 `OMP_DYNAMIC' - Dynamic adjustment of threads
=================================================
_Description_:
Enable or disable the dynamic adjustment of the number of threads
within a team. The value of this environment variable shall be
`TRUE' or `FALSE'. If undefined, dynamic adjustment is disabled by
default.
_See also_:
*Note omp_set_dynamic::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 4.3
File: libgomp.info, Node: OMP_NESTED, Next: OMP_NUM_THREADS, Prev: OMP_DYNAMIC, Up: Environment Variables
3.2 `OMP_NESTED' - Nested parallel regions
==========================================
_Description_:
Enable or disable nested parallel regions, i.e., whether team
members are allowed to create new teams. The value of this
environment variable shall be `TRUE' or `FALSE'. If undefined,
nested parallel regions are disabled by default.
_See also_:
*Note omp_set_nested::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 4.4
File: libgomp.info, Node: OMP_NUM_THREADS, Next: OMP_SCHEDULE, Prev: OMP_NESTED, Up: Environment Variables
3.3 `OMP_NUM_THREADS' - Specifies the number of threads to use
==============================================================
_Description_:
Specifies the default number of threads to use in parallel
regions. The value of this variable shall be positive integer. If
undefined one thread per CPU online is used.
_See also_:
*Note omp_set_num_threads::
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), section 4.2
File: libgomp.info, Node: OMP_SCHEDULE, Next: GOMP_CPU_AFFINITY, Prev: OMP_NUM_THREADS, Up: Environment Variables
3.4 `OMP_SCHEDULE' - How threads are scheduled
==============================================
_Description_:
Allows to specify `schedule type' and `chunk size'. The value of
the variable shall have the form: `type[,chunk]' where `type' is
one of `static', `dynamic' or `guided'. The optional `chunk size'
shall be a positive integer. If undefined, dynamic scheduling and
a chunk size of 1 is used.
_Reference_:
OpenMP specifications v2.5 (http://www.openmp.org/), sections
2.5.1 and 4.1
File: libgomp.info, Node: GOMP_CPU_AFFINITY, Next: GOMP_STACKSIZE, Prev: OMP_SCHEDULE, Up: Environment Variables
3.5 `GOMP_CPU_AFFINITY' - Bind threads to specific CPUs
=======================================================
_Description_:
A patch for this extension has been submitted, but was not yet
applied at the time of writing.
_Reference_:
GCC Patches Mailinglist
(http://gcc.gnu.org/ml/gcc-patches/2006-05/msg00982.html) GCC
Patches Mailinglist
(http://gcc.gnu.org/ml/gcc-patches/2006-05/msg01133.html)
File: libgomp.info, Node: GOMP_STACKSIZE, Prev: GOMP_CPU_AFFINITY, Up: Environment Variables
3.6 `GOMP_STACKSIZE' - Set default thread stack size
====================================================
_Description_:
Set the default thread stack size in kilobytes. This is in
opposition to `pthread_attr_setstacksize' which gets the number of
bytes as an argument. If the stacksize can not be set due to
system constraints, an error is reported and the initial stacksize
is left unchanged. If undefined, the stack size is system
dependent.
_Reference_:
GCC Patches Mailinglist
(http://gcc.gnu.org/ml/gcc-patches/2006-06/msg00493.html), GCC
Patches Mailinglist
(http://gcc.gnu.org/ml/gcc-patches/2006-06/msg00496.html)
File: libgomp.info, Node: The libgomp ABI, Next: Reporting Bugs, Prev: Environment Variables, Up: Top
4 The libgomp ABI
*****************
The following sections present notes on the external ABI as presented
by libgomp. Only maintainers should need them.
* Menu:
* Implementing MASTER construct::
* Implementing CRITICAL construct::
* Implementing ATOMIC construct::
* Implementing FLUSH construct::
* Implementing BARRIER construct::
* Implementing THREADPRIVATE construct::
* Implementing PRIVATE clause::
* Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses::
* Implementing REDUCTION clause::
* Implementing PARALLEL construct::
* Implementing FOR construct::
* Implementing ORDERED construct::
* Implementing SECTIONS construct::
* Implementing SINGLE construct::
File: libgomp.info, Node: Implementing MASTER construct, Next: Implementing CRITICAL construct, Up: The libgomp ABI
4.1 Implementing MASTER construct
=================================
if (omp_get_thread_num () == 0)
block
Alternately, we generate two copies of the parallel subfunction and
only include this in the version run by the master thread. Surely
that's not worthwhile though...
File: libgomp.info, Node: Implementing CRITICAL construct, Next: Implementing ATOMIC construct, Prev: Implementing MASTER construct, Up: The libgomp ABI
4.2 Implementing CRITICAL construct
===================================
Without a specified name,
void GOMP_critical_start (void);
void GOMP_critical_end (void);
so that we don't get COPY relocations from libgomp to the main
application.
With a specified name, use omp_set_lock and omp_unset_lock with name
being transformed into a variable declared like
omp_lock_t gomp_critical_user_<name> __attribute__((common))
Ideally the ABI would specify that all zero is a valid unlocked
state, and so we wouldn't actually need to initialize this at startup.
File: libgomp.info, Node: Implementing ATOMIC construct, Next: Implementing FLUSH construct, Prev: Implementing CRITICAL construct, Up: The libgomp ABI
4.3 Implementing ATOMIC construct
=================================
The target should implement the `__sync' builtins.
Failing that we could add
void GOMP_atomic_enter (void)
void GOMP_atomic_exit (void)
which reuses the regular lock code, but with yet another lock object
private to the library.
File: libgomp.info, Node: Implementing FLUSH construct, Next: Implementing BARRIER construct, Prev: Implementing ATOMIC construct, Up: The libgomp ABI
4.4 Implementing FLUSH construct
================================
Expands to the `__sync_synchronize' builtin.
File: libgomp.info, Node: Implementing BARRIER construct, Next: Implementing THREADPRIVATE construct, Prev: Implementing FLUSH construct, Up: The libgomp ABI
4.5 Implementing BARRIER construct
==================================
void GOMP_barrier (void)
File: libgomp.info, Node: Implementing THREADPRIVATE construct, Next: Implementing PRIVATE clause, Prev: Implementing BARRIER construct, Up: The libgomp ABI
4.6 Implementing THREADPRIVATE construct
========================================
In _most_ cases we can map this directly to `__thread'. Except that
OMP allows constructors for C++ objects. We can either refuse to
support this (how often is it used?) or we can implement something akin
to .ctors.
Even more ideally, this ctor feature is handled by extensions to the
main pthreads library. Failing that, we can have a set of entry points
to register ctor functions to be called.
File: libgomp.info, Node: Implementing PRIVATE clause, Next: Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses, Prev: Implementing THREADPRIVATE construct, Up: The libgomp ABI
4.7 Implementing PRIVATE clause
===============================
In association with a PARALLEL, or within the lexical extent of a
PARALLEL block, the variable becomes a local variable in the parallel
subfunction.
In association with FOR or SECTIONS blocks, create a new automatic
variable within the current function. This preserves the semantic of
new variable creation.
File: libgomp.info, Node: Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses, Next: Implementing REDUCTION clause, Prev: Implementing PRIVATE clause, Up: The libgomp ABI
4.8 Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses
========================================================================
Seems simple enough for PARALLEL blocks. Create a private struct for
communicating between parent and subfunction. In the parent, copy in
values for scalar and "small" structs; copy in addresses for others
TREE_ADDRESSABLE types. In the subfunction, copy the value into the
local variable.
Not clear at all what to do with bare FOR or SECTION blocks. The
only thing I can figure is that we do something like
#pragma omp for firstprivate(x) lastprivate(y)
for (int i = 0; i < n; ++i)
body;
which becomes
{
int x = x, y;
// for stuff
if (i == n)
y = y;
}
where the "x=x" and "y=y" assignments actually have different uids
for the two variables, i.e. not something you could write directly in
C. Presumably this only makes sense if the "outer" x and y are global
variables.
COPYPRIVATE would work the same way, except the structure broadcast
would have to happen via SINGLE machinery instead.
File: libgomp.info, Node: Implementing REDUCTION clause, Next: Implementing PARALLEL construct, Prev: Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses, Up: The libgomp ABI
4.9 Implementing REDUCTION clause
=================================
The private struct mentioned in the previous section should have a
pointer to an array of the type of the variable, indexed by the
thread's TEAM_ID. The thread stores its final value into the array,
and after the barrier the master thread iterates over the array to
collect the values.
File: libgomp.info, Node: Implementing PARALLEL construct, Next: Implementing FOR construct, Prev: Implementing REDUCTION clause, Up: The libgomp ABI
4.10 Implementing PARALLEL construct
====================================
#pragma omp parallel
{
body;
}
becomes
void subfunction (void *data)
{
use data;
body;
}
setup data;
GOMP_parallel_start (subfunction, &data, num_threads);
subfunction (&data);
GOMP_parallel_end ();
void GOMP_parallel_start (void (*fn)(void *), void *data, unsigned num_threads)
The FN argument is the subfunction to be run in parallel.
The DATA argument is a pointer to a structure used to communicate
data in and out of the subfunction, as discussed above with respect to
FIRSTPRIVATE et al.
The NUM_THREADS argument is 1 if an IF clause is present and false,
or the value of the NUM_THREADS clause, if present, or 0.
The function needs to create the appropriate number of threads
and/or launch them from the dock. It needs to create the team
structure and assign team ids.
void GOMP_parallel_end (void)
Tears down the team and returns us to the previous
`omp_in_parallel()' state.
File: libgomp.info, Node: Implementing FOR construct, Next: Implementing ORDERED construct, Prev: Implementing PARALLEL construct, Up: The libgomp ABI
4.11 Implementing FOR construct
===============================
#pragma omp parallel for
for (i = lb; i <= ub; i++)
body;
becomes
void subfunction (void *data)
{
long _s0, _e0;
while (GOMP_loop_static_next (&_s0, &_e0))
{
long _e1 = _e0, i;
for (i = _s0; i < _e1; i++)
body;
}
GOMP_loop_end_nowait ();
}
GOMP_parallel_loop_static (subfunction, NULL, 0, lb, ub+1, 1, 0);
subfunction (NULL);
GOMP_parallel_end ();
#pragma omp for schedule(runtime)
for (i = 0; i < n; i++)
body;
becomes
{
long i, _s0, _e0;
if (GOMP_loop_runtime_start (0, n, 1, &_s0, &_e0))
do {
long _e1 = _e0;
for (i = _s0, i < _e0; i++)
body;
} while (GOMP_loop_runtime_next (&_s0, _&e0));
GOMP_loop_end ();
}
Note that while it looks like there is trickyness to propagating a
non-constant STEP, there isn't really. We're explicitly allowed to
evaluate it as many times as we want, and any variables involved should
automatically be handled as PRIVATE or SHARED like any other variables.
So the expression should remain evaluable in the subfunction. We can
also pull it into a local variable if we like, but since its supposed
to remain unchanged, we can also not if we like.
If we have SCHEDULE(STATIC), and no ORDERED, then we ought to be
able to get away with no work-sharing context at all, since we can
simply perform the arithmetic directly in each thread to divide up the
iterations. Which would mean that we wouldn't need to call any of
these routines.
There are separate routines for handling loops with an ORDERED
clause. Bookkeeping for that is non-trivial...
File: libgomp.info, Node: Implementing ORDERED construct, Next: Implementing SECTIONS construct, Prev: Implementing FOR construct, Up: The libgomp ABI
4.12 Implementing ORDERED construct
===================================
void GOMP_ordered_start (void)
void GOMP_ordered_end (void)
File: libgomp.info, Node: Implementing SECTIONS construct, Next: Implementing SINGLE construct, Prev: Implementing ORDERED construct, Up: The libgomp ABI
4.13 Implementing SECTIONS construct
====================================
A block as
#pragma omp sections
{
#pragma omp section
stmt1;
#pragma omp section
stmt2;
#pragma omp section
stmt3;
}
becomes
for (i = GOMP_sections_start (3); i != 0; i = GOMP_sections_next ())
switch (i)
{
case 1:
stmt1;
break;
case 2:
stmt2;
break;
case 3:
stmt3;
break;
}
GOMP_barrier ();
File: libgomp.info, Node: Implementing SINGLE construct, Prev: Implementing SECTIONS construct, Up: The libgomp ABI
4.14 Implementing SINGLE construct
==================================
A block like
#pragma omp single
{
body;
}
becomes
if (GOMP_single_start ())
body;
GOMP_barrier ();
while
#pragma omp single copyprivate(x)
body;
becomes
datap = GOMP_single_copy_start ();
if (datap == NULL)
{
body;
data.x = x;
GOMP_single_copy_end (&data);
}
else
x = datap->x;
GOMP_barrier ();
File: libgomp.info, Node: Reporting Bugs, Next: Copying, Prev: The libgomp ABI, Up: Top
5 Reporting Bugs
****************
Bugs in the GNU OpenMP implementation should be reported via bugzilla
(http://gcc.gnu.org/bugzilla/). In all cases, please add "openmp" to
the keywords field in the bug report.
File: libgomp.info, Node: Copying, Next: GNU Free Documentation License, Prev: Reporting Bugs, Up: Top
GNU GENERAL PUBLIC LICENSE
**************************
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
Preamble
========
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Appendix: How to Apply These Terms to Your New Programs
=======================================================
If you develop a new program, and you want it to be of the greatest
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ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
Copyright (C) YEAR NAME OF AUTHOR
This program is free software; you can redistribute it and/or modify
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(at your option) any later version.
This program is distributed in the hope that it will be useful,
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GNU General Public License for more details.
You should have received a copy of the GNU General Public License
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Also add information on how to contact you by electronic and paper
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`Gnomovision' (which makes passes at compilers) written by James Hacker.
SIGNATURE OF TY COON, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your
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File: libgomp.info, Node: GNU Free Documentation License, Next: Funding, Prev: Copying, Up: Top
GNU Free Documentation License
******************************
Version 1.2, November 2002
Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
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being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium,
that contains a notice placed by the copyright holder saying it
can be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You
accept the license if you copy, modify or distribute the work in a
way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could
fall directly within that overall subject. (Thus, if the Document
is in part a textbook of mathematics, a Secondary Section may not
explain any mathematics.) The relationship could be a matter of
historical connection with the subject or with related matters, or
of legal, commercial, philosophical, ethical or political position
regarding them.
The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in
the notice that says that the Document is released under this
License. If a section does not fit the above definition of
Secondary then it is not allowed to be designated as Invariant.
The Document may contain zero Invariant Sections. If the Document
does not identify any Invariant Sections then there are none.
The "Cover Texts" are certain short passages of text that are
listed, as Front-Cover Texts or Back-Cover Texts, in the notice
that says that the Document is released under this License. A
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images
composed of pixels) generic paint programs or (for drawings) some
widely available drawing editor, and that is suitable for input to
text formatters or for automatic translation to a variety of
formats suitable for input to text formatters. A copy made in an
otherwise Transparent file format whose markup, or absence of
markup, has been arranged to thwart or discourage subsequent
modification by readers is not Transparent. An image format is
not Transparent if used for any substantial amount of text. A
copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format,
SGML or XML using a publicly available DTD, and
standard-conforming simple HTML, PostScript or PDF designed for
human modification. Examples of transparent image formats include
PNG, XCF and JPG. Opaque formats include proprietary formats that
can be read and edited only by proprietary word processors, SGML or
XML for which the DTD and/or processing tools are not generally
available, and the machine-generated HTML, PostScript or PDF
produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the
work's title, preceding the beginning of the body of the text.
A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
Warranty Disclaimers are considered to be included by reference in
this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License
applies to the Document are reproduced in all copies, and that you
add no other conditions whatsoever to those of this License. You
may not use technical measures to obstruct or control the reading
or further copying of the copies you make or distribute. However,
you may accept compensation in exchange for copies. If you
distribute a large enough number of copies you must also follow
the conditions in section 3.
You may also lend copies, under the same conditions stated above,
and you may publicly display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
the Document's license notice requires Cover Texts, you must
enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and
Back-Cover Texts on the back cover. Both covers must also clearly
and legibly identify you as the publisher of these copies. The
front cover must present the full title with all words of the
title equally prominent and visible. You may add other material
on the covers in addition. Copying with changes limited to the
covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in
other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto
adjacent pages.
If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a
machine-readable Transparent copy along with each Opaque copy, or
state in or with each Opaque copy a computer-network location from
which the general network-using public has access to download
using public-standard network protocols a complete Transparent
copy of the Document, free of added material. If you use the
latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or
retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of
copies, to give them a chance to provide you with an updated
version of the Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with
the Modified Version filling the role of the Document, thus
licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these
things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of
previous versions (which should, if there were any, be listed
in the History section of the Document). You may use the
same title as a previous version if the original publisher of
that version gives permission.
B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the
principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you
from this requirement.
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in
the Addendum below.
G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on
the Title Page. If there is no section Entitled "History" in
the Document, create one stating the title, year, authors,
and publisher of the Document as given on its Title Page,
then add an item describing the Modified Version as stated in
the previous sentence.
J. Preserve the network location, if any, given in the Document
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in
the "History" section. You may omit a network location for a
work that was published at least four years before the
Document itself, or if the original publisher of the version
it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the
section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section
titles.
M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
Section.
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
other section titles.
You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text
has been approved by an organization as the authoritative
definition of a standard.
You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end
of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity
you are acting on behalf of, you may not add another; but you may
replace the old one, on explicit permission from the previous
publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination
all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You
must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the
documents in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of
that document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of
a storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided for under this License. Any other
attempt to copy, modify, sublicense or distribute the Document is
void, and will automatically terminate your rights under this
License. However, parties who have received copies, or rights,
from you under this License will not have their licenses
terminated so long as such parties remain in full compliance.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
`http://www.gnu.org/copyleft/'.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If
the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation.
ADDENDUM: How to use this License for your documents
====================================================
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.
File: libgomp.info, Node: Funding, Next: Index, Prev: GNU Free Documentation License, Up: Top
Funding Free Software
*********************
If you want to have more free software a few years from now, it makes
sense for you to help encourage people to contribute funds for its
development. The most effective approach known is to encourage
commercial redistributors to donate.
Users of free software systems can boost the pace of development by
encouraging for-a-fee distributors to donate part of their selling price
to free software developers--the Free Software Foundation, and others.
The way to convince distributors to do this is to demand it and
expect it from them. So when you compare distributors, judge them
partly by how much they give to free software development. Show
distributors they must compete to be the one who gives the most.
To make this approach work, you must insist on numbers that you can
compare, such as, "We will donate ten dollars to the Frobnitz project
for each disk sold." Don't be satisfied with a vague promise, such as
"A portion of the profits are donated," since it doesn't give a basis
for comparison.
Even a precise fraction "of the profits from this disk" is not very
meaningful, since creative accounting and unrelated business decisions
can greatly alter what fraction of the sales price counts as profit.
If the price you pay is $50, ten percent of the profit is probably less
than a dollar; it might be a few cents, or nothing at all.
Some redistributors do development work themselves. This is useful
too; but to keep everyone honest, you need to inquire how much they do,
and what kind. Some kinds of development make much more long-term
difference than others. For example, maintaining a separate version of
a program contributes very little; maintaining the standard version of a
program for the whole community contributes much. Easy new ports
contribute little, since someone else would surely do them; difficult
ports such as adding a new CPU to the GNU Compiler Collection
contribute more; major new features or packages contribute the most.
By establishing the idea that supporting further development is "the
proper thing to do" when distributing free software for a fee, we can
assure a steady flow of resources into making more free software.
Copyright (C) 1994 Free Software Foundation, Inc.
Verbatim copying and redistribution of this section is permitted
without royalty; alteration is not permitted.
File: libgomp.info, Node: Index, Prev: Funding, Up: Top
Index
*****