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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.
* Library 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 3.1.
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 3.1. The routines are structured in
following three parts:
Control threads, processors and the parallel environment.
* Menu:
* omp_get_active_level:: Number of active parallel regions
* omp_get_ancestor_thread_num:: Ancestor thread ID
* omp_get_dynamic:: Dynamic teams setting
* omp_get_level:: Number of parallel regions
* omp_get_max_active_levels:: Maximum number of active regions
* omp_get_max_threads:: Maximum number of threads of parallel region
* 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_schedule:: Obtain the runtime scheduling method
* omp_get_team_size:: Number of threads in a team
* omp_get_thread_limit:: Maximum number of threads
* omp_get_thread_num:: Current thread ID
* omp_in_parallel:: Whether a parallel region is active
* omp_in_final:: Whether in final or included task region
* omp_set_dynamic:: Enable/disable dynamic teams
* omp_set_max_active_levels:: Limits the number of active parallel regions
* omp_set_nested:: Enable/disable nested parallel regions
* omp_set_num_threads:: Set upper team size limit
* omp_set_schedule:: Set the runtime scheduling method
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_active_level, Next: omp_get_ancestor_thread_num, Up: Runtime Library Routines
2.1 'omp_get_active_level' - Number of parallel regions
=======================================================
_Description_:
This function returns the nesting level for the active parallel
blocks, which enclose the calling call.
_C/C++_
_Prototype_: 'int omp_get_active_level(void);'
_Fortran_:
_Interface_: 'integer function omp_get_active_level()'
_See also_:
*note omp_get_level::, *note omp_get_max_active_levels::, *note
omp_set_max_active_levels::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.19.
File: libgomp.info, Node: omp_get_ancestor_thread_num, Next: omp_get_dynamic, Prev: omp_get_active_level, Up: Runtime Library Routines
2.2 'omp_get_ancestor_thread_num' - Ancestor thread ID
======================================================
_Description_:
This function returns the thread identification number for the
given nesting level of the current thread. For values of LEVEL
outside zero to 'omp_get_level' -1 is returned; if LEVEL is
'omp_get_level' the result is identical to 'omp_get_thread_num'.
_C/C++_
_Prototype_: 'int omp_get_ancestor_thread_num(int level);'
_Fortran_:
_Interface_: 'integer function omp_get_ancestor_thread_num(level)'
'integer level'
_See also_:
*note omp_get_level::, *note omp_get_thread_num::, *note
omp_get_team_size::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.17.
File: libgomp.info, Node: omp_get_dynamic, Next: omp_get_level, Prev: omp_get_ancestor_thread_num, Up: Runtime Library Routines
2.3 '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(void);'
_Fortran_:
_Interface_: 'logical function omp_get_dynamic()'
_See also_:
*note omp_set_dynamic::, *note OMP_DYNAMIC::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.8.
File: libgomp.info, Node: omp_get_level, Next: omp_get_max_active_levels, Prev: omp_get_dynamic, Up: Runtime Library Routines
2.4 'omp_get_level' - Obtain the current nesting level
======================================================
_Description_:
This function returns the nesting level for the parallel blocks,
which enclose the calling call.
_C/C++_
_Prototype_: 'int omp_get_level(void);'
_Fortran_:
_Interface_: 'integer function omp_level()'
_See also_:
*note omp_get_active_level::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.16.
File: libgomp.info, Node: omp_get_max_active_levels, Next: omp_get_max_threads, Prev: omp_get_level, Up: Runtime Library Routines
2.5 'omp_get_max_active_levels' - Maximum number of active regions
==================================================================
_Description_:
This function obtains the maximum allowed number of nested, active
parallel regions.
_C/C++_
_Prototype_: 'int omp_get_max_active_levels(void);'
_Fortran_:
_Interface_: 'integer function omp_get_max_active_levels()'
_See also_:
*note omp_set_max_active_levels::, *note omp_get_active_level::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.15.
File: libgomp.info, Node: omp_get_max_threads, Next: omp_get_nested, Prev: omp_get_max_active_levels, Up: Runtime Library Routines
2.6 'omp_get_max_threads' - Maximum number of threads of parallel region
========================================================================
_Description_:
Return the maximum number of threads used for the current parallel
region that does not use the clause 'num_threads'.
_C/C++_:
_Prototype_: 'int omp_get_max_threads(void);'
_Fortran_:
_Interface_: 'integer function omp_get_max_threads()'
_See also_:
*note omp_set_num_threads::, *note omp_set_dynamic::, *note
omp_get_thread_limit::
_Reference_:
OpenMP specifications v3.1 (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
2.7 '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(void);'
_Fortran_:
_Interface_: 'logical function omp_get_nested()'
_See also_:
*note omp_set_nested::, *note OMP_NESTED::
_Reference_:
OpenMP specifications v3.1 (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
2.8 'omp_get_num_procs' - Number of processors online
=====================================================
_Description_:
Returns the number of processors online.
_C/C++_:
_Prototype_: 'int omp_get_num_procs(void);'
_Fortran_:
_Interface_: 'integer function omp_get_num_procs()'
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.5.
File: libgomp.info, Node: omp_get_num_threads, Next: omp_get_schedule, Prev: omp_get_num_procs, Up: Runtime Library Routines
2.9 'omp_get_num_threads' - Size of the active team
===================================================
_Description_:
Returns 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(void);'
_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 v3.1 (http://www.openmp.org/), section 3.2.2.
File: libgomp.info, Node: omp_get_schedule, Next: omp_get_team_size, Prev: omp_get_num_threads, Up: Runtime Library Routines
2.10 'omp_get_schedule' - Obtain the runtime scheduling method
==============================================================
_Description_:
Obtain the runtime scheduling method. The KIND argument will be
set to the value 'omp_sched_static', 'omp_sched_dynamic',
'omp_sched_guided' or 'omp_sched_auto'. The second argument,
MODIFIER, is set to the chunk size.
_C/C++_
_Prototype_: 'void omp_schedule(omp_sched_t *kind, int *modifier);'
_Fortran_:
_Interface_: 'subroutine omp_schedule(kind, modifier)'
'integer(kind=omp_sched_kind) kind'
'integer modifier'
_See also_:
*note omp_set_schedule::, *note OMP_SCHEDULE::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.12.
File: libgomp.info, Node: omp_get_team_size, Next: omp_get_thread_limit, Prev: omp_get_schedule, Up: Runtime Library Routines
2.11 'omp_get_team_size' - Number of threads in a team
======================================================
_Description_:
This function returns the number of threads in a thread team to
which either the current thread or its ancestor belongs. For
values of LEVEL outside zero to 'omp_get_level', -1 is returned; if
LEVEL is zero, 1 is returned, and for 'omp_get_level', the result
is identical to 'omp_get_num_threads'.
_C/C++_:
_Prototype_: 'int omp_get_team_size(int level);'
_Fortran_:
_Interface_: 'integer function omp_get_team_size(level)'
'integer level'
_See also_:
*note omp_get_num_threads::, *note omp_get_level::, *note
omp_get_ancestor_thread_num::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.18.
File: libgomp.info, Node: omp_get_thread_limit, Next: omp_get_thread_num, Prev: omp_get_team_size, Up: Runtime Library Routines
2.12 'omp_get_thread_limit' - Maximum number of threads
=======================================================
_Description_:
Return the maximum number of threads of the program.
_C/C++_:
_Prototype_: 'int omp_get_thread_limit(void);'
_Fortran_:
_Interface_: 'integer function omp_get_thread_limit()'
_See also_:
*note omp_get_max_threads::, *note OMP_THREAD_LIMIT::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.13.
File: libgomp.info, Node: omp_get_thread_num, Next: omp_in_parallel, Prev: omp_get_thread_limit, Up: Runtime Library Routines
2.13 'omp_get_thread_num' - Current thread ID
=============================================
_Description_:
Returns a unique thread identification number within the current
team. 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_num_threads'-1 inclusive. The return value of the
master thread of a team is always 0.
_C/C++_:
_Prototype_: 'int omp_get_thread_num(void);'
_Fortran_:
_Interface_: 'integer function omp_get_thread_num()'
_See also_:
*note omp_get_num_threads::, *note omp_get_ancestor_thread_num::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.4.
File: libgomp.info, Node: omp_in_parallel, Next: omp_in_final, Prev: omp_get_thread_num, Up: Runtime Library Routines
2.14 '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(void);'
_Fortran_:
_Interface_: 'logical function omp_in_parallel()'
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.6.
File: libgomp.info, Node: omp_in_final, Next: omp_set_dynamic, Prev: omp_in_parallel, Up: Runtime Library Routines
2.15 'omp_in_final' - Whether in final or included task region
==============================================================
_Description_:
This function returns 'true' if currently running in a final or
included task region, 'false' otherwise. Here, 'true' and 'false'
represent their language-specific counterparts.
_C/C++_:
_Prototype_: 'int omp_in_final(void);'
_Fortran_:
_Interface_: 'logical function omp_in_final()'
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.20.
File: libgomp.info, Node: omp_set_dynamic, Next: omp_set_max_active_levels, Prev: omp_in_final, Up: Runtime Library Routines
2.16 '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 set);'
_Fortran_:
_Interface_: 'subroutine omp_set_dynamic(set)'
'logical, intent(in) :: set'
_See also_:
*note OMP_DYNAMIC::, *note omp_get_dynamic::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.7.
File: libgomp.info, Node: omp_set_max_active_levels, Next: omp_set_nested, Prev: omp_set_dynamic, Up: Runtime Library Routines
2.17 'omp_set_max_active_levels' - Limits the number of active parallel regions
===============================================================================
_Description_:
This function limits the maximum allowed number of nested, active
parallel regions.
_C/C++_
_Prototype_: 'void omp_set_max_active_levels(int max_levels);'
_Fortran_:
_Interface_: 'subroutine omp_set_max_active_levels(max_levels)'
'integer max_levels'
_See also_:
*note omp_get_max_active_levels::, *note omp_get_active_level::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.14.
File: libgomp.info, Node: omp_set_nested, Next: omp_set_num_threads, Prev: omp_set_max_active_levels, Up: Runtime Library Routines
2.18 '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_nested(int set);'
_Fortran_:
_Interface_: 'subroutine omp_set_nested(set)'
'logical, intent(in) :: set'
_See also_:
*note OMP_NESTED::, *note omp_get_nested::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.9.
File: libgomp.info, Node: omp_set_num_threads, Next: omp_set_schedule, Prev: omp_set_nested, Up: Runtime Library Routines
2.19 '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 n);'
_Fortran_:
_Interface_: 'subroutine omp_set_num_threads(n)'
'integer, intent(in) :: n'
_See also_:
*note OMP_NUM_THREADS::, *note omp_get_num_threads::, *note
omp_get_max_threads::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.2.1.
File: libgomp.info, Node: omp_set_schedule, Next: omp_init_lock, Prev: omp_set_num_threads, Up: Runtime Library Routines
2.20 'omp_set_schedule' - Set the runtime scheduling method
===========================================================
_Description_:
Sets the runtime scheduling method. The KIND argument can have the
value 'omp_sched_static', 'omp_sched_dynamic', 'omp_sched_guided'
or 'omp_sched_auto'. Except for 'omp_sched_auto', the chunk size
is set to the value of MODIFIER if positive, or to the default
value if zero or negative. For 'omp_sched_auto' the MODIFIER
argument is ignored.
_C/C++_
_Prototype_: 'void omp_set_schedule(omp_sched_t *kind, int
*modifier);'
_Fortran_:
_Interface_: 'subroutine omp_set_schedule(kind, modifier)'
'integer(kind=omp_sched_kind) kind'
'integer modifier'
_See also_:
*note omp_get_schedule:: *note OMP_SCHEDULE::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section
3.2.11.
File: libgomp.info, Node: omp_init_lock, Next: omp_set_lock, Prev: omp_set_schedule, Up: Runtime Library Routines
2.21 '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 v3.1 (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
2.22 '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(inout) :: lock'
_See also_:
*note omp_init_lock::, *note omp_test_lock::, *note
omp_unset_lock::
_Reference_:
OpenMP specifications v3.1 (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
2.23 '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_: 'logical function omp_test_lock(lock)'
'integer(omp_lock_kind), intent(inout) :: lock'
_See also_:
*note omp_init_lock::, *note omp_set_lock::, *note omp_set_lock::
_Reference_:
OpenMP specifications v3.1 (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
2.24 '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 or more threads attempted to set the
lock before, one of them is chosen to, again, set the lock to
itself.
_C/C++_:
_Prototype_: 'void omp_unset_lock(omp_lock_t *lock);'
_Fortran_:
_Interface_: 'subroutine omp_unset_lock(lock)'
'integer(omp_lock_kind), intent(inout) :: lock'
_See also_:
*note omp_set_lock::, *note omp_test_lock::
_Reference_:
OpenMP specifications v3.1 (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
2.25 '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 *lock);'
_Fortran_:
_Interface_: 'subroutine omp_destroy_lock(lock)'
'integer(omp_lock_kind), intent(inout) :: lock'
_See also_:
*note omp_init_lock::
_Reference_:
OpenMP specifications v3.1 (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
2.26 '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 v3.1 (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
2.27 'omp_set_nest_lock' - Wait for and set nested 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 is 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(inout) :: lock'
_See also_:
*note omp_init_nest_lock::, *note omp_unset_nest_lock::
_Reference_:
OpenMP specifications v3.1 (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
2.28 '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_: 'logical function omp_test_nest_lock(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 v3.1 (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
2.29 '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 to
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(inout) :: lock'
_See also_:
*note omp_set_nest_lock::
_Reference_:
OpenMP specifications v3.1 (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
2.30 '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 v3.1 (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
2.31 '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(void);'
_Fortran_:
_Interface_: 'double precision function omp_get_wtick()'
_See also_:
*note omp_get_wtime::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 3.4.2.
File: libgomp.info, Node: omp_get_wtime, Prev: omp_get_wtick, Up: Runtime Library Routines
2.32 'omp_get_wtime' - Elapsed wall clock time
==============================================
_Description_:
Elapsed wall clock time in seconds. The time is measured per
thread, no guarantee can be made that two distinct threads measure
the same time. Time is measured from some "time in the past",
which is an arbitrary time guaranteed not to change during the
execution of the program.
_C/C++_:
_Prototype_: 'double omp_get_wtime(void);'
_Fortran_:
_Interface_: 'double precision function omp_get_wtime()'
_See also_:
*note omp_get_wtick::
_Reference_:
OpenMP specifications v3.1 (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_MAX_ACTIVE_LEVELS', 'OMP_NESTED',
'OMP_NUM_THREADS', 'OMP_SCHEDULE', 'OMP_STACKSIZE','OMP_THREAD_LIMIT'
and 'OMP_WAIT_POLICY' are defined by section 4 of the OpenMP
specifications in version 3.1, while 'GOMP_CPU_AFFINITY' and
'GOMP_STACKSIZE' are GNU extensions.
* Menu:
* OMP_DYNAMIC:: Dynamic adjustment of threads
* OMP_MAX_ACTIVE_LEVELS:: Set the maximum number of nested parallel regions
* OMP_NESTED:: Nested parallel regions
* OMP_NUM_THREADS:: Specifies the number of threads to use
* OMP_STACKSIZE:: Set default thread stack size
* OMP_SCHEDULE:: How threads are scheduled
* OMP_THREAD_LIMIT:: Set the maximum number of threads
* OMP_WAIT_POLICY:: How waiting threads are handled
* OMP_PROC_BIND:: Whether theads may be moved between CPUs
* GOMP_CPU_AFFINITY:: Bind threads to specific CPUs
* GOMP_STACKSIZE:: Set default thread stack size
File: libgomp.info, Node: OMP_DYNAMIC, Next: OMP_MAX_ACTIVE_LEVELS, 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 v3.1 (http://www.openmp.org/), section 4.3
File: libgomp.info, Node: OMP_MAX_ACTIVE_LEVELS, Next: OMP_NESTED, Prev: OMP_DYNAMIC, Up: Environment Variables
3.2 'OMP_MAX_ACTIVE_LEVELS' - Set the maximum number of nested parallel regions
===============================================================================
_Description_:
Specifies the initial value for the maximum number of nested
parallel regions. The value of this variable shall be a positive
integer. If undefined, the number of active levels is unlimited.
_See also_:
*note omp_set_max_active_levels::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 4.8
File: libgomp.info, Node: OMP_NESTED, Next: OMP_NUM_THREADS, Prev: OMP_MAX_ACTIVE_LEVELS, Up: Environment Variables
3.3 '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 v3.1 (http://www.openmp.org/), section 4.5
File: libgomp.info, Node: OMP_NUM_THREADS, Next: OMP_SCHEDULE, Prev: OMP_NESTED, Up: Environment Variables
3.4 '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 a comma-separated list of
positive integers; the value specified the number of threads to use
for the corresponding nested level. If undefined one thread per
CPU is used.
_See also_:
*note omp_set_num_threads::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 4.2
File: libgomp.info, Node: OMP_STACKSIZE, Next: OMP_THREAD_LIMIT, Prev: OMP_SCHEDULE, Up: Environment Variables
3.6 'OMP_STACKSIZE' - Set default thread stack size
===================================================
_Description_:
Set the default thread stack size in kilobytes, unless the number
is suffixed by 'B', 'K', 'M' or 'G', in which case the size is,
respectively, in bytes, kilobytes, megabytes or gigabytes. This is
different from 'pthread_attr_setstacksize' which gets the number of
bytes as an argument. If the stack size cannot be set due to
system constraints, an error is reported and the initial stack size
is left unchanged. If undefined, the stack size is system
dependent.
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), sections 4.6
File: libgomp.info, Node: OMP_SCHEDULE, Next: OMP_STACKSIZE, Prev: OMP_NUM_THREADS, Up: Environment Variables
3.5 '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', 'guided' or 'auto' The optional 'chunk'
size shall be a positive integer. If undefined, dynamic scheduling
and a chunk size of 1 is used.
_See also_:
*note omp_set_schedule::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), sections 2.5.1
and 4.1
File: libgomp.info, Node: OMP_THREAD_LIMIT, Next: OMP_WAIT_POLICY, Prev: OMP_STACKSIZE, Up: Environment Variables
3.7 'OMP_THREAD_LIMIT' - Set the maximum number of threads
==========================================================
_Description_:
Specifies the number of threads to use for the whole program. The
value of this variable shall be a positive integer. If undefined,
the number of threads is not limited.
_See also_:
*note OMP_NUM_THREADS:: *note omp_get_thread_limit::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), section 4.9
File: libgomp.info, Node: OMP_WAIT_POLICY, Next: OMP_PROC_BIND, Prev: OMP_THREAD_LIMIT, Up: Environment Variables
3.8 'OMP_WAIT_POLICY' - How waiting threads are handled
=======================================================
_Description_:
Specifies whether waiting threads should be active or passive. If
the value is 'PASSIVE', waiting threads should not consume CPU
power while waiting; while the value is 'ACTIVE' specifies that
they should.
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), sections 4.7
File: libgomp.info, Node: OMP_PROC_BIND, Next: GOMP_CPU_AFFINITY, Prev: OMP_WAIT_POLICY, Up: Environment Variables
3.9 'OMP_PROC_BIND' - Whether theads may be moved between CPUs
==============================================================
_Description_:
Specifies whether threads may be moved between processors. If set
to 'true', OpenMP theads should not be moved, if set to 'false'
they may be moved.
_See also_:
*note GOMP_CPU_AFFINITY::
_Reference_:
OpenMP specifications v3.1 (http://www.openmp.org/), sections 4.4
File: libgomp.info, Node: GOMP_CPU_AFFINITY, Next: GOMP_STACKSIZE, Prev: OMP_PROC_BIND, Up: Environment Variables
3.10 'GOMP_CPU_AFFINITY' - Bind threads to specific CPUs
========================================================
_Description_:
Binds threads to specific CPUs. The variable should contain a
space-separated or comma-separated list of CPUs. This list may
contain different kinds of entries: either single CPU numbers in
any order, a range of CPUs (M-N) or a range with some stride
(M-N:S). CPU numbers are zero based. For example,
'GOMP_CPU_AFFINITY="0 3 1-2 4-15:2"' will bind the initial thread
to CPU 0, the second to CPU 3, the third to CPU 1, the fourth to
CPU 2, the fifth to CPU 4, the sixth through tenth to CPUs 6, 8,
10, 12, and 14 respectively and then start assigning back from the
beginning of the list. 'GOMP_CPU_AFFINITY=0' binds all threads to
CPU 0.
There is no GNU OpenMP library routine to determine whether a CPU
affinity specification is in effect. As a workaround,
language-specific library functions, e.g., 'getenv' in C or
'GET_ENVIRONMENT_VARIABLE' in Fortran, may be used to query the
setting of the 'GOMP_CPU_AFFINITY' environment variable. A defined
CPU affinity on startup cannot be changed or disabled during the
runtime of the application.
If this environment variable is omitted, the host system will
handle the assignment of threads to CPUs.
_See also_:
*note OMP_PROC_BIND::
File: libgomp.info, Node: GOMP_STACKSIZE, Prev: GOMP_CPU_AFFINITY, Up: Environment Variables
3.11 'GOMP_STACKSIZE' - Set default thread stack size
=====================================================
_Description_:
Set the default thread stack size in kilobytes. This is different
from 'pthread_attr_setstacksize' which gets the number of bytes as
an argument. If the stack size cannot be set due to system
constraints, an error is reported and the initial stack size is
left unchanged. If undefined, the stack size is system dependent.
_See also_:
*note OMP_STACKSIZE::
_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 this
is 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 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
========================================================================
This seems simple enough for PARALLEL blocks. Create a private struct
for communicating between the 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.
It is not clear 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 trickiness 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/). For 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 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
Preamble
========
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and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom to
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GNU General Public License for most of our software; it applies also to
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When we speak of free software, we are referring to freedom, not
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To protect your rights, we need to prevent others from denying you
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Developers that use the GNU GPL protect your rights with two steps:
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The precise terms and conditions for copying, distribution and
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TERMS AND CONDITIONS
====================
0. Definitions.
"This License" refers to version 3 of the GNU General Public
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"Copyright" also means copyright-like laws that apply to other
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A "covered work" means either the unmodified Program or a work
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To "propagate" a work means to do anything with it that, without
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All rights granted under this License are granted for the term of
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entire Program shall be treated as though they were included in
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that part may be used separately under those permissions, but the
entire Program remains governed by this License without regard to
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Legal Notices displayed by works containing it; or
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the above requirements apply either way.
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You may not propagate or modify a covered work except as expressly
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under this License (including any patent licenses granted under the
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However, if you cease all violation of this License, then your
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9. Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or
run a copy of the Program. Ancillary propagation of a covered work
occurring solely as a consequence of using peer-to-peer
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infringe copyright if you do not accept this License. Therefore,
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10. Automatic Licensing of Downstream Recipients.
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entered into that arrangement, or that patent license was granted,
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Nothing in this License shall be construed as excluding or limiting
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12. No Surrender of Others' Freedom.
If conditions are imposed on you (whether by court order, agreement
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13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
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14. Revised Versions of this License.
The Free Software Foundation may publish revised and/or new
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may differ in detail to address new problems or concerns.
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If the Program specifies that a proxy can decide which future
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15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE
COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS"
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SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR OR CORRECTION.
16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR
DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA
BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF
THE POSSIBILITY OF SUCH DAMAGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided
above cannot be given local legal effect according to their terms,
reviewing courts shall apply local law that most closely
approximates an absolute waiver of all civil liability in
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liability accompanies a copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
===========================
How to Apply These Terms to Your New Programs
=============================================
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least the
"copyright" line and a pointer to where the full notice is found.
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
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper
mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
PROGRAM Copyright (C) YEAR NAME OF AUTHOR
This program comes with ABSOLUTELY NO WARRANTY; for details type 'show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type 'show c' for details.
The hypothetical commands 'show w' and 'show c' should show the
appropriate parts of the General Public License. Of course, your
program's commands might be different; for a GUI interface, you would
use an "about box".
You should also get your employer (if you work as a programmer) or
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. For more information on this, and how to apply and follow
the GNU GPL, see <http://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your
program into proprietary programs. If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library. If this is what you want to do, use the
GNU Lesser General Public License instead of this License. But first,
please read <http://www.gnu.org/philosophy/why-not-lgpl.html>.
File: libgomp.info, Node: GNU Free Documentation License, Next: Funding, Prev: Copying, Up: Top
GNU Free Documentation License
******************************
Version 1.3, 3 November 2008
Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
<http://fsf.org/>
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
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
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
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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
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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
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A "Secondary Section" is a named appendix or a front-matter section
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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
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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
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be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
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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.
The "publisher" means any person or entity that distributes copies
of the Document to the public.
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 under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void,
and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly and
finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.
Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from you
under this License. If your rights have been terminated and not
permanently reinstated, receipt of a copy of some or all of the
same material does not give you any rights to use it.
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. If the Document specifies that a proxy can
decide which future versions of this License can be used, that
proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.
"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
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 1.3
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: Library 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: Library Index, Prev: Funding, Up: Top
Library Index
*************
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