This is libgomp.info, produced by makeinfo version 6.5 from libgomp.texi. Copyright (C) 2006-2019 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 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being "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 Offloading and Multi Processing Runtime Library. END-INFO-DIR-ENTRY This manual documents libgomp, the GNU Offloading and Multi Processing Runtime library. This is the GNU implementation of the OpenMP and OpenACC APIs for parallel and accelerator programming in C/C++ and Fortran. Published by the Free Software Foundation 51 Franklin Street, Fifth Floor Boston, MA 02110-1301 USA Copyright (C) 2006-2019 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 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being "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 Offloading and Multi Processing Runtime Library. This includes the GNU implementation of the OpenMP (https://www.openmp.org) Application Programming Interface (API) for multi-platform shared-memory parallel programming in C/C++ and Fortran, and the GNU implementation of the OpenACC (https://www.openacc.org) Application Programming Interface (API) for offloading of code to accelerator devices in C/C++ and Fortran. Originally, libgomp implemented the GNU OpenMP Runtime Library. Based on this, support for OpenACC and offloading (both OpenACC and OpenMP 4's target construct) has been added later on, and the library's name changed to GNU Offloading and Multi Processing Runtime Library. * Menu: * Enabling OpenMP:: How to enable OpenMP for your applications. * OpenMP Runtime Library Routines: Runtime Library Routines. The OpenMP runtime application programming interface. * OpenMP Environment Variables: Environment Variables. Influencing OpenMP runtime behavior with environment variables. * Enabling OpenACC:: How to enable OpenACC for your applications. * OpenACC Runtime Library Routines:: The OpenACC runtime application programming interface. * OpenACC Environment Variables:: Influencing OpenACC runtime behavior with environment variables. * CUDA Streams Usage:: Notes on the implementation of asynchronous operations. * OpenACC Library Interoperability:: OpenACC library interoperability with the NVIDIA CUBLAS library. * The libgomp ABI:: Notes on the external ABI presented by libgomp. * Reporting Bugs:: How to report bugs in the GNU Offloading and Multi Processing Runtime Library. * 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 (https://www.openmp.org) manual, version 4.5.  File: libgomp.info, Node: Runtime Library Routines, Next: Environment Variables, Prev: Enabling OpenMP, Up: Top 2 OpenMP Runtime Library Routines ********************************* The runtime routines described here are defined by Section 3 of the OpenMP specification in version 4.5. The routines are structured in following three parts: * Menu: Control threads, processors and the parallel environment. They have C linkage, and do not throw exceptions. * omp_get_active_level:: Number of active parallel regions * omp_get_ancestor_thread_num:: Ancestor thread ID * omp_get_cancellation:: Whether cancellation support is enabled * omp_get_default_device:: Get the default device for target regions * 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_task_priority:: Maximum task priority value that can be set * omp_get_max_threads:: Maximum number of threads of parallel region * omp_get_nested:: Nested parallel regions * omp_get_num_devices:: Number of target devices * omp_get_num_procs:: Number of processors online * omp_get_num_teams:: Number of teams * omp_get_num_threads:: Size of the active team * omp_get_proc_bind:: Whether theads may be moved between CPUs * omp_get_schedule:: Obtain the runtime scheduling method * omp_get_team_num:: Get team number * 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_is_initial_device:: Whether executing on the host device * omp_set_default_device:: Set the default device for target regions * 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. * 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. * 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 specification v4.5 (https://www.openmp.org), Section 3.2.20.  File: libgomp.info, Node: omp_get_ancestor_thread_num, Next: omp_get_cancellation, 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 specification v4.5 (https://www.openmp.org), Section 3.2.18.  File: libgomp.info, Node: omp_get_cancellation, Next: omp_get_default_device, Prev: omp_get_ancestor_thread_num, Up: Runtime Library Routines 2.3 'omp_get_cancellation' - Whether cancellation support is enabled ==================================================================== _Description_: This function returns 'true' if cancellation is activated, 'false' otherwise. Here, 'true' and 'false' represent their language-specific counterparts. Unless 'OMP_CANCELLATION' is set true, cancellations are deactivated. _C/C++_: _Prototype_: 'int omp_get_cancellation(void);' _Fortran_: _Interface_: 'logical function omp_get_cancellation()' _See also_: *note OMP_CANCELLATION:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.9.  File: libgomp.info, Node: omp_get_default_device, Next: omp_get_dynamic, Prev: omp_get_cancellation, Up: Runtime Library Routines 2.4 'omp_get_default_device' - Get the default device for target regions ======================================================================== _Description_: Get the default device for target regions without device clause. _C/C++_: _Prototype_: 'int omp_get_default_device(void);' _Fortran_: _Interface_: 'integer function omp_get_default_device()' _See also_: *note OMP_DEFAULT_DEVICE::, *note omp_set_default_device:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.30.  File: libgomp.info, Node: omp_get_dynamic, Next: omp_get_level, Prev: omp_get_default_device, Up: Runtime Library Routines 2.5 '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 specification v4.5 (https://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 2.6 '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 specification v4.5 (https://www.openmp.org), Section 3.2.17.  File: libgomp.info, Node: omp_get_max_active_levels, Next: omp_get_max_task_priority, Prev: omp_get_level, Up: Runtime Library Routines 2.7 '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 specification v4.5 (https://www.openmp.org), Section 3.2.16.  File: libgomp.info, Node: omp_get_max_task_priority, Next: omp_get_max_threads, Prev: omp_get_max_active_levels, Up: Runtime Library Routines 2.8 'omp_get_max_task_priority' - Maximum priority value ======================================================== that can be set for tasks. _Description_: This function obtains the maximum allowed priority number for tasks. _C/C++_ _Prototype_: 'int omp_get_max_task_priority(void);' _Fortran_: _Interface_: 'integer function omp_get_max_task_priority()' _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.29.  File: libgomp.info, Node: omp_get_max_threads, Next: omp_get_nested, Prev: omp_get_max_task_priority, Up: Runtime Library Routines 2.9 '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 specification v4.5 (https://www.openmp.org), Section 3.2.3.  File: libgomp.info, Node: omp_get_nested, Next: omp_get_num_devices, Prev: omp_get_max_threads, Up: Runtime Library Routines 2.10 '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 specification v4.5 (https://www.openmp.org), Section 3.2.11.  File: libgomp.info, Node: omp_get_num_devices, Next: omp_get_num_procs, Prev: omp_get_nested, Up: Runtime Library Routines 2.11 'omp_get_num_devices' - Number of target devices ===================================================== _Description_: Returns the number of target devices. _C/C++_: _Prototype_: 'int omp_get_num_devices(void);' _Fortran_: _Interface_: 'integer function omp_get_num_devices()' _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.31.  File: libgomp.info, Node: omp_get_num_procs, Next: omp_get_num_teams, Prev: omp_get_num_devices, Up: Runtime Library Routines 2.12 'omp_get_num_procs' - Number of processors online ====================================================== _Description_: Returns the number of processors online on that device. _C/C++_: _Prototype_: 'int omp_get_num_procs(void);' _Fortran_: _Interface_: 'integer function omp_get_num_procs()' _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.5.  File: libgomp.info, Node: omp_get_num_teams, Next: omp_get_num_threads, Prev: omp_get_num_procs, Up: Runtime Library Routines 2.13 'omp_get_num_teams' - Number of teams ========================================== _Description_: Returns the number of teams in the current team region. _C/C++_: _Prototype_: 'int omp_get_num_teams(void);' _Fortran_: _Interface_: 'integer function omp_get_num_teams()' _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.32.  File: libgomp.info, Node: omp_get_num_threads, Next: omp_get_proc_bind, Prev: omp_get_num_teams, Up: Runtime Library Routines 2.14 '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 specification v4.5 (https://www.openmp.org), Section 3.2.2.  File: libgomp.info, Node: omp_get_proc_bind, Next: omp_get_schedule, Prev: omp_get_num_threads, Up: Runtime Library Routines 2.15 'omp_get_proc_bind' - Whether theads may be moved between CPUs =================================================================== _Description_: This functions returns the currently active thread affinity policy, which is set via 'OMP_PROC_BIND'. Possible values are 'omp_proc_bind_false', 'omp_proc_bind_true', 'omp_proc_bind_master', 'omp_proc_bind_close' and 'omp_proc_bind_spread'. _C/C++_: _Prototype_: 'omp_proc_bind_t omp_get_proc_bind(void);' _Fortran_: _Interface_: 'integer(kind=omp_proc_bind_kind) function omp_get_proc_bind()' _See also_: *note OMP_PROC_BIND::, *note OMP_PLACES::, *note GOMP_CPU_AFFINITY::, _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.22.  File: libgomp.info, Node: omp_get_schedule, Next: omp_get_team_num, Prev: omp_get_proc_bind, Up: Runtime Library Routines 2.16 '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, CHUNK_SIZE, is set to the chunk size. _C/C++_ _Prototype_: 'void omp_get_schedule(omp_sched_t *kind, int *chunk_size);' _Fortran_: _Interface_: 'subroutine omp_get_schedule(kind, chunk_size)' 'integer(kind=omp_sched_kind) kind' 'integer chunk_size' _See also_: *note omp_set_schedule::, *note OMP_SCHEDULE:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.13.  File: libgomp.info, Node: omp_get_team_num, Next: omp_get_team_size, Prev: omp_get_schedule, Up: Runtime Library Routines 2.17 'omp_get_team_num' - Get team number ========================================= _Description_: Returns the team number of the calling thread. _C/C++_: _Prototype_: 'int omp_get_team_num(void);' _Fortran_: _Interface_: 'integer function omp_get_team_num()' _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.33.  File: libgomp.info, Node: omp_get_team_size, Next: omp_get_thread_limit, Prev: omp_get_team_num, Up: Runtime Library Routines 2.18 '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 specification v4.5 (https://www.openmp.org), Section 3.2.19.  File: libgomp.info, Node: omp_get_thread_limit, Next: omp_get_thread_num, Prev: omp_get_team_size, Up: Runtime Library Routines 2.19 '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 specification v4.5 (https://www.openmp.org), Section 3.2.14.  File: libgomp.info, Node: omp_get_thread_num, Next: omp_in_parallel, Prev: omp_get_thread_limit, Up: Runtime Library Routines 2.20 '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 specification v4.5 (https://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 2.21 '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 specification v4.5 (https://www.openmp.org), Section 3.2.6.  File: libgomp.info, Node: omp_in_final, Next: omp_is_initial_device, Prev: omp_in_parallel, Up: Runtime Library Routines 2.22 '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 specification v4.5 (https://www.openmp.org), Section 3.2.21.  File: libgomp.info, Node: omp_is_initial_device, Next: omp_set_default_device, Prev: omp_in_final, Up: Runtime Library Routines 2.23 'omp_is_initial_device' - Whether executing on the host device =================================================================== _Description_: This function returns 'true' if currently running on the host device, 'false' otherwise. Here, 'true' and 'false' represent their language-specific counterparts. _C/C++_: _Prototype_: 'int omp_is_initial_device(void);' _Fortran_: _Interface_: 'logical function omp_is_initial_device()' _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.34.  File: libgomp.info, Node: omp_set_default_device, Next: omp_set_dynamic, Prev: omp_is_initial_device, Up: Runtime Library Routines 2.24 'omp_set_default_device' - Set the default device for target regions ========================================================================= _Description_: Set the default device for target regions without device clause. The argument shall be a nonnegative device number. _C/C++_: _Prototype_: 'void omp_set_default_device(int device_num);' _Fortran_: _Interface_: 'subroutine omp_set_default_device(device_num)' 'integer device_num' _See also_: *note OMP_DEFAULT_DEVICE::, *note omp_get_default_device:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.29.  File: libgomp.info, Node: omp_set_dynamic, Next: omp_set_max_active_levels, Prev: omp_set_default_device, Up: Runtime Library Routines 2.25 '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 dynamic_threads);' _Fortran_: _Interface_: 'subroutine omp_set_dynamic(dynamic_threads)' 'logical, intent(in) :: dynamic_threads' _See also_: *note OMP_DYNAMIC::, *note omp_get_dynamic:: _Reference_: OpenMP specification v4.5 (https://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 2.26 '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 specification v4.5 (https://www.openmp.org), Section 3.2.15.  File: libgomp.info, Node: omp_set_nested, Next: omp_set_num_threads, Prev: omp_set_max_active_levels, Up: Runtime Library Routines 2.27 '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 nested);' _Fortran_: _Interface_: 'subroutine omp_set_nested(nested)' 'logical, intent(in) :: nested' _See also_: *note OMP_NESTED::, *note omp_get_nested:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.10.  File: libgomp.info, Node: omp_set_num_threads, Next: omp_set_schedule, Prev: omp_set_nested, Up: Runtime Library Routines 2.28 '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 num_threads);' _Fortran_: _Interface_: 'subroutine omp_set_num_threads(num_threads)' 'integer, intent(in) :: num_threads' _See also_: *note OMP_NUM_THREADS::, *note omp_get_num_threads::, *note omp_get_max_threads:: _Reference_: OpenMP specification v4.5 (https://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 2.29 '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 CHUNK_SIZE if positive, or to the default value if zero or negative. For 'omp_sched_auto' the CHUNK_SIZE argument is ignored. _C/C++_ _Prototype_: 'void omp_set_schedule(omp_sched_t kind, int chunk_size);' _Fortran_: _Interface_: 'subroutine omp_set_schedule(kind, chunk_size)' 'integer(kind=omp_sched_kind) kind' 'integer chunk_size' _See also_: *note omp_get_schedule:: *note OMP_SCHEDULE:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.2.12.  File: libgomp.info, Node: omp_init_lock, Next: omp_set_lock, Prev: omp_set_schedule, Up: Runtime Library Routines 2.30 '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(svar)' 'integer(omp_lock_kind), intent(out) :: svar' _See also_: *note omp_destroy_lock:: _Reference_: OpenMP specification v4.5 (https://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 2.31 '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(svar)' 'integer(omp_lock_kind), intent(inout) :: svar' _See also_: *note omp_init_lock::, *note omp_test_lock::, *note omp_unset_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.4.  File: libgomp.info, Node: omp_test_lock, Next: omp_unset_lock, Prev: omp_set_lock, Up: Runtime Library Routines 2.32 '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(svar)' 'integer(omp_lock_kind), intent(inout) :: svar' _See also_: *note omp_init_lock::, *note omp_set_lock::, *note omp_set_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.6.  File: libgomp.info, Node: omp_unset_lock, Next: omp_destroy_lock, Prev: omp_test_lock, Up: Runtime Library Routines 2.33 '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(svar)' 'integer(omp_lock_kind), intent(inout) :: svar' _See also_: *note omp_set_lock::, *note omp_test_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.5.  File: libgomp.info, Node: omp_destroy_lock, Next: omp_init_nest_lock, Prev: omp_unset_lock, Up: Runtime Library Routines 2.34 '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(svar)' 'integer(omp_lock_kind), intent(inout) :: svar' _See also_: *note omp_init_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.3.  File: libgomp.info, Node: omp_init_nest_lock, Next: omp_set_nest_lock, Prev: omp_destroy_lock, Up: Runtime Library Routines 2.35 '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(nvar)' 'integer(omp_nest_lock_kind), intent(out) :: nvar' _See also_: *note omp_destroy_nest_lock:: _Reference_: OpenMP specification v4.5 (https://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 2.36 '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(nvar)' 'integer(omp_nest_lock_kind), intent(inout) :: nvar' _See also_: *note omp_init_nest_lock::, *note omp_unset_nest_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.4.  File: libgomp.info, Node: omp_test_nest_lock, Next: omp_unset_nest_lock, Prev: omp_set_nest_lock, Up: Runtime Library Routines 2.37 '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(nvar)' 'integer(omp_nest_lock_kind), intent(inout) :: nvar' _See also_: *note omp_init_lock::, *note omp_set_lock::, *note omp_set_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.6.  File: libgomp.info, Node: omp_unset_nest_lock, Next: omp_destroy_nest_lock, Prev: omp_test_nest_lock, Up: Runtime Library Routines 2.38 '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(nvar)' 'integer(omp_nest_lock_kind), intent(inout) :: nvar' _See also_: *note omp_set_nest_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.5.  File: libgomp.info, Node: omp_destroy_nest_lock, Next: omp_get_wtick, Prev: omp_unset_nest_lock, Up: Runtime Library Routines 2.39 '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(nvar)' 'integer(omp_nest_lock_kind), intent(inout) :: nvar' _See also_: *note omp_init_lock:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 3.3.3.  File: libgomp.info, Node: omp_get_wtick, Next: omp_get_wtime, Prev: omp_destroy_nest_lock, Up: Runtime Library Routines 2.40 '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 specification v4.5 (https://www.openmp.org), Section 3.4.2.  File: libgomp.info, Node: omp_get_wtime, Prev: omp_get_wtick, Up: Runtime Library Routines 2.41 '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 specification v4.5 (https://www.openmp.org), Section 3.4.1.  File: libgomp.info, Node: Environment Variables, Next: Enabling OpenACC, Prev: Runtime Library Routines, Up: Top 3 OpenMP Environment Variables ****************************** The environment variables which beginning with 'OMP_' are defined by section 4 of the OpenMP specification in version 4.5, while those beginning with 'GOMP_' are GNU extensions. * Menu: * OMP_CANCELLATION:: Set whether cancellation is activated * OMP_DISPLAY_ENV:: Show OpenMP version and environment variables * OMP_DEFAULT_DEVICE:: Set the device used in target regions * OMP_DYNAMIC:: Dynamic adjustment of threads * OMP_MAX_ACTIVE_LEVELS:: Set the maximum number of nested parallel regions * OMP_MAX_TASK_PRIORITY:: Set the maximum task priority value * OMP_NESTED:: Nested parallel regions * OMP_NUM_THREADS:: Specifies the number of threads to use * OMP_PROC_BIND:: Whether theads may be moved between CPUs * OMP_PLACES:: Specifies on which CPUs the theads should be placed * 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 * GOMP_CPU_AFFINITY:: Bind threads to specific CPUs * GOMP_DEBUG:: Enable debugging output * GOMP_STACKSIZE:: Set default thread stack size * GOMP_SPINCOUNT:: Set the busy-wait spin count * GOMP_RTEMS_THREAD_POOLS:: Set the RTEMS specific thread pools  File: libgomp.info, Node: OMP_CANCELLATION, Next: OMP_DISPLAY_ENV, Up: Environment Variables 3.1 'OMP_CANCELLATION' - Set whether cancellation is activated ============================================================== _Description_: If set to 'TRUE', the cancellation is activated. If set to 'FALSE' or if unset, cancellation is disabled and the 'cancel' construct is ignored. _See also_: *note omp_get_cancellation:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.11  File: libgomp.info, Node: OMP_DISPLAY_ENV, Next: OMP_DEFAULT_DEVICE, Prev: OMP_CANCELLATION, Up: Environment Variables 3.2 'OMP_DISPLAY_ENV' - Show OpenMP version and environment variables ===================================================================== _Description_: If set to 'TRUE', the OpenMP version number and the values associated with the OpenMP environment variables are printed to 'stderr'. If set to 'VERBOSE', it additionally shows the value of the environment variables which are GNU extensions. If undefined or set to 'FALSE', this information will not be shown. _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.12  File: libgomp.info, Node: OMP_DEFAULT_DEVICE, Next: OMP_DYNAMIC, Prev: OMP_DISPLAY_ENV, Up: Environment Variables 3.3 'OMP_DEFAULT_DEVICE' - Set the device used in target regions ================================================================ _Description_: Set to choose the device which is used in a 'target' region, unless the value is overridden by 'omp_set_default_device' or by a 'device' clause. The value shall be the nonnegative device number. If no device with the given device number exists, the code is executed on the host. If unset, device number 0 will be used. _See also_: *note omp_get_default_device::, *note omp_set_default_device::, _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.13  File: libgomp.info, Node: OMP_DYNAMIC, Next: OMP_MAX_ACTIVE_LEVELS, Prev: OMP_DEFAULT_DEVICE, Up: Environment Variables 3.4 '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 specification v4.5 (https://www.openmp.org), Section 4.3  File: libgomp.info, Node: OMP_MAX_ACTIVE_LEVELS, Next: OMP_MAX_TASK_PRIORITY, Prev: OMP_DYNAMIC, Up: Environment Variables 3.5 '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 specification v4.5 (https://www.openmp.org), Section 4.9  File: libgomp.info, Node: OMP_MAX_TASK_PRIORITY, Next: OMP_NESTED, Prev: OMP_MAX_ACTIVE_LEVELS, Up: Environment Variables 3.6 'OMP_MAX_TASK_PRIORITY' - Set the maximum priority ====================================================== number that can be set for a task. _Description_: Specifies the initial value for the maximum priority value that can be set for a task. The value of this variable shall be a non-negative integer, and zero is allowed. If undefined, the default priority is 0. _See also_: *note omp_get_max_task_priority:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.14  File: libgomp.info, Node: OMP_NESTED, Next: OMP_NUM_THREADS, Prev: OMP_MAX_TASK_PRIORITY, Up: Environment Variables 3.7 '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 specification v4.5 (https://www.openmp.org), Section 4.6  File: libgomp.info, Node: OMP_NUM_THREADS, Next: OMP_PROC_BIND, Prev: OMP_NESTED, Up: Environment Variables 3.8 '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 specification v4.5 (https://www.openmp.org), Section 4.2  File: libgomp.info, Node: OMP_PROC_BIND, Next: OMP_PLACES, Prev: OMP_NUM_THREADS, 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. Alternatively, a comma separated list with the values 'MASTER', 'CLOSE' and 'SPREAD' can be used to specify the thread affinity policy for the corresponding nesting level. With 'MASTER' the worker threads are in the same place partition as the master thread. With 'CLOSE' those are kept close to the master thread in contiguous place partitions. And with 'SPREAD' a sparse distribution across the place partitions is used. When undefined, 'OMP_PROC_BIND' defaults to 'TRUE' when 'OMP_PLACES' or 'GOMP_CPU_AFFINITY' is set and 'FALSE' otherwise. _See also_: *note OMP_PLACES::, *note GOMP_CPU_AFFINITY::, *note omp_get_proc_bind:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.4  File: libgomp.info, Node: OMP_PLACES, Next: OMP_STACKSIZE, Prev: OMP_PROC_BIND, Up: Environment Variables 3.10 'OMP_PLACES' - Specifies on which CPUs the theads should be placed ======================================================================= _Description_: The thread placement can be either specified using an abstract name or by an explicit list of the places. The abstract names 'threads', 'cores' and 'sockets' can be optionally followed by a positive number in parentheses, which denotes the how many places shall be created. With 'threads' each place corresponds to a single hardware thread; 'cores' to a single core with the corresponding number of hardware threads; and with 'sockets' the place corresponds to a single socket. The resulting placement can be shown by setting the 'OMP_DISPLAY_ENV' environment variable. Alternatively, the placement can be specified explicitly as comma-separated list of places. A place is specified by set of nonnegative numbers in curly braces, denoting the denoting the hardware threads. The hardware threads belonging to a place can either be specified as comma-separated list of nonnegative thread numbers or using an interval. Multiple places can also be either specified by a comma-separated list of places or by an interval. To specify an interval, a colon followed by the count is placed after after the hardware thread number or the place. Optionally, the length can be followed by a colon and the stride number - otherwise a unit stride is assumed. For instance, the following specifies the same places list: '"{0,1,2}, {3,4,6}, {7,8,9}, {10,11,12}"'; '"{0:3}, {3:3}, {7:3}, {10:3}"'; and '"{0:2}:4:3"'. If 'OMP_PLACES' and 'GOMP_CPU_AFFINITY' are unset and 'OMP_PROC_BIND' is either unset or 'false', threads may be moved between CPUs following no placement policy. _See also_: *note OMP_PROC_BIND::, *note GOMP_CPU_AFFINITY::, *note omp_get_proc_bind::, *note OMP_DISPLAY_ENV:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.5  File: libgomp.info, Node: OMP_STACKSIZE, Next: OMP_SCHEDULE, Prev: OMP_PLACES, Up: Environment Variables 3.11 '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 specification v4.5 (https://www.openmp.org), Section 4.7  File: libgomp.info, Node: OMP_SCHEDULE, Next: OMP_THREAD_LIMIT, Prev: OMP_STACKSIZE, Up: Environment Variables 3.12 '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 specification v4.5 (https://www.openmp.org), Sections 2.7.1.1 and 4.1  File: libgomp.info, Node: OMP_THREAD_LIMIT, Next: OMP_WAIT_POLICY, Prev: OMP_SCHEDULE, Up: Environment Variables 3.13 '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 specification v4.5 (https://www.openmp.org), Section 4.10  File: libgomp.info, Node: OMP_WAIT_POLICY, Next: GOMP_CPU_AFFINITY, Prev: OMP_THREAD_LIMIT, Up: Environment Variables 3.14 '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. If undefined, threads wait actively for a short time before waiting passively. _See also_: *note GOMP_SPINCOUNT:: _Reference_: OpenMP specification v4.5 (https://www.openmp.org), Section 4.8  File: libgomp.info, Node: GOMP_CPU_AFFINITY, Next: GOMP_DEBUG, Prev: OMP_WAIT_POLICY, Up: Environment Variables 3.15 '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 libgomp 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 both 'GOMP_CPU_AFFINITY' and 'OMP_PROC_BIND' are set, 'OMP_PROC_BIND' has a higher precedence. If neither has been set and 'OMP_PROC_BIND' is unset, or when 'OMP_PROC_BIND' is set to 'FALSE', the host system will handle the assignment of threads to CPUs. _See also_: *note OMP_PLACES::, *note OMP_PROC_BIND::  File: libgomp.info, Node: GOMP_DEBUG, Next: GOMP_STACKSIZE, Prev: GOMP_CPU_AFFINITY, Up: Environment Variables 3.16 'GOMP_DEBUG' - Enable debugging output =========================================== _Description_: Enable debugging output. The variable should be set to '0' (disabled, also the default if not set), or '1' (enabled). If enabled, some debugging output will be printed during execution. This is currently not specified in more detail, and subject to change.  File: libgomp.info, Node: GOMP_STACKSIZE, Next: GOMP_SPINCOUNT, Prev: GOMP_DEBUG, Up: Environment Variables 3.17 '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: GOMP_SPINCOUNT, Next: GOMP_RTEMS_THREAD_POOLS, Prev: GOMP_STACKSIZE, Up: Environment Variables 3.18 'GOMP_SPINCOUNT' - Set the busy-wait spin count ==================================================== _Description_: Determines how long a threads waits actively with consuming CPU power before waiting passively without consuming CPU power. The value may be either 'INFINITE', 'INFINITY' to always wait actively or an integer which gives the number of spins of the busy-wait loop. The integer may optionally be followed by the following suffixes acting as multiplication factors: 'k' (kilo, thousand), 'M' (mega, million), 'G' (giga, billion), or 'T' (tera, trillion). If undefined, 0 is used when 'OMP_WAIT_POLICY' is 'PASSIVE', 300,000 is used when 'OMP_WAIT_POLICY' is undefined and 30 billion is used when 'OMP_WAIT_POLICY' is 'ACTIVE'. If there are more OpenMP threads than available CPUs, 1000 and 100 spins are used for 'OMP_WAIT_POLICY' being 'ACTIVE' or undefined, respectively; unless the 'GOMP_SPINCOUNT' is lower or 'OMP_WAIT_POLICY' is 'PASSIVE'. _See also_: *note OMP_WAIT_POLICY::  File: libgomp.info, Node: GOMP_RTEMS_THREAD_POOLS, Prev: GOMP_SPINCOUNT, Up: Environment Variables 3.19 'GOMP_RTEMS_THREAD_POOLS' - Set the RTEMS specific thread pools ==================================================================== _Description_: This environment variable is only used on the RTEMS real-time operating system. It determines the scheduler instance specific thread pools. The format for 'GOMP_RTEMS_THREAD_POOLS' is a list of optional '[$]@' configurations separated by ':' where: * '' is the thread pool count for this scheduler instance. * '$' is an optional priority for the worker threads of a thread pool according to 'pthread_setschedparam'. In case a priority value is omitted, then a worker thread will inherit the priority of the OpenMP master thread that created it. The priority of the worker thread is not changed after creation, even if a new OpenMP master thread using the worker has a different priority. * '@' is the scheduler instance name according to the RTEMS application configuration. In case no thread pool configuration is specified for a scheduler instance, then each OpenMP master thread of this scheduler instance will use its own dynamically allocated thread pool. To limit the worker thread count of the thread pools, each OpenMP master thread must call 'omp_set_num_threads'. _Example_: Lets suppose we have three scheduler instances 'IO', 'WRK0', and 'WRK1' with 'GOMP_RTEMS_THREAD_POOLS' set to '"1@WRK0:3$4@WRK1"'. Then there are no thread pool restrictions for scheduler instance 'IO'. In the scheduler instance 'WRK0' there is one thread pool available. Since no priority is specified for this scheduler instance, the worker thread inherits the priority of the OpenMP master thread that created it. In the scheduler instance 'WRK1' there are three thread pools available and their worker threads run at priority four.  File: libgomp.info, Node: Enabling OpenACC, Next: OpenACC Runtime Library Routines, Prev: Environment Variables, Up: Top 4 Enabling OpenACC ****************** To activate the OpenACC extensions for C/C++ and Fortran, the compile-time flag '-fopenacc' must be specified. This enables the OpenACC directive '#pragma acc' in C/C++ and '!$accp' directives in free form, 'c$acc', '*$acc' and '!$acc' directives in fixed form, '!$' conditional compilation sentinels in free form and 'c$', '*$' and '!$' sentinels in fixed form, for Fortran. The flag also arranges for automatic linking of the OpenACC runtime library (*note OpenACC Runtime Library Routines::). A complete description of all OpenACC directives accepted may be found in the OpenACC (https://www.openacc.org) Application Programming Interface manual, version 2.0. Note that this is an experimental feature and subject to change in future versions of GCC. See for more information.  File: libgomp.info, Node: OpenACC Runtime Library Routines, Next: OpenACC Environment Variables, Prev: Enabling OpenACC, Up: Top 5 OpenACC Runtime Library Routines ********************************** The runtime routines described here are defined by section 3 of the OpenACC specifications in version 2.0. They have C linkage, and do not throw exceptions. Generally, they are available only for the host, with the exception of 'acc_on_device', which is available for both the host and the acceleration device. * Menu: * acc_get_num_devices:: Get number of devices for the given device type. * acc_set_device_type:: Set type of device accelerator to use. * acc_get_device_type:: Get type of device accelerator to be used. * acc_set_device_num:: Set device number to use. * acc_get_device_num:: Get device number to be used. * acc_async_test:: Tests for completion of a specific asynchronous operation. * acc_async_test_all:: Tests for completion of all asychronous operations. * acc_wait:: Wait for completion of a specific asynchronous operation. * acc_wait_all:: Waits for completion of all asyncrhonous operations. * acc_wait_all_async:: Wait for completion of all asynchronous operations. * acc_wait_async:: Wait for completion of asynchronous operations. * acc_init:: Initialize runtime for a specific device type. * acc_shutdown:: Shuts down the runtime for a specific device type. * acc_on_device:: Whether executing on a particular device * acc_malloc:: Allocate device memory. * acc_free:: Free device memory. * acc_copyin:: Allocate device memory and copy host memory to it. * acc_present_or_copyin:: If the data is not present on the device, allocate device memory and copy from host memory. * acc_create:: Allocate device memory and map it to host memory. * acc_present_or_create:: If the data is not present on the device, allocate device memory and map it to host memory. * acc_copyout:: Copy device memory to host memory. * acc_delete:: Free device memory. * acc_update_device:: Update device memory from mapped host memory. * acc_update_self:: Update host memory from mapped device memory. * acc_map_data:: Map previously allocated device memory to host memory. * acc_unmap_data:: Unmap device memory from host memory. * acc_deviceptr:: Get device pointer associated with specific host address. * acc_hostptr:: Get host pointer associated with specific device address. * acc_is_present:: Indiciate whether host variable / array is present on device. * acc_memcpy_to_device:: Copy host memory to device memory. * acc_memcpy_from_device:: Copy device memory to host memory. API routines for target platforms. * acc_get_current_cuda_device:: Get CUDA device handle. * acc_get_current_cuda_context::Get CUDA context handle. * acc_get_cuda_stream:: Get CUDA stream handle. * acc_set_cuda_stream:: Set CUDA stream handle.  File: libgomp.info, Node: acc_get_num_devices, Next: acc_set_device_type, Up: OpenACC Runtime Library Routines 5.1 'acc_get_num_devices' - Get number of devices for given device type ======================================================================= _Description_ This function returns a value indicating the number of devices available for the device type specified in DEVICETYPE. _C/C++_: _Prototype_: 'int acc_get_num_devices(acc_device_t devicetype);' _Fortran_: _Interface_: 'integer function acc_get_num_devices(devicetype)' 'integer(kind=acc_device_kind) devicetype' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.1.  File: libgomp.info, Node: acc_set_device_type, Next: acc_get_device_type, Prev: acc_get_num_devices, Up: OpenACC Runtime Library Routines 5.2 'acc_set_device_type' - Set type of device accelerator to use. ================================================================== _Description_ This function indicates to the runtime library which device typr, specified in DEVICETYPE, to use when executing a parallel or kernels region. _C/C++_: _Prototype_: 'acc_set_device_type(acc_device_t devicetype);' _Fortran_: _Interface_: 'subroutine acc_set_device_type(devicetype)' 'integer(kind=acc_device_kind) devicetype' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.2.  File: libgomp.info, Node: acc_get_device_type, Next: acc_set_device_num, Prev: acc_set_device_type, Up: OpenACC Runtime Library Routines 5.3 'acc_get_device_type' - Get type of device accelerator to be used. ====================================================================== _Description_ This function returns what device type will be used when executing a parallel or kernels region. _C/C++_: _Prototype_: 'acc_device_t acc_get_device_type(void);' _Fortran_: _Interface_: 'function acc_get_device_type(void)' 'integer(kind=acc_device_kind) acc_get_device_type' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.3.  File: libgomp.info, Node: acc_set_device_num, Next: acc_get_device_num, Prev: acc_get_device_type, Up: OpenACC Runtime Library Routines 5.4 'acc_set_device_num' - Set device number to use. ==================================================== _Description_ This function will indicate to the runtime which device number, specified by NUM, associated with the specifed device type DEVICETYPE. _C/C++_: _Prototype_: 'acc_set_device_num(int num, acc_device_t devicetype);' _Fortran_: _Interface_: 'subroutine acc_set_device_num(devicenum, devicetype)' 'integer devicenum' 'integer(kind=acc_device_kind) devicetype' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.4.  File: libgomp.info, Node: acc_get_device_num, Next: acc_async_test, Prev: acc_set_device_num, Up: OpenACC Runtime Library Routines 5.5 'acc_get_device_num' - Get device number to be used. ======================================================== _Description_ This function returns which device number associated with the specified device type DEVICETYPE, will be used when executing a parallel or kernels region. _C/C++_: _Prototype_: 'int acc_get_device_num(acc_device_t devicetype);' _Fortran_: _Interface_: 'function acc_get_device_num(devicetype)' 'integer(kind=acc_device_kind) devicetype' 'integer acc_get_device_num' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.5.  File: libgomp.info, Node: acc_async_test, Next: acc_async_test_all, Prev: acc_get_device_num, Up: OpenACC Runtime Library Routines 5.6 'acc_async_test' - Test for completion of a specific asynchronous operation. ================================================================================ _Description_ This function tests for completion of the asynchrounous operation specified in ARG. In C/C++, a non-zero value will be returned to indicate the specified asynchronous operation has completed. While Fortran will return a 'true'. If the asynchrounous operation has not completed, C/C++ returns a zero and Fortran returns a 'false'. _C/C++_: _Prototype_: 'int acc_async_test(int arg);' _Fortran_: _Interface_: 'function acc_async_test(arg)' 'integer(kind=acc_handle_kind) arg' 'logical acc_async_test' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.6.  File: libgomp.info, Node: acc_async_test_all, Next: acc_wait, Prev: acc_async_test, Up: OpenACC Runtime Library Routines 5.7 'acc_async_test_all' - Tests for completion of all asynchronous operations. =============================================================================== _Description_ This function tests for completion of all asynchrounous operations. In C/C++, a non-zero value will be returned to indicate all asynchronous operations have completed. While Fortran will return a 'true'. If any asynchronous operation has not completed, C/C++ returns a zero and Fortran returns a 'false'. _C/C++_: _Prototype_: 'int acc_async_test_all(void);' _Fortran_: _Interface_: 'function acc_async_test()' 'logical acc_get_device_num' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.7.  File: libgomp.info, Node: acc_wait, Next: acc_wait_all, Prev: acc_async_test_all, Up: OpenACC Runtime Library Routines 5.8 'acc_wait' - Wait for completion of a specific asynchronous operation. ========================================================================== _Description_ This function waits for completion of the asynchronous operation specified in ARG. _C/C++_: _Prototype_: 'acc_wait(arg);' _Prototype 'acc_async_wait(arg);' (OpenACC 1.0 compatibility)_: _Fortran_: _Interface_: 'subroutine acc_wait(arg)' 'integer(acc_handle_kind) arg' _Interface 'subroutine acc_async_wait(arg)' (OpenACC 1.0 compatibility)_: 'integer(acc_handle_kind) arg' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.8.  File: libgomp.info, Node: acc_wait_all, Next: acc_wait_all_async, Prev: acc_wait, Up: OpenACC Runtime Library Routines 5.9 'acc_wait_all' - Waits for completion of all asynchronous operations. ========================================================================= _Description_ This function waits for the completion of all asynchronous operations. _C/C++_: _Prototype_: 'acc_wait_all(void);' _Prototype 'acc_async_wait_all(void);' (OpenACC 1.0 compatibility)_: _Fortran_: _Interface_: 'subroutine acc_wait_all()' _Interface 'subroutine acc_async_wait_all()' (OpenACC 1.0 compatibility)_: _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.10.  File: libgomp.info, Node: acc_wait_all_async, Next: acc_wait_async, Prev: acc_wait_all, Up: OpenACC Runtime Library Routines 5.10 'acc_wait_all_async' - Wait for completion of all asynchronous operations. =============================================================================== _Description_ This function enqueues a wait operation on the queue ASYNC for any and all asynchronous operations that have been previously enqueued on any queue. _C/C++_: _Prototype_: 'acc_wait_all_async(int async);' _Fortran_: _Interface_: 'subroutine acc_wait_all_async(async)' 'integer(acc_handle_kind) async' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.11.  File: libgomp.info, Node: acc_wait_async, Next: acc_init, Prev: acc_wait_all_async, Up: OpenACC Runtime Library Routines 5.11 'acc_wait_async' - Wait for completion of asynchronous operations. ======================================================================= _Description_ This function enqueues a wait operation on queue ASYNC for any and all asynchronous operations enqueued on queue ARG. _C/C++_: _Prototype_: 'acc_wait_async(int arg, int async);' _Fortran_: _Interface_: 'subroutine acc_wait_async(arg, async)' 'integer(acc_handle_kind) arg, async' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.9.  File: libgomp.info, Node: acc_init, Next: acc_shutdown, Prev: acc_wait_async, Up: OpenACC Runtime Library Routines 5.12 'acc_init' - Initialize runtime for a specific device type. ================================================================ _Description_ This function initializes the runtime for the device type specified in DEVICETYPE. _C/C++_: _Prototype_: 'acc_init(acc_device_t devicetype);' _Fortran_: _Interface_: 'subroutine acc_init(devicetype)' 'integer(acc_device_kind) devicetype' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.12.  File: libgomp.info, Node: acc_shutdown, Next: acc_on_device, Prev: acc_init, Up: OpenACC Runtime Library Routines 5.13 'acc_shutdown' - Shuts down the runtime for a specific device type. ======================================================================== _Description_ This function shuts down the runtime for the device type specified in DEVICETYPE. _C/C++_: _Prototype_: 'acc_shutdown(acc_device_t devicetype);' _Fortran_: _Interface_: 'subroutine acc_shutdown(devicetype)' 'integer(acc_device_kind) devicetype' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.13.  File: libgomp.info, Node: acc_on_device, Next: acc_malloc, Prev: acc_shutdown, Up: OpenACC Runtime Library Routines 5.14 'acc_on_device' - Whether executing on a particular device =============================================================== _Description_: This function returns whether the program is executing on a particular device specified in DEVICETYPE. In C/C++ a non-zero value is returned to indicate the device is execiting on the specified device type. In Fortran, 'true' will be returned. If the program is not executing on the specified device type C/C++ will return a zero, while Fortran will return 'false'. _C/C++_: _Prototype_: 'acc_on_device(acc_device_t devicetype);' _Fortran_: _Interface_: 'function acc_on_device(devicetype)' 'integer(acc_device_kind) devicetype' 'logical acc_on_device' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.14.  File: libgomp.info, Node: acc_malloc, Next: acc_free, Prev: acc_on_device, Up: OpenACC Runtime Library Routines 5.15 'acc_malloc' - Allocate device memory. =========================================== _Description_ This function allocates LEN bytes of device memory. It returns the device address of the allocated memory. _C/C++_: _Prototype_: 'd_void* acc_malloc(size_t len);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.15.  File: libgomp.info, Node: acc_free, Next: acc_copyin, Prev: acc_malloc, Up: OpenACC Runtime Library Routines 5.16 'acc_free' - Free device memory. ===================================== _Description_ Free previously allocated device memory at the device address 'a'. _C/C++_: _Prototype_: 'acc_free(d_void *a);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.16.  File: libgomp.info, Node: acc_copyin, Next: acc_present_or_copyin, Prev: acc_free, Up: OpenACC Runtime Library Routines 5.17 'acc_copyin' - Allocate device memory and copy host memory to it. ====================================================================== _Description_ In C/C++, this function allocates LEN bytes of device memory and maps it to the specified host address in A. The device address of the newly allocated device memory is returned. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'void *acc_copyin(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_copyin(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_copyin(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.17.  File: libgomp.info, Node: acc_present_or_copyin, Next: acc_create, Prev: acc_copyin, Up: OpenACC Runtime Library Routines 5.18 'acc_present_or_copyin' - If the data is not present on the device, allocate device memory and copy from host memory. ========================================================================================================================== _Description_ This function tests if the host data specifed by A and of length LEN is present or not. If it is not present, then device memory will be allocated and the host memory copied. The device address of the newly allocated device memory is returned. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'void *acc_present_or_copyin(h_void *a, size_t len);' _Prototype_: 'void *acc_pcopyin(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_present_or_copyin(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_present_or_copyin(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Interface_: 'subroutine acc_pcopyin(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_pcopyin(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.18.  File: libgomp.info, Node: acc_create, Next: acc_present_or_create, Prev: acc_present_or_copyin, Up: OpenACC Runtime Library Routines 5.19 'acc_create' - Allocate device memory and map it to host memory. ===================================================================== _Description_ This function allocates device memory and maps it to host memory specified by the host address A with a length of LEN bytes. In C/C++, the function returns the device address of the allocated device memory. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'void *acc_create(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_create(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_create(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.19.  File: libgomp.info, Node: acc_present_or_create, Next: acc_copyout, Prev: acc_create, Up: OpenACC Runtime Library Routines 5.20 'acc_present_or_create' - If the data is not present on the device, allocate device memory and map it to host memory. ========================================================================================================================== _Description_ This function tests if the host data specifed by A and of length LEN is present or not. If it is not present, then device memory will be allocated and mapped to host memory. In C/C++, the device address of the newly allocated device memory is returned. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'void *acc_present_or_create(h_void *a, size_t len)' _Prototype_: 'void *acc_pcreate(h_void *a, size_t len)' _Fortran_: _Interface_: 'subroutine acc_present_or_create(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_present_or_create(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Interface_: 'subroutine acc_pcreate(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_pcreate(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.20.  File: libgomp.info, Node: acc_copyout, Next: acc_delete, Prev: acc_present_or_create, Up: OpenACC Runtime Library Routines 5.21 'acc_copyout' - Copy device memory to host memory. ======================================================= _Description_ This function copies mapped device memory to host memory which is specified by host address A for a length LEN bytes in C/C++. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'acc_copyout(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_copyout(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_copyout(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.21.  File: libgomp.info, Node: acc_delete, Next: acc_update_device, Prev: acc_copyout, Up: OpenACC Runtime Library Routines 5.22 'acc_delete' - Free device memory. ======================================= _Description_ This function frees previously allocated device memory specified by the device address A and the length of LEN bytes. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'acc_delete(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_delete(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_delete(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.22.  File: libgomp.info, Node: acc_update_device, Next: acc_update_self, Prev: acc_delete, Up: OpenACC Runtime Library Routines 5.23 'acc_update_device' - Update device memory from mapped host memory. ======================================================================== _Description_ This function updates the device copy from the previously mapped host memory. The host memory is specified with the host address A and a length of LEN bytes. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'acc_update_device(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_update_device(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_update_device(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.23.  File: libgomp.info, Node: acc_update_self, Next: acc_map_data, Prev: acc_update_device, Up: OpenACC Runtime Library Routines 5.24 'acc_update_self' - Update host memory from mapped device memory. ====================================================================== _Description_ This function updates the host copy from the previously mapped device memory. The host memory is specified with the host address A and a length of LEN bytes. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. _C/C++_: _Prototype_: 'acc_update_self(h_void *a, size_t len);' _Fortran_: _Interface_: 'subroutine acc_update_self(a)' 'type, dimension(:[,:]...) :: a' _Interface_: 'subroutine acc_update_self(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.24.  File: libgomp.info, Node: acc_map_data, Next: acc_unmap_data, Prev: acc_update_self, Up: OpenACC Runtime Library Routines 5.25 'acc_map_data' - Map previously allocated device memory to host memory. ============================================================================ _Description_ This function maps previously allocated device and host memory. The device memory is specified with the device address D. The host memory is specified with the host address H and a length of LEN. _C/C++_: _Prototype_: 'acc_map_data(h_void *h, d_void *d, size_t len);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.25.  File: libgomp.info, Node: acc_unmap_data, Next: acc_deviceptr, Prev: acc_map_data, Up: OpenACC Runtime Library Routines 5.26 'acc_unmap_data' - Unmap device memory from host memory. ============================================================= _Description_ This function unmaps previously mapped device and host memory. The latter specified by H. _C/C++_: _Prototype_: 'acc_unmap_data(h_void *h);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.26.  File: libgomp.info, Node: acc_deviceptr, Next: acc_hostptr, Prev: acc_unmap_data, Up: OpenACC Runtime Library Routines 5.27 'acc_deviceptr' - Get device pointer associated with specific host address. ================================================================================ _Description_ This function returns the device address that has been mapped to the host address specified by H. _C/C++_: _Prototype_: 'void *acc_deviceptr(h_void *h);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.27.  File: libgomp.info, Node: acc_hostptr, Next: acc_is_present, Prev: acc_deviceptr, Up: OpenACC Runtime Library Routines 5.28 'acc_hostptr' - Get host pointer associated with specific device address. ============================================================================== _Description_ This function returns the host address that has been mapped to the device address specified by D. _C/C++_: _Prototype_: 'void *acc_hostptr(d_void *d);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.28.  File: libgomp.info, Node: acc_is_present, Next: acc_memcpy_to_device, Prev: acc_hostptr, Up: OpenACC Runtime Library Routines 5.29 'acc_is_present' - Indicate whether host variable / array is present on device. ==================================================================================== _Description_ This function indicates whether the specified host address in A and a length of LEN bytes is present on the device. In C/C++, a non-zero value is returned to indicate the presence of the mapped memory on the device. A zero is returned to indicate the memory is not mapped on the device. In Fortran, two (2) forms are supported. In the first form, A specifies a contiguous array section. The second form A specifies a variable or array element and LEN specifies the length in bytes. If the host memory is mapped to device memory, then a 'true' is returned. Otherwise, a 'false' is return to indicate the mapped memory is not present. _C/C++_: _Prototype_: 'int acc_is_present(h_void *a, size_t len);' _Fortran_: _Interface_: 'function acc_is_present(a)' 'type, dimension(:[,:]...) :: a' 'logical acc_is_present' _Interface_: 'function acc_is_present(a, len)' 'type, dimension(:[,:]...) :: a' 'integer len' 'logical acc_is_present' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.29.  File: libgomp.info, Node: acc_memcpy_to_device, Next: acc_memcpy_from_device, Prev: acc_is_present, Up: OpenACC Runtime Library Routines 5.30 'acc_memcpy_to_device' - Copy host memory to device memory. ================================================================ _Description_ This function copies host memory specified by host address of SRC to device memory specified by the device address DEST for a length of BYTES bytes. _C/C++_: _Prototype_: 'acc_memcpy_to_device(d_void *dest, h_void *src, size_t bytes);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.30.  File: libgomp.info, Node: acc_memcpy_from_device, Next: acc_get_current_cuda_device, Prev: acc_memcpy_to_device, Up: OpenACC Runtime Library Routines 5.31 'acc_memcpy_from_device' - Copy device memory to host memory. ================================================================== _Description_ This function copies host memory specified by host address of SRC from device memory specified by the device address DEST for a length of BYTES bytes. _C/C++_: _Prototype_: 'acc_memcpy_from_device(d_void *dest, h_void *src, size_t bytes);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 3.2.31.  File: libgomp.info, Node: acc_get_current_cuda_device, Next: acc_get_current_cuda_context, Prev: acc_memcpy_from_device, Up: OpenACC Runtime Library Routines 5.32 'acc_get_current_cuda_device' - Get CUDA device handle. ============================================================ _Description_ This function returns the CUDA device handle. This handle is the same as used by the CUDA Runtime or Driver API's. _C/C++_: _Prototype_: 'void *acc_get_current_cuda_device(void);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section A.2.1.1.  File: libgomp.info, Node: acc_get_current_cuda_context, Next: acc_get_cuda_stream, Prev: acc_get_current_cuda_device, Up: OpenACC Runtime Library Routines 5.33 'acc_get_current_cuda_context' - Get CUDA context handle. ============================================================== _Description_ This function returns the CUDA context handle. This handle is the same as used by the CUDA Runtime or Driver API's. _C/C++_: _Prototype_: 'void *acc_get_current_cuda_context(void);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section A.2.1.2.  File: libgomp.info, Node: acc_get_cuda_stream, Next: acc_set_cuda_stream, Prev: acc_get_current_cuda_context, Up: OpenACC Runtime Library Routines 5.34 'acc_get_cuda_stream' - Get CUDA stream handle. ==================================================== _Description_ This function returns the CUDA stream handle for the queue ASYNC. This handle is the same as used by the CUDA Runtime or Driver API's. _C/C++_: _Prototype_: 'void *acc_get_cuda_stream(int async);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section A.2.1.3.  File: libgomp.info, Node: acc_set_cuda_stream, Prev: acc_get_cuda_stream, Up: OpenACC Runtime Library Routines 5.35 'acc_set_cuda_stream' - Set CUDA stream handle. ==================================================== _Description_ This function associates the stream handle specified by STREAM with the queue ASYNC. This cannot be used to change the stream handle associated with 'acc_async_sync'. The return value is not specified. _C/C++_: _Prototype_: 'int acc_set_cuda_stream(int async, void *stream);' _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section A.2.1.4.  File: libgomp.info, Node: OpenACC Environment Variables, Next: CUDA Streams Usage, Prev: OpenACC Runtime Library Routines, Up: Top 6 OpenACC Environment Variables ******************************* The variables 'ACC_DEVICE_TYPE' and 'ACC_DEVICE_NUM' are defined by section 4 of the OpenACC specification in version 2.0. The variable 'GCC_ACC_NOTIFY' is used for diagnostic purposes. * Menu: * ACC_DEVICE_TYPE:: * ACC_DEVICE_NUM:: * GCC_ACC_NOTIFY::  File: libgomp.info, Node: ACC_DEVICE_TYPE, Next: ACC_DEVICE_NUM, Up: OpenACC Environment Variables 6.1 'ACC_DEVICE_TYPE' ===================== _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 4.1.  File: libgomp.info, Node: ACC_DEVICE_NUM, Next: GCC_ACC_NOTIFY, Prev: ACC_DEVICE_TYPE, Up: OpenACC Environment Variables 6.2 'ACC_DEVICE_NUM' ==================== _Reference_: OpenACC specification v2.0 (https://www.openacc.org), section 4.2.  File: libgomp.info, Node: GCC_ACC_NOTIFY, Prev: ACC_DEVICE_NUM, Up: OpenACC Environment Variables 6.3 'GCC_ACC_NOTIFY' ==================== _Description_: Print debug information pertaining to the accelerator.  File: libgomp.info, Node: CUDA Streams Usage, Next: OpenACC Library Interoperability, Prev: OpenACC Environment Variables, Up: Top 7 CUDA Streams Usage ******************** This applies to the 'nvptx' plugin only. The library provides elements that perform asynchronous movement of data and asynchronous operation of computing constructs. This asynchronous functionality is implemented by making use of CUDA streams(1). The primary means by that the asychronous functionality is accessed is through the use of those OpenACC directives which make use of the 'async' and 'wait' clauses. When the 'async' clause is first used with a directive, it creates a CUDA stream. If an 'async-argument' is used with the 'async' clause, then the stream is associated with the specified 'async-argument'. Following the creation of an association between a CUDA stream and the 'async-argument' of an 'async' clause, both the 'wait' clause and the 'wait' directive can be used. When either the clause or directive is used after stream creation, it creates a rendezvous point whereby execution waits until all operations associated with the 'async-argument', that is, stream, have completed. Normally, the management of the streams that are created as a result of using the 'async' clause, is done without any intervention by the caller. This implies the association between the 'async-argument' and the CUDA stream will be maintained for the lifetime of the program. However, this association can be changed through the use of the library function 'acc_set_cuda_stream'. When the function 'acc_set_cuda_stream' is called, the CUDA stream that was originally associated with the 'async' clause will be destroyed. Caution should be taken when changing the association as subsequent references to the 'async-argument' refer to a different CUDA stream. ---------- Footnotes ---------- (1) See "Stream Management" in "CUDA Driver API", TRM-06703-001, Version 5.5, for additional information  File: libgomp.info, Node: OpenACC Library Interoperability, Next: The libgomp ABI, Prev: CUDA Streams Usage, Up: Top 8 OpenACC Library Interoperability ********************************** 8.1 Introduction ================ The OpenACC library uses the CUDA Driver API, and may interact with programs that use the Runtime library directly, or another library based on the Runtime library, e.g., CUBLAS(1). This chapter describes the use cases and what changes are required in order to use both the OpenACC library and the CUBLAS and Runtime libraries within a program. 8.2 First invocation: NVIDIA CUBLAS library API =============================================== In this first use case (see below), a function in the CUBLAS library is called prior to any of the functions in the OpenACC library. More specifically, the function 'cublasCreate()'. When invoked, the function initializes the library and allocates the hardware resources on the host and the device on behalf of the caller. Once the initialization and allocation has completed, a handle is returned to the caller. The OpenACC library also requires initialization and allocation of hardware resources. Since the CUBLAS library has already allocated the hardware resources for the device, all that is left to do is to initialize the OpenACC library and acquire the hardware resources on the host. Prior to calling the OpenACC function that initializes the library and allocate the host hardware resources, you need to acquire the device number that was allocated during the call to 'cublasCreate()'. The invoking of the runtime library function 'cudaGetDevice()' accomplishes this. Once acquired, the device number is passed along with the device type as parameters to the OpenACC library function 'acc_set_device_num()'. Once the call to 'acc_set_device_num()' has completed, the OpenACC library uses the context that was created during the call to 'cublasCreate()'. In other words, both libraries will be sharing the same context. /* Create the handle */ s = cublasCreate(&h); if (s != CUBLAS_STATUS_SUCCESS) { fprintf(stderr, "cublasCreate failed %d\n", s); exit(EXIT_FAILURE); } /* Get the device number */ e = cudaGetDevice(&dev); if (e != cudaSuccess) { fprintf(stderr, "cudaGetDevice failed %d\n", e); exit(EXIT_FAILURE); } /* Initialize OpenACC library and use device 'dev' */ acc_set_device_num(dev, acc_device_nvidia); Use Case 1 8.3 First invocation: OpenACC library API ========================================= In this second use case (see below), a function in the OpenACC library is called prior to any of the functions in the CUBLAS library. More specificially, the function 'acc_set_device_num()'. In the use case presented here, the function 'acc_set_device_num()' is used to both initialize the OpenACC library and allocate the hardware resources on the host and the device. In the call to the function, the call parameters specify which device to use and what device type to use, i.e., 'acc_device_nvidia'. It should be noted that this is but one method to initialize the OpenACC library and allocate the appropriate hardware resources. Other methods are available through the use of environment variables and these will be discussed in the next section. Once the call to 'acc_set_device_num()' has completed, other OpenACC functions can be called as seen with multiple calls being made to 'acc_copyin()'. In addition, calls can be made to functions in the CUBLAS library. In the use case a call to 'cublasCreate()' is made subsequent to the calls to 'acc_copyin()'. As seen in the previous use case, a call to 'cublasCreate()' initializes the CUBLAS library and allocates the hardware resources on the host and the device. However, since the device has already been allocated, 'cublasCreate()' will only initialize the CUBLAS library and allocate the appropriate hardware resources on the host. The context that was created as part of the OpenACC initialization is shared with the CUBLAS library, similarly to the first use case. dev = 0; acc_set_device_num(dev, acc_device_nvidia); /* Copy the first set to the device */ d_X = acc_copyin(&h_X[0], N * sizeof (float)); if (d_X == NULL) { fprintf(stderr, "copyin error h_X\n"); exit(EXIT_FAILURE); } /* Copy the second set to the device */ d_Y = acc_copyin(&h_Y1[0], N * sizeof (float)); if (d_Y == NULL) { fprintf(stderr, "copyin error h_Y1\n"); exit(EXIT_FAILURE); } /* Create the handle */ s = cublasCreate(&h); if (s != CUBLAS_STATUS_SUCCESS) { fprintf(stderr, "cublasCreate failed %d\n", s); exit(EXIT_FAILURE); } /* Perform saxpy using CUBLAS library function */ s = cublasSaxpy(h, N, &alpha, d_X, 1, d_Y, 1); if (s != CUBLAS_STATUS_SUCCESS) { fprintf(stderr, "cublasSaxpy failed %d\n", s); exit(EXIT_FAILURE); } /* Copy the results from the device */ acc_memcpy_from_device(&h_Y1[0], d_Y, N * sizeof (float)); Use Case 2 8.4 OpenACC library and environment variables ============================================= There are two environment variables associated with the OpenACC library that may be used to control the device type and device number: 'ACC_DEVICE_TYPE' and 'ACC_DEVICE_NUM', respecively. These two environement variables can be used as an alternative to calling 'acc_set_device_num()'. As seen in the second use case, the device type and device number were specified using 'acc_set_device_num()'. If however, the aforementioned environment variables were set, then the call to 'acc_set_device_num()' would not be required. The use of the environment variables is only relevant when an OpenACC function is called prior to a call to 'cudaCreate()'. If 'cudaCreate()' is called prior to a call to an OpenACC function, then you must call 'acc_set_device_num()'(2) ---------- Footnotes ---------- (1) See section 2.26, "Interactions with the CUDA Driver API" in "CUDA Runtime API", Version 5.5, and section 2.27, "VDPAU Interoperability", in "CUDA Driver API", TRM-06703-001, Version 5.5, for additional information on library interoperability. (2) More complete information about 'ACC_DEVICE_TYPE' and 'ACC_DEVICE_NUM' can be found in sections 4.1 and 4.2 of the OpenACC (https://www.openacc.org) Application Programming Interface”, Version 2.0.  File: libgomp.info, Node: The libgomp ABI, Next: Reporting Bugs, Prev: OpenACC Library Interoperability, Up: Top 9 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:: * Implementing OpenACC's PARALLEL construct::  File: libgomp.info, Node: Implementing MASTER construct, Next: Implementing CRITICAL construct, Up: The libgomp ABI 9.1 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 9.2 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_ __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 9.3 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 9.4 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 9.5 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 9.6 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 9.7 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 9.8 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 9.9 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 9.10 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 9.11 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 9.12 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 9.13 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, Next: Implementing OpenACC's PARALLEL construct, Prev: Implementing SECTIONS construct, Up: The libgomp ABI 9.14 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: Implementing OpenACC's PARALLEL construct, Prev: Implementing SINGLE construct, Up: The libgomp ABI 9.15 Implementing OpenACC's PARALLEL construct ============================================== void GOACC_parallel ()  File: libgomp.info, Node: Reporting Bugs, Next: Copying, Prev: The libgomp ABI, Up: Top 10 Reporting Bugs ***************** Bugs in the GNU Offloading and Multi Processing Runtime Library should be reported via Bugzilla (http://gcc.gnu.org/bugzilla/). Please add "openacc", or "openmp", or both to the keywords field in the bug report, as appropriate.  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. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. Preamble ======== The GNU General Public License is a free, copyleft license for software 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 share and change all versions of a program-to make sure it remains free software for all its users. 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This License acknowledges your rights of fair use or other equivalent, as provided by copyright law. You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you. Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary. 3. Protecting Users' Legal Rights From Anti-Circumvention Law. 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You may convey verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program. You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee. 5. Conveying Modified Source Versions. You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions: a. The work must carry prominent notices stating that you modified it, and giving a relevant date. b. 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Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange. b. Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge. c. 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Regardless of what server hosts the Corresponding Source, you remain obligated to ensure that it is available for as long as needed to satisfy these requirements. e. Convey the object code using peer-to-peer transmission, provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d. A separable portion of the object code, whose source code is excluded from the Corresponding Source as a System Library, need not be included in conveying the object code work. A "User Product" is either (1) a "consumer product", which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling. In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage. 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Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network. Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying. 7. Additional Terms. "Additional permissions" are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law. If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions. When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission. Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms: a. Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or b. 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If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying. If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms. Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way. 8. Termination. You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11). 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, you do not qualify to receive new licenses for the same material under section 10. 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 transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so. 10. Automatic Licensing of Downstream Recipients. Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License. An "entity transaction" is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts. You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it. 11. Patents. A "contributor" is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor's "contributor version". A contributor's "essential patent claims" are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, "control" includes the right to grant patent sublicenses in a manner consistent with the requirements of this License. Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version. In the following three paragraphs, a "patent license" is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To "grant" such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party. If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. "Knowingly relying" means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid. If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it. A patent license is "discriminatory" if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007. Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law. 12. No Surrender of Others' Freedom. If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program. 13. Use with the GNU Affero General Public License. Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such. 14. Revised Versions of this License. The Free Software Foundation may publish revised and/or new versions of the GNU General Public 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. Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License "or any later version" applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation. If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program. Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version. 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" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. 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 connection with the Program, unless a warranty or assumption of 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 . 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 . 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 .  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. 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 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. 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. 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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. 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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 . 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. 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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 ************* [index] * Menu: * Environment Variable: OMP_CANCELLATION. (line 6) * Environment Variable <1>: OMP_DISPLAY_ENV. (line 6) * Environment Variable <2>: OMP_DEFAULT_DEVICE. (line 6) * Environment Variable <3>: OMP_DYNAMIC. (line 6) * Environment Variable <4>: OMP_MAX_ACTIVE_LEVELS. (line 6) * Environment Variable <5>: OMP_MAX_TASK_PRIORITY. (line 6) * Environment Variable <6>: OMP_NESTED. (line 6) * Environment Variable <7>: OMP_NUM_THREADS. (line 6) * Environment Variable <8>: OMP_PROC_BIND. (line 6) * Environment Variable <9>: OMP_PLACES. (line 6) * Environment Variable <10>: OMP_STACKSIZE. (line 6) * Environment Variable <11>: OMP_SCHEDULE. (line 6) * Environment Variable <12>: OMP_THREAD_LIMIT. (line 6) * Environment Variable <13>: OMP_WAIT_POLICY. (line 6) * Environment Variable <14>: GOMP_CPU_AFFINITY. (line 6) * Environment Variable <15>: GOMP_DEBUG. (line 6) * Environment Variable <16>: GOMP_STACKSIZE. (line 6) * Environment Variable <17>: GOMP_SPINCOUNT. (line 6) * Environment Variable <18>: GOMP_RTEMS_THREAD_POOLS. (line 6) * FDL, GNU Free Documentation License: GNU Free Documentation License. (line 6) * Implementation specific setting: OMP_NESTED. (line 6) * Implementation specific setting <1>: OMP_NUM_THREADS. (line 6) * Implementation specific setting <2>: OMP_SCHEDULE. (line 6) * Implementation specific setting <3>: GOMP_STACKSIZE. (line 6) * Implementation specific setting <4>: GOMP_SPINCOUNT. (line 6) * Implementation specific setting <5>: GOMP_RTEMS_THREAD_POOLS. (line 6) * Introduction: Top. (line 6)  Tag Table: Node: Top2083 Node: Enabling OpenMP4613 Node: Runtime Library Routines5401 Node: omp_get_active_level8478 Node: omp_get_ancestor_thread_num9178 Node: omp_get_cancellation10108 Node: omp_get_default_device10922 Node: omp_get_dynamic11598 Node: omp_get_level12473 Node: omp_get_max_active_levels13093 Node: omp_get_max_task_priority13798 Node: omp_get_max_threads14418 Node: omp_get_nested15175 Node: omp_get_num_devices16089 Node: omp_get_num_procs16610 Node: omp_get_num_teams17149 Node: omp_get_num_threads17665 Node: omp_get_proc_bind18754 Node: omp_get_schedule19675 Node: omp_get_team_num20629 Node: omp_get_team_size21128 Node: omp_get_thread_limit22088 Node: omp_get_thread_num22707 Node: omp_in_parallel23578 Node: omp_in_final24227 Node: omp_is_initial_device24901 Node: omp_set_default_device25594 Node: omp_set_dynamic26385 Node: omp_set_max_active_levels27271 Node: omp_set_nested28048 Node: omp_set_num_threads28940 Node: omp_set_schedule29808 Node: omp_init_lock30889 Node: omp_set_lock31542 Node: omp_test_lock32397 Node: omp_unset_lock33373 Node: omp_destroy_lock34304 Node: omp_init_nest_lock34981 Node: omp_set_nest_lock35716 Node: omp_test_nest_lock36631 Node: omp_unset_nest_lock37658 Node: omp_destroy_nest_lock38673 Node: omp_get_wtick39424 Node: omp_get_wtime40016 Node: Environment Variables40792 Node: OMP_CANCELLATION42361 Node: OMP_DISPLAY_ENV42894 Node: OMP_DEFAULT_DEVICE43597 Node: OMP_DYNAMIC44377 Node: OMP_MAX_ACTIVE_LEVELS44973 Node: OMP_MAX_TASK_PRIORITY45623 Node: OMP_NESTED46281 Node: OMP_NUM_THREADS46886 Node: OMP_PROC_BIND47574 Node: OMP_PLACES48766 Node: OMP_STACKSIZE50943 Node: OMP_SCHEDULE51767 Node: OMP_THREAD_LIMIT52465 Node: OMP_WAIT_POLICY53065 Node: GOMP_CPU_AFFINITY53757 Node: GOMP_DEBUG55487 Node: GOMP_STACKSIZE55994 Node: GOMP_SPINCOUNT56823 Node: GOMP_RTEMS_THREAD_POOLS58027 Node: Enabling OpenACC60205 Node: OpenACC Runtime Library Routines61198 Node: acc_get_num_devices64992 Node: acc_set_device_type65718 Node: acc_get_device_type66482 Node: acc_set_device_num67197 Node: acc_get_device_num67981 Node: acc_async_test68778 Node: acc_async_test_all69770 Node: acc_wait70670 Node: acc_wait_all71532 Node: acc_wait_all_async72291 Node: acc_wait_async73043 Node: acc_init73750 Node: acc_shutdown74396 Node: acc_on_device75064 Node: acc_malloc76068 Node: acc_free76567 Node: acc_copyin76994 Node: acc_present_or_copyin78104 Node: acc_create79730 Node: acc_present_or_create80885 Node: acc_copyout82519 Node: acc_delete83542 Node: acc_update_device84517 Node: acc_update_self85629 Node: acc_map_data86733 Node: acc_unmap_data87418 Node: acc_deviceptr87939 Node: acc_hostptr88509 Node: acc_is_present89073 Node: acc_memcpy_to_device90600 Node: acc_memcpy_from_device91263 Node: acc_get_current_cuda_device91947 Node: acc_get_current_cuda_context92544 Node: acc_get_cuda_stream93144 Node: acc_set_cuda_stream93735 Node: OpenACC Environment Variables94380 Node: ACC_DEVICE_TYPE94839 Node: ACC_DEVICE_NUM95075 Node: GCC_ACC_NOTIFY95332 Node: CUDA Streams Usage95555 Ref: CUDA Streams Usage-Footnote-197455 Node: OpenACC Library Interoperability97564 Ref: OpenACC Library Interoperability-Footnote-1103920 Ref: OpenACC Library Interoperability-Footnote-2104172 Node: The libgomp ABI104380 Node: Implementing MASTER construct105236 Node: Implementing CRITICAL construct105650 Node: Implementing ATOMIC construct106389 Node: Implementing FLUSH construct106870 Node: Implementing BARRIER construct107141 Node: Implementing THREADPRIVATE construct107410 Node: Implementing PRIVATE clause108063 Node: Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses108644 Node: Implementing REDUCTION clause109968 Node: Implementing PARALLEL construct110525 Node: Implementing FOR construct111782 Node: Implementing ORDERED construct113780 Node: Implementing SECTIONS construct114086 Node: Implementing SINGLE construct114852 Node: Implementing OpenACC's PARALLEL construct115564 Node: Reporting Bugs115822 Node: Copying116184 Node: GNU Free Documentation License153731 Node: Funding178854 Node: Library Index181380  End Tag Table