| // -*- C++ -*- |
| |
| // Copyright (C) 2007-2020 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library 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, or (at your option) any later |
| // version. |
| |
| // This library 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. |
| |
| // Under Section 7 of GPL version 3, you are granted additional |
| // permissions described in the GCC Runtime Library Exception, version |
| // 3.1, as published by the Free Software Foundation. |
| |
| // You should have received a copy of the GNU General Public License and |
| // a copy of the GCC Runtime Library Exception along with this program; |
| // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| // <http://www.gnu.org/licenses/>. |
| |
| /** @file parallel/omp_loop.h |
| * @brief Parallelization of embarrassingly parallel execution by |
| * means of an OpenMP for loop. |
| * This file is a GNU parallel extension to the Standard C++ Library. |
| */ |
| |
| // Written by Felix Putze. |
| |
| #ifndef _GLIBCXX_PARALLEL_OMP_LOOP_H |
| #define _GLIBCXX_PARALLEL_OMP_LOOP_H 1 |
| |
| #include <omp.h> |
| |
| #include <parallel/settings.h> |
| #include <parallel/basic_iterator.h> |
| #include <parallel/base.h> |
| |
| namespace __gnu_parallel |
| { |
| /** @brief Embarrassingly parallel algorithm for random access |
| * iterators, using an OpenMP for loop. |
| * |
| * @param __begin Begin iterator of element sequence. |
| * @param __end End iterator of element sequence. |
| * @param __o User-supplied functor (comparator, predicate, adding |
| * functor, etc.). |
| * @param __f Functor to @a process an element with __op (depends on |
| * desired functionality, e. g. for std::for_each(), ...). |
| * @param __r Functor to @a add a single __result to the already |
| * processed elements (depends on functionality). |
| * @param __base Base value for reduction. |
| * @param __output Pointer to position where final result is written to |
| * @param __bound Maximum number of elements processed (e. g. for |
| * std::count_n()). |
| * @return User-supplied functor (that may contain a part of the result). |
| */ |
| template<typename _RAIter, |
| typename _Op, |
| typename _Fu, |
| typename _Red, |
| typename _Result> |
| _Op |
| __for_each_template_random_access_omp_loop(_RAIter __begin, _RAIter __end, |
| _Op __o, _Fu& __f, _Red __r, |
| _Result __base, |
| _Result& __output, |
| typename std::iterator_traits<_RAIter>::difference_type __bound) |
| { |
| typedef typename std::iterator_traits<_RAIter>::difference_type |
| _DifferenceType; |
| |
| _DifferenceType __length = __end - __begin; |
| _ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType> |
| (__get_max_threads(), __length); |
| |
| _Result *__thread_results; |
| |
| # pragma omp parallel num_threads(__num_threads) |
| { |
| # pragma omp single |
| { |
| __num_threads = omp_get_num_threads(); |
| __thread_results = new _Result[__num_threads]; |
| |
| for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) |
| __thread_results[__i] = _Result(); |
| } |
| |
| _ThreadIndex __iam = omp_get_thread_num(); |
| |
| #pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size) |
| for (_DifferenceType __pos = 0; __pos < __length; ++__pos) |
| __thread_results[__iam] = __r(__thread_results[__iam], |
| __f(__o, __begin+__pos)); |
| } //parallel |
| |
| for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) |
| __output = __r(__output, __thread_results[__i]); |
| |
| delete [] __thread_results; |
| |
| // Points to last element processed (needed as return value for |
| // some algorithms like transform). |
| __f._M_finish_iterator = __begin + __length; |
| |
| return __o; |
| } |
| |
| } // end namespace |
| |
| #endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */ |