// -*- C++ -*- // Copyright (C) 2007-2018 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 // . /** @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 #include #include #include 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 _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 */