1 // -*- C++ -*- 2 3 // Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the terms 7 // of the GNU General Public License as published by the Free Software 8 // Foundation; either version 3, or (at your option) any later 9 // version. 10 11 // This library is distributed in the hope that it will be useful, but 12 // WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 // General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /** @file parallel/omp_loop.h 26 * @brief Parallelization of embarrassingly parallel execution by 27 * means of an OpenMP for loop. 28 * This file is a GNU parallel extension to the Standard C++ Library. 29 */ 30 31 // Written by Felix Putze. 32 33 #ifndef _GLIBCXX_PARALLEL_OMP_LOOP_H 34 #define _GLIBCXX_PARALLEL_OMP_LOOP_H 1 35 36 #include <omp.h> 37 38 #include <parallel/settings.h> 39 #include <parallel/basic_iterator.h> 40 #include <parallel/base.h> 41 42 namespace __gnu_parallel 43 { 44 /** @brief Embarrassingly parallel algorithm for random access 45 * iterators, using an OpenMP for loop. 46 * 47 * @param begin Begin iterator of element sequence. 48 * @param end End iterator of element sequence. 49 * @param o User-supplied functor (comparator, predicate, adding 50 * functor, etc.). 51 * @param f Functor to "process" an element with op (depends on 52 * desired functionality, e. g. for std::for_each(), ...). 53 * @param r Functor to "add" a single result to the already 54 * processed elements (depends on functionality). 55 * @param base Base value for reduction. 56 * @param output Pointer to position where final result is written to 57 * @param bound Maximum number of elements processed (e. g. for 58 * std::count_n()). 59 * @return User-supplied functor (that may contain a part of the result). 60 */ 61 template<typename RandomAccessIterator, 62 typename Op, 63 typename Fu, 64 typename Red, 65 typename Result> 66 Op 67 for_each_template_random_access_omp_loop(RandomAccessIterator begin, 68 RandomAccessIterator end, 69 Op o, Fu& f, Red r, Result base, 70 Result& output, 71 typename std::iterator_traits 72 <RandomAccessIterator>:: 73 difference_type bound) 74 { 75 typedef typename 76 std::iterator_traits<RandomAccessIterator>::difference_type 77 difference_type; 78 79 difference_type length = end - begin; 80 thread_index_t num_threads = 81 __gnu_parallel::min<difference_type>(get_max_threads(), length); 82 83 Result *thread_results; 84 85 # pragma omp parallel num_threads(num_threads) 86 { 87 # pragma omp single 88 { 89 num_threads = omp_get_num_threads(); 90 thread_results = new Result[num_threads]; 91 92 for (thread_index_t i = 0; i < num_threads; ++i) 93 thread_results[i] = Result(); 94 } 95 96 thread_index_t iam = omp_get_thread_num(); 97 98 # pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size) 99 for (difference_type pos = 0; pos < length; ++pos) 100 thread_results[iam] = 101 r(thread_results[iam], f(o, begin+pos)); 102 } //parallel 103 104 for (thread_index_t i = 0; i < num_threads; ++i) 105 output = r(output, thread_results[i]); 106 107 delete [] thread_results; 108 109 // Points to last element processed (needed as return value for 110 // some algorithms like transform). 111 f.finish_iterator = begin + length; 112 113 return o; 114 } 115 116 } // end namespace 117 118 #endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */ 119
