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/par_loop.h 26 * @brief Parallelization of embarrassingly parallel execution by 27 * means of equal splitting. 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_PAR_LOOP_H 34 #define _GLIBCXX_PARALLEL_PAR_LOOP_H 1 35 36 #include <omp.h> 37 #include <parallel/settings.h> 38 #include <parallel/base.h> 39 #include <parallel/equally_split.h> 40 41 namespace __gnu_parallel 42 { 43 /** @brief Embarrassingly parallel algorithm for random access 44 * iterators, using hand-crafted parallelization by equal splitting 45 * the work. 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, ...) 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 _RAIter, 62 typename _Op, 63 typename _Fu, 64 typename _Red, 65 typename _Result> 66 _Op 67 __for_each_template_random_access_ed(_RAIter __begin, _RAIter __end, 68 _Op __o, _Fu& __f, _Red __r, 69 _Result __base, _Result& __output, 70 typename std::iterator_traits<_RAIter>::difference_type __bound) 71 { 72 typedef std::iterator_traits<_RAIter> _TraitsType; 73 typedef typename _TraitsType::difference_type _DifferenceType; 74 const _DifferenceType __length = __end - __begin; 75 _Result *__thread_results; 76 bool* __constructed; 77 78 _ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType> 79 (__get_max_threads(), __length); 80 81 # pragma omp parallel num_threads(__num_threads) 82 { 83 # pragma omp single 84 { 85 __num_threads = omp_get_num_threads(); 86 __thread_results = static_cast<_Result*> 87 (::operator new(__num_threads * sizeof(_Result))); 88 __constructed = new bool[__num_threads]; 89 } 90 91 _ThreadIndex __iam = omp_get_thread_num(); 92 93 // Neutral element. 94 _Result* __reduct = static_cast<_Result*> 95 (::operator new(sizeof(_Result))); 96 97 _DifferenceType 98 __start = equally_split_point(__length, __num_threads, __iam), 99 __stop = equally_split_point(__length, __num_threads, __iam + 1); 100 101 if (__start < __stop) 102 { 103 new(__reduct) _Result(__f(__o, __begin + __start)); 104 ++__start; 105 __constructed[__iam] = true; 106 } 107 else 108 __constructed[__iam] = false; 109 110 for (; __start < __stop; ++__start) 111 *__reduct = __r(*__reduct, __f(__o, __begin + __start)); 112 113 __thread_results[__iam] = *__reduct; 114 } //parallel 115 116 for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) 117 if (__constructed[__i]) 118 __output = __r(__output, __thread_results[__i]); 119 120 // Points to last element processed (needed as return value for 121 // some algorithms like transform). 122 __f._M_finish_iterator = __begin + __length; 123 124 delete[] __thread_results; 125 delete[] __constructed; 126 127 return __o; 128 } 129 130 } // end namespace 131 132 #endif /* _GLIBCXX_PARALLEL_PAR_LOOP_H */ 133