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// -*- C++ -*- |
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// Copyright (C) 2007-2021 Free Software Foundation, Inc. |
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// |
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// This file is part of the GNU ISO C++ Library. This library is free |
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// software; you can redistribute it and/or modify it under the terms |
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// of the GNU General Public License as published by the Free Software |
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// Foundation; either version 3, or (at your option) any later |
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// version. |
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// This library is distributed in the hope that it will be useful, but |
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// WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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// General Public License for more details. |
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|
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// Under Section 7 of GPL version 3, you are granted additional |
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// permissions described in the GCC Runtime Library Exception, version |
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// 3.1, as published by the Free Software Foundation. |
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|
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// You should have received a copy of the GNU General Public License and |
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// a copy of the GCC Runtime Library Exception along with this program; |
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
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// <http://www.gnu.org/licenses/>. |
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|
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/** @file parallel/omp_loop.h |
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* @brief Parallelization of embarrassingly parallel execution by |
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* means of an OpenMP for loop. |
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* This file is a GNU parallel extension to the Standard C++ Library. |
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*/ |
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|
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// Written by Felix Putze. |
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|
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#ifndef _GLIBCXX_PARALLEL_OMP_LOOP_H |
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#define _GLIBCXX_PARALLEL_OMP_LOOP_H 1 |
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#include <omp.h> |
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|
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#include <parallel/settings.h> |
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#include <parallel/basic_iterator.h> |
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#include <parallel/base.h> |
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|
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namespace __gnu_parallel |
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{ |
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/** @brief Embarrassingly parallel algorithm for random access |
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* iterators, using an OpenMP for loop. |
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* |
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* @param __begin Begin iterator of element sequence. |
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* @param __end End iterator of element sequence. |
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* @param __o User-supplied functor (comparator, predicate, adding |
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* functor, etc.). |
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* @param __f Functor to @a process an element with __op (depends on |
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* desired functionality, e. g. for std::for_each(), ...). |
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* @param __r Functor to @a add a single __result to the already |
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* processed elements (depends on functionality). |
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* @param __base Base value for reduction. |
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* @param __output Pointer to position where final result is written to |
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* @param __bound Maximum number of elements processed (e. g. for |
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* std::count_n()). |
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* @return User-supplied functor (that may contain a part of the result). |
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*/ |
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template<typename _RAIter, |
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typename _Op, |
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typename _Fu, |
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typename _Red, |
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typename _Result> |
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_Op |
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__for_each_template_random_access_omp_loop(_RAIter __begin, _RAIter __end, |
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_Op __o, _Fu& __f, _Red __r, |
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_Result __base, |
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_Result& __output, |
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typename std::iterator_traits<_RAIter>::difference_type __bound) |
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{ |
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typedef typename std::iterator_traits<_RAIter>::difference_type |
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_DifferenceType; |
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|
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_DifferenceType __length = __end - __begin; |
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_ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType> |
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(__get_max_threads(), __length); |
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|
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_Result *__thread_results; |
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|
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# pragma omp parallel num_threads(__num_threads) |
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{ |
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# pragma omp single |
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{ |
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__num_threads = omp_get_num_threads(); |
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__thread_results = new _Result[__num_threads]; |
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|
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for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) |
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__thread_results[__i] = _Result(); |
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} |
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|
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_ThreadIndex __iam = omp_get_thread_num(); |
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|
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#pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size) |
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for (_DifferenceType __pos = 0; __pos < __length; ++__pos) |
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__thread_results[__iam] = __r(__thread_results[__iam], |
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__f(__o, __begin+__pos)); |
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} //parallel |
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|
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for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) |
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__output = __r(__output, __thread_results[__i]); |
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delete [] __thread_results; |
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|
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// Points to last element processed (needed as return value for |
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// some algorithms like transform). |
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__f._M_finish_iterator = __begin + __length; |
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|
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return __o; |
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} |
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|
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} // end namespace |
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|
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#endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */ |
