119 lines
3.9 KiB
C++
119 lines
3.9 KiB
C++
// -*- C++ -*-
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// Copyright (C) 2007, 2008, 2009 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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// 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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// 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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/** @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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// Written by Felix Putze.
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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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#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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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 "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 "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 RandomAccessIterator,
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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(RandomAccessIterator begin,
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RandomAccessIterator end,
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Op o, Fu& f, Red r, Result base,
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Result& output,
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typename std::iterator_traits
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<RandomAccessIterator>::
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difference_type bound)
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{
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typedef typename
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std::iterator_traits<RandomAccessIterator>::difference_type
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difference_type;
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difference_type length = end - begin;
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thread_index_t num_threads =
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__gnu_parallel::min<difference_type>(get_max_threads(), length);
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Result *thread_results;
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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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for (thread_index_t i = 0; i < num_threads; ++i)
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thread_results[i] = Result();
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}
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thread_index_t iam = omp_get_thread_num();
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# pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size)
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for (difference_type pos = 0; pos < length; ++pos)
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thread_results[iam] =
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r(thread_results[iam], f(o, begin+pos));
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} //parallel
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for (thread_index_t 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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// Points to last element processed (needed as return value for
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// some algorithms like transform).
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f.finish_iterator = begin + length;
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return o;
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}
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} // end namespace
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#endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */
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