112 lines
4.1 KiB
C
112 lines
4.1 KiB
C
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// -*- C++ -*-
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// Copyright (C) 2007 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 2, 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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// You should have received a copy of the GNU General Public License
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// along with this library; see the file COPYING. If not, write to
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// the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
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// MA 02111-1307, USA.
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// As a special exception, you may use this file as part of a free
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// software library without restriction. Specifically, if other files
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// instantiate templates or use macros or inline functions from this
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// file, or you compile this file and link it with other files to
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// produce an executable, this file does not by itself cause the
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// resulting executable to be covered by the GNU General Public
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// License. This exception does not however invalidate any other
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// reasons why the executable file might be covered by the GNU General
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// Public License.
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/** @file parallel/omp_loop_static.h
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* @brief Parallelization of embarrassingly parallel execution by
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* means of an OpenMP for loop with static scheduling.
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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_STATIC_H
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#define _GLIBCXX_PARALLEL_OMP_LOOP_STATIC_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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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 with static scheduling.
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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, ...).
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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 processed
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* 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, typename Op, typename Fu, typename Red, typename Result>
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Op
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for_each_template_random_access_omp_loop_static(RandomAccessIterator begin,
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RandomAccessIterator end,
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Op o, Fu& f, Red r,
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Result base, Result& output,
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typename std::iterator_traits<RandomAccessIterator>::difference_type bound)
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{
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typedef std::iterator_traits<RandomAccessIterator> traits_type;
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typedef typename traits_type::difference_type difference_type;
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thread_index_t num_threads = (get_max_threads() < (end - begin)) ? get_max_threads() : (end - begin);
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Result *thread_results = new Result[num_threads];
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difference_type length = end - begin;
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for (thread_index_t i = 0; i < num_threads; i++)
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{
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thread_results[i] = r(thread_results[i], f(o, begin+i));
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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 for schedule(static, Settings::workstealing_chunk_size)
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for (difference_type pos = 0; pos < length; pos++)
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{
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thread_results[omp_get_thread_num()] = r(thread_results[omp_get_thread_num()], f(o, begin+pos));
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}
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}
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for (thread_index_t i = 0; i < num_threads; i++)
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{
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output = r(output, thread_results[i]);
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}
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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
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