mirror of git://gcc.gnu.org/git/gcc.git
121 lines
4.3 KiB
C++
121 lines
4.3 KiB
C++
// -*- 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/par_loop.h
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* @brief Parallelization of embarrassingly parallel execution by
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* means of equal splitting.
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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_PAR_LOOP_H
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#define _GLIBCXX_PARALLEL_PAR_LOOP_H 1
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#include <omp.h>
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#include <parallel/settings.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 hand-crafted parallelization by equal splitting
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* the work.
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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
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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, typename Op, typename Fu, typename Red, typename Result>
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Op
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for_each_template_random_access_ed(RandomAccessIterator begin,
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RandomAccessIterator end, Op o, Fu& f,
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Red r, 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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const difference_type length = end - begin;
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const difference_type settings_threads = static_cast<difference_type>(get_max_threads());
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const difference_type dmin = settings_threads < length ? settings_threads : length;
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const difference_type dmax = dmin > 1 ? dmin : 1;
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thread_index_t num_threads = static_cast<thread_index_t>(dmax);
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Result *thread_results = new Result[num_threads];
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#pragma omp parallel num_threads(num_threads)
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{
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// Neutral element.
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Result reduct = Result();
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thread_index_t p = num_threads;
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thread_index_t iam = omp_get_thread_num();
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difference_type start = iam * length / p;
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difference_type limit = (iam == p - 1) ? length : (iam + 1) * length / p;
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if (start < limit)
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{
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reduct = f(o, begin + start);
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start++;
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}
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for (; start < limit; start++)
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reduct = r(reduct, f(o, begin + start));
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thread_results[iam] = reduct;
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}
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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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// 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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