// -*- C++ -*- // Copyright (C) 2007, 2008 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the terms // of the GNU General Public License as published by the Free Software // Foundation; either version 2, or (at your option) any later // version. // This library is distributed in the hope that it will be useful, but // WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU // General Public License for more details. // You should have received a copy of the GNU General Public License // along with this library; see the file COPYING. If not, write to // the Free Software Foundation, 59 Temple Place - Suite 330, Boston, // MA 02111-1307, USA. // As a special exception, you may use this file as part of a free // software library without restriction. Specifically, if other files // instantiate templates or use macros or inline functions from this // file, or you compile this file and link it with other files to // produce an executable, this file does not by itself cause the // resulting executable to be covered by the GNU General Public // License. This exception does not however invalidate any other // reasons why the executable file might be covered by the GNU General // Public License. /** @file parallel/par_loop.h * @brief Parallelization of embarrassingly parallel execution by * means of equal splitting. * This file is a GNU parallel extension to the Standard C++ Library. */ // Written by Felix Putze. #ifndef _GLIBCXX_PARALLEL_PAR_LOOP_H #define _GLIBCXX_PARALLEL_PAR_LOOP_H 1 #include <omp.h> #include <parallel/settings.h> #include <parallel/base.h> #include <parallel/equally_split.h> namespace __gnu_parallel { /** @brief Embarrassingly parallel algorithm for random access * iterators, using hand-crafted parallelization by equal splitting * the work. * * @param begin Begin iterator of element sequence. * @param end End iterator of element sequence. * @param o User-supplied functor (comparator, predicate, adding * functor, ...) * @param f Functor to "process" an element with op (depends on * desired functionality, e. g. for std::for_each(), ...). * @param r Functor to "add" a single result to the already * processed elements (depends on functionality). * @param base Base value for reduction. * @param output Pointer to position where final result is written to * @param bound Maximum number of elements processed (e. g. for * std::count_n()). * @return User-supplied functor (that may contain a part of the result). */ template<typename RandomAccessIterator, typename Op, typename Fu, typename Red, typename Result> Op for_each_template_random_access_ed(RandomAccessIterator begin, RandomAccessIterator end, Op o, Fu& f, Red r, Result base, Result& output, typename std::iterator_traits <RandomAccessIterator>:: difference_type bound) { typedef std::iterator_traits<RandomAccessIterator> traits_type; typedef typename traits_type::difference_type difference_type; const difference_type length = end - begin; Result *thread_results; bool* constructed; thread_index_t num_threads = __gnu_parallel::min<difference_type>(get_max_threads(), length); # pragma omp parallel num_threads(num_threads) { # pragma omp single { num_threads = omp_get_num_threads(); thread_results = static_cast<Result*>( ::operator new(num_threads * sizeof(Result))); constructed = new bool[num_threads]; } thread_index_t iam = omp_get_thread_num(); // Neutral element. Result* reduct = static_cast<Result*>(::operator new(sizeof(Result))); difference_type start = equally_split_point(length, num_threads, iam), stop = equally_split_point(length, num_threads, iam + 1); if (start < stop) { new(reduct) Result(f(o, begin + start)); ++start; constructed[iam] = true; } else constructed[iam] = false; for (; start < stop; ++start) *reduct = r(*reduct, f(o, begin + start)); thread_results[iam] = *reduct; } //parallel for (thread_index_t i = 0; i < num_threads; ++i) if (constructed[i]) output = r(output, thread_results[i]); // Points to last element processed (needed as return value for // some algorithms like transform). f.finish_iterator = begin + length; delete[] thread_results; delete[] constructed; return o; } } // end namespace #endif /* _GLIBCXX_PARALLEL_PAR_LOOP_H */