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Diffstat (limited to 'libstdc++-v3/include/parallel/par_loop.h')
| -rw-r--r-- | libstdc++-v3/include/parallel/par_loop.h | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/libstdc++-v3/include/parallel/par_loop.h b/libstdc++-v3/include/parallel/par_loop.h new file mode 100644 index 000000000..b776df4b7 --- /dev/null +++ b/libstdc++-v3/include/parallel/par_loop.h @@ -0,0 +1,139 @@ +// -*- C++ -*- + +// Copyright (C) 2007, 2008, 2009 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 3, 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. + +// Under Section 7 of GPL version 3, you are granted additional +// permissions described in the GCC Runtime Library Exception, version +// 3.1, as published by the Free Software Foundation. + +// You should have received a copy of the GNU General Public License and +// a copy of the GCC Runtime Library Exception along with this program; +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +// <http://www.gnu.org/licenses/>. + +/** @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 _RAIter, + typename _Op, + typename _Fu, + typename _Red, + typename _Result> + _Op + __for_each_template_random_access_ed(_RAIter __begin, _RAIter __end, + _Op __o, _Fu& __f, _Red __r, + _Result __base, _Result& __output, + typename std::iterator_traits<_RAIter>::difference_type __bound) + { + typedef std::iterator_traits<_RAIter> _TraitsType; + typedef typename _TraitsType::difference_type _DifferenceType; + const _DifferenceType __length = __end - __begin; + _Result *__thread_results; + bool* __constructed; + + _ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType> + (__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]; + } + + _ThreadIndex __iam = omp_get_thread_num(); + + // Neutral element. + _Result* __reduct; + + _DifferenceType + __start = equally_split_point(__length, __num_threads, __iam), + __stop = equally_split_point(__length, __num_threads, __iam + 1); + + if (__start < __stop) + { + __reduct = new _Result(__f(__o, __begin + __start)); + ++__start; + __constructed[__iam] = true; + } + else + __constructed[__iam] = false; + + for (; __start < __stop; ++__start) + *__reduct = __r(*__reduct, __f(__o, __begin + __start)); + + if (__constructed[__iam]) + { + ::new(&__thread_results[__iam]) _Result(*__reduct); + delete __reduct; + } + } //parallel + + for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) + if (__constructed[__i]) + { + __output = __r(__output, __thread_results[__i]); + __thread_results[__i].~_Result(); + } + + // Points to last element processed (needed as return value for + // some algorithms like transform). + __f._M_finish_iterator = __begin + __length; + + ::operator delete(__thread_results); + + delete[] __constructed; + + return __o; + } + +} // end namespace + +#endif /* _GLIBCXX_PARALLEL_PAR_LOOP_H */ |