140 lines
4.4 KiB
C++
140 lines
4.4 KiB
C++
// -*- C++ -*-
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// Copyright (C) 2007-2018 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/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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#include <parallel/base.h>
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#include <parallel/equally_split.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 _RAIter,
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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_ed(_RAIter __begin, _RAIter __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<_RAIter>::difference_type __bound)
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{
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typedef std::iterator_traits<_RAIter> _TraitsType;
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typedef typename _TraitsType::difference_type _DifferenceType;
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const _DifferenceType __length = __end - __begin;
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_Result *__thread_results;
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bool* __constructed;
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_ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType>
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(__get_max_threads(), __length);
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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 = static_cast<_Result*>
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(::operator new(__num_threads * sizeof(_Result)));
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__constructed = new bool[__num_threads];
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}
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_ThreadIndex __iam = omp_get_thread_num();
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// Neutral element.
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_Result* __reduct;
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_DifferenceType
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__start = __equally_split_point(__length, __num_threads, __iam),
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__stop = __equally_split_point(__length, __num_threads, __iam + 1);
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if (__start < __stop)
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{
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__reduct = new _Result(__f(__o, __begin + __start));
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++__start;
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__constructed[__iam] = true;
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}
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else
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__constructed[__iam] = false;
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for (; __start < __stop; ++__start)
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*__reduct = __r(*__reduct, __f(__o, __begin + __start));
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if (__constructed[__iam])
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{
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::new(&__thread_results[__iam]) _Result(*__reduct);
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delete __reduct;
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}
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} //parallel
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for (_ThreadIndex __i = 0; __i < __num_threads; ++__i)
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if (__constructed[__i])
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{
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__output = __r(__output, __thread_results[__i]);
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__thread_results[__i].~_Result();
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}
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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._M_finish_iterator = __begin + __length;
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::operator delete(__thread_results);
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delete[] __constructed;
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return __o;
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}
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} // end namespace
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#endif /* _GLIBCXX_PARALLEL_PAR_LOOP_H */
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