source: Daodan/MSYS2/mingw32/include/c++/11.2.0/parallel/omp_loop.h@ 1171

Last change on this file since 1171 was 1166, checked in by rossy, 3 years ago

Daodan: Replace MinGW build env with an up-to-date MSYS2 env

File size: 3.9 KB
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[1166]1// -*- C++ -*-
2
3// Copyright (C) 2007-2021 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the terms
7// of the GNU General Public License as published by the Free Software
8// Foundation; either version 3, or (at your option) any later
9// version.
10
11// This library is distributed in the hope that it will be useful, but
12// WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14// General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file parallel/omp_loop.h
26 * @brief Parallelization of embarrassingly parallel execution by
27 * means of an OpenMP for loop.
28 * This file is a GNU parallel extension to the Standard C++ Library.
29 */
30
31// Written by Felix Putze.
32
33#ifndef _GLIBCXX_PARALLEL_OMP_LOOP_H
34#define _GLIBCXX_PARALLEL_OMP_LOOP_H 1
35
36#include <omp.h>
37
38#include <parallel/settings.h>
39#include <parallel/basic_iterator.h>
40#include <parallel/base.h>
41
42namespace __gnu_parallel
43{
44 /** @brief Embarrassingly parallel algorithm for random access
45 * iterators, using an OpenMP for loop.
46 *
47 * @param __begin Begin iterator of element sequence.
48 * @param __end End iterator of element sequence.
49 * @param __o User-supplied functor (comparator, predicate, adding
50 * functor, etc.).
51 * @param __f Functor to @a process an element with __op (depends on
52 * desired functionality, e. g. for std::for_each(), ...).
53 * @param __r Functor to @a add a single __result to the already
54 * processed elements (depends on functionality).
55 * @param __base Base value for reduction.
56 * @param __output Pointer to position where final result is written to
57 * @param __bound Maximum number of elements processed (e. g. for
58 * std::count_n()).
59 * @return User-supplied functor (that may contain a part of the result).
60 */
61 template<typename _RAIter,
62 typename _Op,
63 typename _Fu,
64 typename _Red,
65 typename _Result>
66 _Op
67 __for_each_template_random_access_omp_loop(_RAIter __begin, _RAIter __end,
68 _Op __o, _Fu& __f, _Red __r,
69 _Result __base,
70 _Result& __output,
71 typename std::iterator_traits<_RAIter>::difference_type __bound)
72 {
73 typedef typename std::iterator_traits<_RAIter>::difference_type
74 _DifferenceType;
75
76 _DifferenceType __length = __end - __begin;
77 _ThreadIndex __num_threads = __gnu_parallel::min<_DifferenceType>
78 (__get_max_threads(), __length);
79
80 _Result *__thread_results;
81
82# pragma omp parallel num_threads(__num_threads)
83 {
84# pragma omp single
85 {
86 __num_threads = omp_get_num_threads();
87 __thread_results = new _Result[__num_threads];
88
89 for (_ThreadIndex __i = 0; __i < __num_threads; ++__i)
90 __thread_results[__i] = _Result();
91 }
92
93 _ThreadIndex __iam = omp_get_thread_num();
94
95#pragma omp for schedule(dynamic, _Settings::get().workstealing_chunk_size)
96 for (_DifferenceType __pos = 0; __pos < __length; ++__pos)
97 __thread_results[__iam] = __r(__thread_results[__iam],
98 __f(__o, __begin+__pos));
99 } //parallel
100
101 for (_ThreadIndex __i = 0; __i < __num_threads; ++__i)
102 __output = __r(__output, __thread_results[__i]);
103
104 delete [] __thread_results;
105
106 // Points to last element processed (needed as return value for
107 // some algorithms like transform).
108 __f._M_finish_iterator = __begin + __length;
109
110 return __o;
111 }
112
113} // end namespace
114
115#endif /* _GLIBCXX_PARALLEL_OMP_LOOP_H */
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