3 // Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
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
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.
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.
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/>.
25 /** @file parallel/omp_loop_static.h
26 * @brief Parallelization of embarrassingly parallel execution by
27 * means of an OpenMP for loop with static scheduling.
28 * This file is a GNU parallel extension to the Standard C++ Library.
31 // Written by Felix Putze.
33 #ifndef _GLIBCXX_PARALLEL_OMP_LOOP_STATIC_H
34 #define _GLIBCXX_PARALLEL_OMP_LOOP_STATIC_H 1
38 #include <parallel/settings.h>
39 #include <parallel/basic_iterator.h>
41 namespace __gnu_parallel
44 /** @brief Embarrassingly parallel algorithm for random access
45 * iterators, using an OpenMP for loop with static scheduling.
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
51 * @param f Functor to "process" an element with op (depends on
52 * desired functionality, e. g. for std::for_each(), ...).
53 * @param r Functor to "add" a single result to the already processed
54 * 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
59 * @return User-supplied functor (that may contain a part of the result).
61 template<typename RandomAccessIterator,
67 for_each_template_random_access_omp_loop_static(RandomAccessIterator begin,
68 RandomAccessIterator end,
70 Result base, Result& output,
71 typename std::iterator_traits
72 <RandomAccessIterator>::
73 difference_type bound)
76 std::iterator_traits<RandomAccessIterator>::difference_type
79 difference_type length = end - begin;
80 thread_index_t num_threads =
81 std::min<difference_type>(get_max_threads(), length);
83 Result *thread_results;
85 # pragma omp parallel num_threads(num_threads)
89 num_threads = omp_get_num_threads();
90 thread_results = new Result[num_threads];
92 for (thread_index_t i = 0; i < num_threads; ++i)
93 thread_results[i] = Result();
96 thread_index_t iam = omp_get_thread_num();
98 # pragma omp for schedule(static, _Settings::get().workstealing_chunk_size)
99 for (difference_type pos = 0; pos < length; ++pos)
100 thread_results[iam] = r(thread_results[iam], f(o, begin+pos));
103 for (thread_index_t i = 0; i < num_threads; ++i)
104 output = r(output, thread_results[i]);
106 delete [] thread_results;
108 // Points to last element processed (needed as return value for
109 // some algorithms like transform).
110 f.finish_iterator = begin + length;
117 #endif /* _GLIBCXX_PARALLEL_OMP_LOOP_STATIC_H */