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Diffstat (limited to 'gcc-4.4.3/libstdc++-v3/include/parallel/search.h')
| -rw-r--r-- | gcc-4.4.3/libstdc++-v3/include/parallel/search.h | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/gcc-4.4.3/libstdc++-v3/include/parallel/search.h b/gcc-4.4.3/libstdc++-v3/include/parallel/search.h new file mode 100644 index 000000000..31a853402 --- /dev/null +++ b/gcc-4.4.3/libstdc++-v3/include/parallel/search.h @@ -0,0 +1,172 @@ +// -*- 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/search.h + * @brief Parallel implementation base for std::search() and + * std::search_n(). + * This file is a GNU parallel extension to the Standard C++ Library. + */ + +// Written by Felix Putze. + +#ifndef _GLIBCXX_PARALLEL_SEARCH_H +#define _GLIBCXX_PARALLEL_SEARCH_H 1 + +#include <bits/stl_algobase.h> + +#include <parallel/parallel.h> +#include <parallel/equally_split.h> + + +namespace __gnu_parallel +{ + /** + * @brief Precalculate advances for Knuth-Morris-Pratt algorithm. + * @param elements Begin iterator of sequence to search for. + * @param length Length of sequence to search for. + * @param advances Returned offsets. + */ +template<typename RandomAccessIterator, typename _DifferenceTp> + void + calc_borders(RandomAccessIterator elements, _DifferenceTp length, + _DifferenceTp* off) + { + typedef _DifferenceTp difference_type; + + off[0] = -1; + if (length > 1) + off[1] = 0; + difference_type k = 0; + for (difference_type j = 2; j <= length; j++) + { + while ((k >= 0) && !(elements[k] == elements[j-1])) + k = off[k]; + off[j] = ++k; + } + } + + // Generic parallel find algorithm (requires random access iterator). + + /** @brief Parallel std::search. + * @param begin1 Begin iterator of first sequence. + * @param end1 End iterator of first sequence. + * @param begin2 Begin iterator of second sequence. + * @param end2 End iterator of second sequence. + * @param pred Find predicate. + * @return Place of finding in first sequences. */ +template<typename _RandomAccessIterator1, + typename _RandomAccessIterator2, + typename Pred> + _RandomAccessIterator1 + search_template(_RandomAccessIterator1 begin1, _RandomAccessIterator1 end1, + _RandomAccessIterator2 begin2, _RandomAccessIterator2 end2, + Pred pred) + { + typedef std::iterator_traits<_RandomAccessIterator1> traits_type; + typedef typename traits_type::difference_type difference_type; + + _GLIBCXX_CALL((end1 - begin1) + (end2 - begin2)); + + difference_type pattern_length = end2 - begin2; + + // Pattern too short. + if(pattern_length <= 0) + return end1; + + // Last point to start search. + difference_type input_length = (end1 - begin1) - pattern_length; + + // Where is first occurrence of pattern? defaults to end. + difference_type result = (end1 - begin1); + difference_type *splitters; + + // Pattern too long. + if (input_length < 0) + return end1; + + omp_lock_t result_lock; + omp_init_lock(&result_lock); + + thread_index_t num_threads = + std::max<difference_type>(1, + std::min<difference_type>(input_length, get_max_threads())); + + difference_type advances[pattern_length]; + calc_borders(begin2, pattern_length, advances); + +# pragma omp parallel num_threads(num_threads) + { +# pragma omp single + { + num_threads = omp_get_num_threads(); + splitters = new difference_type[num_threads + 1]; + equally_split(input_length, num_threads, splitters); + } + + thread_index_t iam = omp_get_thread_num(); + + difference_type start = splitters[iam], stop = splitters[iam + 1]; + + difference_type pos_in_pattern = 0; + bool found_pattern = false; + + while (start <= stop && !found_pattern) + { + // Get new value of result. + #pragma omp flush(result) + // No chance for this thread to find first occurrence. + if (result < start) + break; + while (pred(begin1[start + pos_in_pattern], + begin2[pos_in_pattern])) + { + ++pos_in_pattern; + if (pos_in_pattern == pattern_length) + { + // Found new candidate for result. + omp_set_lock(&result_lock); + result = std::min(result, start); + omp_unset_lock(&result_lock); + + found_pattern = true; + break; + } + } + // Make safe jump. + start += (pos_in_pattern - advances[pos_in_pattern]); + pos_in_pattern = + (advances[pos_in_pattern] < 0) ? 0 : advances[pos_in_pattern]; + } + } //parallel + + omp_destroy_lock(&result_lock); + + delete[] splitters; + + // Return iterator on found element. + return (begin1 + result); + } +} // end namespace + +#endif /* _GLIBCXX_PARALLEL_SEARCH_H */ |