// -*- C++ -*- // Copyright (C) 2007-2013 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 __off Returned __offsets. */ template<typename _RAIter, typename _DifferenceTp> void __calc_borders(_RAIter __elements, _DifferenceTp __length, _DifferenceTp* __off) { typedef _DifferenceTp _DifferenceType; __off[0] = -1; if (__length > 1) __off[1] = 0; _DifferenceType __k = 0; for (_DifferenceType __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 __RAIter1, typename __RAIter2, typename _Pred> __RAIter1 __search_template(__RAIter1 __begin1, __RAIter1 __end1, __RAIter2 __begin2, __RAIter2 __end2, _Pred __pred) { typedef std::iterator_traits<__RAIter1> _TraitsType; typedef typename _TraitsType::difference_type _DifferenceType; _GLIBCXX_CALL((__end1 - __begin1) + (__end2 - __begin2)); _DifferenceType __pattern_length = __end2 - __begin2; // Pattern too short. if(__pattern_length <= 0) return __end1; // Last point to start search. _DifferenceType __input_length = (__end1 - __begin1) - __pattern_length; // Where is first occurrence of pattern? defaults to end. _DifferenceType __result = (__end1 - __begin1); _DifferenceType *__splitters; // Pattern too long. if (__input_length < 0) return __end1; omp_lock_t __result_lock; omp_init_lock(&__result_lock); _ThreadIndex __num_threads = std::max<_DifferenceType> (1, std::min<_DifferenceType>(__input_length, __get_max_threads())); _DifferenceType __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 _DifferenceType[__num_threads + 1]; __equally_split(__input_length, __num_threads, __splitters); } _ThreadIndex __iam = omp_get_thread_num(); _DifferenceType __start = __splitters[__iam], __stop = __splitters[__iam + 1]; _DifferenceType __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 */