// -*- C++ -*- // Copyright (C) 2007-2020 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/find.h * @brief Parallel implementation base for std::find(), std::equal() * and related functions. * This file is a GNU parallel extension to the Standard C++ Library. */ // Written by Felix Putze and Johannes Singler. #ifndef _GLIBCXX_PARALLEL_FIND_H #define _GLIBCXX_PARALLEL_FIND_H 1 #include <bits/stl_algobase.h> #include <parallel/features.h> #include <parallel/parallel.h> #include <parallel/compatibility.h> #include <parallel/equally_split.h> namespace __gnu_parallel { /** * @brief Parallel std::find, switch for different algorithms. * @param __begin1 Begin iterator of first sequence. * @param __end1 End iterator of first sequence. * @param __begin2 Begin iterator of second sequence. Must have same * length as first sequence. * @param __pred Find predicate. * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) * @return Place of finding in both sequences. */ template<typename _RAIter1, typename _RAIter2, typename _Pred, typename _Selector> inline std::pair<_RAIter1, _RAIter2> __find_template(_RAIter1 __begin1, _RAIter1 __end1, _RAIter2 __begin2, _Pred __pred, _Selector __selector) { switch (_Settings::get().find_algorithm) { case GROWING_BLOCKS: return __find_template(__begin1, __end1, __begin2, __pred, __selector, growing_blocks_tag()); case CONSTANT_SIZE_BLOCKS: return __find_template(__begin1, __end1, __begin2, __pred, __selector, constant_size_blocks_tag()); case EQUAL_SPLIT: return __find_template(__begin1, __end1, __begin2, __pred, __selector, equal_split_tag()); default: _GLIBCXX_PARALLEL_ASSERT(false); return std::make_pair(__begin1, __begin2); } } #if _GLIBCXX_FIND_EQUAL_SPLIT /** * @brief Parallel std::find, equal splitting variant. * @param __begin1 Begin iterator of first sequence. * @param __end1 End iterator of first sequence. * @param __begin2 Begin iterator of second sequence. Second __sequence * must have same length as first sequence. * @param __pred Find predicate. * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) * @return Place of finding in both sequences. */ template<typename _RAIter1, typename _RAIter2, typename _Pred, typename _Selector> std::pair<_RAIter1, _RAIter2> __find_template(_RAIter1 __begin1, _RAIter1 __end1, _RAIter2 __begin2, _Pred __pred, _Selector __selector, equal_split_tag) { _GLIBCXX_CALL(__end1 - __begin1) typedef std::iterator_traits<_RAIter1> _TraitsType; typedef typename _TraitsType::difference_type _DifferenceType; typedef typename _TraitsType::value_type _ValueType; _DifferenceType __length = __end1 - __begin1; _DifferenceType __result = __length; _DifferenceType* __borders; omp_lock_t __result_lock; omp_init_lock(&__result_lock); _ThreadIndex __num_threads = __get_max_threads(); # pragma omp parallel num_threads(__num_threads) { # pragma omp single { __num_threads = omp_get_num_threads(); __borders = new _DifferenceType[__num_threads + 1]; __equally_split(__length, __num_threads, __borders); } //single _ThreadIndex __iam = omp_get_thread_num(); _DifferenceType __start = __borders[__iam], __stop = __borders[__iam + 1]; _RAIter1 __i1 = __begin1 + __start; _RAIter2 __i2 = __begin2 + __start; for (_DifferenceType __pos = __start; __pos < __stop; ++__pos) { # pragma omp flush(__result) // Result has been set to something lower. if (__result < __pos) break; if (__selector(__i1, __i2, __pred)) { omp_set_lock(&__result_lock); if (__pos < __result) __result = __pos; omp_unset_lock(&__result_lock); break; } ++__i1; ++__i2; } } //parallel omp_destroy_lock(&__result_lock); delete[] __borders; return std::pair<_RAIter1, _RAIter2>(__begin1 + __result, __begin2 + __result); } #endif #if _GLIBCXX_FIND_GROWING_BLOCKS /** * @brief Parallel std::find, growing block size variant. * @param __begin1 Begin iterator of first sequence. * @param __end1 End iterator of first sequence. * @param __begin2 Begin iterator of second sequence. Second __sequence * must have same length as first sequence. * @param __pred Find predicate. * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) * @return Place of finding in both sequences. * @see __gnu_parallel::_Settings::find_sequential_search_size * @see __gnu_parallel::_Settings::find_scale_factor * * There are two main differences between the growing blocks and * the constant-size blocks variants. * 1. For GB, the block size grows; for CSB, the block size is fixed. * 2. For GB, the blocks are allocated dynamically; * for CSB, the blocks are allocated in a predetermined manner, * namely spacial round-robin. */ template<typename _RAIter1, typename _RAIter2, typename _Pred, typename _Selector> std::pair<_RAIter1, _RAIter2> __find_template(_RAIter1 __begin1, _RAIter1 __end1, _RAIter2 __begin2, _Pred __pred, _Selector __selector, growing_blocks_tag) { _GLIBCXX_CALL(__end1 - __begin1) typedef std::iterator_traits<_RAIter1> _TraitsType; typedef typename _TraitsType::difference_type _DifferenceType; typedef typename _TraitsType::value_type _ValueType; const _Settings& __s = _Settings::get(); _DifferenceType __length = __end1 - __begin1; _DifferenceType __sequential_search_size = std::min<_DifferenceType> (__length, __s.find_sequential_search_size); // Try it sequentially first. std::pair<_RAIter1, _RAIter2> __find_seq_result = __selector._M_sequential_algorithm (__begin1, __begin1 + __sequential_search_size, __begin2, __pred); if (__find_seq_result.first != (__begin1 + __sequential_search_size)) return __find_seq_result; // Index of beginning of next free block (after sequential find). _DifferenceType __next_block_start = __sequential_search_size; _DifferenceType __result = __length; omp_lock_t __result_lock; omp_init_lock(&__result_lock); const float __scale_factor = __s.find_scale_factor; _ThreadIndex __num_threads = __get_max_threads(); # pragma omp parallel shared(__result) num_threads(__num_threads) { # pragma omp single __num_threads = omp_get_num_threads(); // Not within first __k elements -> start parallel. _ThreadIndex __iam = omp_get_thread_num(); _DifferenceType __block_size = std::max<_DifferenceType>(1, __scale_factor * __next_block_start); _DifferenceType __start = __fetch_and_add<_DifferenceType> (&__next_block_start, __block_size); // Get new block, update pointer to next block. _DifferenceType __stop = std::min<_DifferenceType>(__length, __start + __block_size); std::pair<_RAIter1, _RAIter2> __local_result; while (__start < __length) { # pragma omp flush(__result) // Get new value of result. if (__result < __start) { // No chance to find first element. break; } __local_result = __selector._M_sequential_algorithm (__begin1 + __start, __begin1 + __stop, __begin2 + __start, __pred); if (__local_result.first != (__begin1 + __stop)) { omp_set_lock(&__result_lock); if ((__local_result.first - __begin1) < __result) { __result = __local_result.first - __begin1; // Result cannot be in future blocks, stop algorithm. __fetch_and_add<_DifferenceType>(&__next_block_start, __length); } omp_unset_lock(&__result_lock); } _DifferenceType __block_size = std::max<_DifferenceType>(1, __scale_factor * __next_block_start); // Get new block, update pointer to next block. __start = __fetch_and_add<_DifferenceType>(&__next_block_start, __block_size); __stop = std::min<_DifferenceType>(__length, __start + __block_size); } } //parallel omp_destroy_lock(&__result_lock); // Return iterator on found element. return std::pair<_RAIter1, _RAIter2>(__begin1 + __result, __begin2 + __result); } #endif #if _GLIBCXX_FIND_CONSTANT_SIZE_BLOCKS /** * @brief Parallel std::find, constant block size variant. * @param __begin1 Begin iterator of first sequence. * @param __end1 End iterator of first sequence. * @param __begin2 Begin iterator of second sequence. Second __sequence * must have same length as first sequence. * @param __pred Find predicate. * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) * @return Place of finding in both sequences. * @see __gnu_parallel::_Settings::find_sequential_search_size * @see __gnu_parallel::_Settings::find_block_size * There are two main differences between the growing blocks and the * constant-size blocks variants. * 1. For GB, the block size grows; for CSB, the block size is fixed. * 2. For GB, the blocks are allocated dynamically; for CSB, the * blocks are allocated in a predetermined manner, namely spacial * round-robin. */ template<typename _RAIter1, typename _RAIter2, typename _Pred, typename _Selector> std::pair<_RAIter1, _RAIter2> __find_template(_RAIter1 __begin1, _RAIter1 __end1, _RAIter2 __begin2, _Pred __pred, _Selector __selector, constant_size_blocks_tag) { _GLIBCXX_CALL(__end1 - __begin1) typedef std::iterator_traits<_RAIter1> _TraitsType; typedef typename _TraitsType::difference_type _DifferenceType; typedef typename _TraitsType::value_type _ValueType; const _Settings& __s = _Settings::get(); _DifferenceType __length = __end1 - __begin1; _DifferenceType __sequential_search_size = std::min<_DifferenceType> (__length, __s.find_sequential_search_size); // Try it sequentially first. std::pair<_RAIter1, _RAIter2> __find_seq_result = __selector._M_sequential_algorithm (__begin1, __begin1 + __sequential_search_size, __begin2, __pred); if (__find_seq_result.first != (__begin1 + __sequential_search_size)) return __find_seq_result; _DifferenceType __result = __length; omp_lock_t __result_lock; omp_init_lock(&__result_lock); // Not within first __sequential_search_size elements -> start parallel. _ThreadIndex __num_threads = __get_max_threads(); # pragma omp parallel shared(__result) num_threads(__num_threads) { # pragma omp single __num_threads = omp_get_num_threads(); _ThreadIndex __iam = omp_get_thread_num(); _DifferenceType __block_size = __s.find_initial_block_size; // First element of thread's current iteration. _DifferenceType __iteration_start = __sequential_search_size; // Where to work (initialization). _DifferenceType __start = __iteration_start + __iam * __block_size; _DifferenceType __stop = std::min<_DifferenceType>(__length, __start + __block_size); std::pair<_RAIter1, _RAIter2> __local_result; while (__start < __length) { // Get new value of result. # pragma omp flush(__result) // No chance to find first element. if (__result < __start) break; __local_result = __selector._M_sequential_algorithm (__begin1 + __start, __begin1 + __stop, __begin2 + __start, __pred); if (__local_result.first != (__begin1 + __stop)) { omp_set_lock(&__result_lock); if ((__local_result.first - __begin1) < __result) __result = __local_result.first - __begin1; omp_unset_lock(&__result_lock); // Will not find better value in its interval. break; } __iteration_start += __num_threads * __block_size; // Where to work. __start = __iteration_start + __iam * __block_size; __stop = std::min<_DifferenceType>(__length, __start + __block_size); } } //parallel omp_destroy_lock(&__result_lock); // Return iterator on found element. return std::pair<_RAIter1, _RAIter2>(__begin1 + __result, __begin2 + __result); } #endif } // end namespace #endif /* _GLIBCXX_PARALLEL_FIND_H */