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406 lines
13 KiB
C++
406 lines
13 KiB
C++
// -*- C++ -*-
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// Copyright (C) 2007-2024 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the terms
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// of the GNU General Public License as published by the Free Software
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// Foundation; either version 3, or (at your option) any later
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// version.
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file parallel/find.h
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* @brief Parallel implementation base for std::find(), std::equal()
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* and related functions.
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* This file is a GNU parallel extension to the Standard C++ Library.
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*/
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// Written by Felix Putze and Johannes Singler.
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#ifndef _GLIBCXX_PARALLEL_FIND_H
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#define _GLIBCXX_PARALLEL_FIND_H 1
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#include <bits/stl_algobase.h>
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#include <parallel/features.h>
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#include <parallel/parallel.h>
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#include <parallel/compatibility.h>
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#include <parallel/equally_split.h>
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namespace __gnu_parallel
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{
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/**
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* @brief Parallel std::find, switch for different algorithms.
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* @param __begin1 Begin iterator of first sequence.
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* @param __end1 End iterator of first sequence.
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* @param __begin2 Begin iterator of second sequence. Must have same
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* length as first sequence.
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* @param __pred Find predicate.
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* @param __selector _Functionality (e. g. std::find_if(), std::equal(),...)
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* @return Place of finding in both sequences.
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*/
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template<typename _RAIter1,
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typename _RAIter2,
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typename _Pred,
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typename _Selector>
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inline std::pair<_RAIter1, _RAIter2>
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__find_template(_RAIter1 __begin1, _RAIter1 __end1,
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_RAIter2 __begin2, _Pred __pred, _Selector __selector)
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{
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switch (_Settings::get().find_algorithm)
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{
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case GROWING_BLOCKS:
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return __find_template(__begin1, __end1, __begin2, __pred,
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__selector, growing_blocks_tag());
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case CONSTANT_SIZE_BLOCKS:
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return __find_template(__begin1, __end1, __begin2, __pred,
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__selector, constant_size_blocks_tag());
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case EQUAL_SPLIT:
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return __find_template(__begin1, __end1, __begin2, __pred,
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__selector, equal_split_tag());
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default:
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_GLIBCXX_PARALLEL_ASSERT(false);
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return std::make_pair(__begin1, __begin2);
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}
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}
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#if _GLIBCXX_FIND_EQUAL_SPLIT
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/**
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* @brief Parallel std::find, equal splitting variant.
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* @param __begin1 Begin iterator of first sequence.
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* @param __end1 End iterator of first sequence.
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* @param __begin2 Begin iterator of second sequence. Second __sequence
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* must have same length as first sequence.
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* @param __pred Find predicate.
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* @param __selector _Functionality (e. g. std::find_if(), std::equal(),...)
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* @return Place of finding in both sequences.
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*/
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template<typename _RAIter1,
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typename _RAIter2,
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typename _Pred,
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typename _Selector>
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std::pair<_RAIter1, _RAIter2>
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__find_template(_RAIter1 __begin1, _RAIter1 __end1,
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_RAIter2 __begin2, _Pred __pred,
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_Selector __selector, equal_split_tag)
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{
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_GLIBCXX_CALL(__end1 - __begin1)
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typedef std::iterator_traits<_RAIter1> _TraitsType;
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typedef typename _TraitsType::difference_type _DifferenceType;
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typedef typename _TraitsType::value_type _ValueType;
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_DifferenceType __length = __end1 - __begin1;
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_DifferenceType __result = __length;
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_DifferenceType* __borders;
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omp_lock_t __result_lock;
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omp_init_lock(&__result_lock);
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_ThreadIndex __num_threads = __get_max_threads();
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# pragma omp parallel num_threads(__num_threads)
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{
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# pragma omp single
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{
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__num_threads = omp_get_num_threads();
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__borders = new _DifferenceType[__num_threads + 1];
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__equally_split(__length, __num_threads, __borders);
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} //single
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_ThreadIndex __iam = omp_get_thread_num();
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_DifferenceType __start = __borders[__iam],
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__stop = __borders[__iam + 1];
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_RAIter1 __i1 = __begin1 + __start;
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_RAIter2 __i2 = __begin2 + __start;
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for (_DifferenceType __pos = __start; __pos < __stop; ++__pos)
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{
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# pragma omp flush(__result)
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// Result has been set to something lower.
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if (__result < __pos)
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break;
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if (__selector(__i1, __i2, __pred))
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{
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omp_set_lock(&__result_lock);
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if (__pos < __result)
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__result = __pos;
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omp_unset_lock(&__result_lock);
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break;
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}
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++__i1;
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++__i2;
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}
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} //parallel
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omp_destroy_lock(&__result_lock);
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delete[] __borders;
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return std::pair<_RAIter1, _RAIter2>(__begin1 + __result,
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__begin2 + __result);
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}
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#endif
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#if _GLIBCXX_FIND_GROWING_BLOCKS
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/**
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* @brief Parallel std::find, growing block size variant.
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* @param __begin1 Begin iterator of first sequence.
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* @param __end1 End iterator of first sequence.
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* @param __begin2 Begin iterator of second sequence. Second __sequence
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* must have same length as first sequence.
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* @param __pred Find predicate.
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* @param __selector _Functionality (e. g. std::find_if(), std::equal(),...)
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* @return Place of finding in both sequences.
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* @see __gnu_parallel::_Settings::find_sequential_search_size
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* @see __gnu_parallel::_Settings::find_scale_factor
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*
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* There are two main differences between the growing blocks and
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* the constant-size blocks variants.
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* 1. For GB, the block size grows; for CSB, the block size is fixed.
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* 2. For GB, the blocks are allocated dynamically;
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* for CSB, the blocks are allocated in a predetermined manner,
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* namely spacial round-robin.
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*/
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template<typename _RAIter1,
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typename _RAIter2,
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typename _Pred,
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typename _Selector>
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std::pair<_RAIter1, _RAIter2>
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__find_template(_RAIter1 __begin1, _RAIter1 __end1,
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_RAIter2 __begin2, _Pred __pred, _Selector __selector,
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growing_blocks_tag)
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{
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_GLIBCXX_CALL(__end1 - __begin1)
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typedef std::iterator_traits<_RAIter1> _TraitsType;
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typedef typename _TraitsType::difference_type _DifferenceType;
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typedef typename _TraitsType::value_type _ValueType;
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const _Settings& __s = _Settings::get();
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_DifferenceType __length = __end1 - __begin1;
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_DifferenceType
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__sequential_search_size = std::min<_DifferenceType>
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(__length, __s.find_sequential_search_size);
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// Try it sequentially first.
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std::pair<_RAIter1, _RAIter2>
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__find_seq_result = __selector._M_sequential_algorithm
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(__begin1, __begin1 + __sequential_search_size,
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__begin2, __pred);
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if (__find_seq_result.first != (__begin1 + __sequential_search_size))
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return __find_seq_result;
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// Index of beginning of next free block (after sequential find).
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_DifferenceType __next_block_start = __sequential_search_size;
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_DifferenceType __result = __length;
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omp_lock_t __result_lock;
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omp_init_lock(&__result_lock);
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const float __scale_factor = __s.find_scale_factor;
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_ThreadIndex __num_threads = __get_max_threads();
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# pragma omp parallel shared(__result) num_threads(__num_threads)
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{
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# pragma omp single
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__num_threads = omp_get_num_threads();
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// Not within first __k elements -> start parallel.
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_ThreadIndex __iam = omp_get_thread_num();
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_DifferenceType __block_size =
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std::max<_DifferenceType>(1, __scale_factor * __next_block_start);
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_DifferenceType __start = __fetch_and_add<_DifferenceType>
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(&__next_block_start, __block_size);
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// Get new block, update pointer to next block.
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_DifferenceType __stop =
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std::min<_DifferenceType>(__length, __start + __block_size);
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std::pair<_RAIter1, _RAIter2> __local_result;
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while (__start < __length)
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{
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# pragma omp flush(__result)
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// Get new value of result.
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if (__result < __start)
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{
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// No chance to find first element.
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break;
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}
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__local_result = __selector._M_sequential_algorithm
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(__begin1 + __start, __begin1 + __stop,
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__begin2 + __start, __pred);
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if (__local_result.first != (__begin1 + __stop))
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{
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omp_set_lock(&__result_lock);
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if ((__local_result.first - __begin1) < __result)
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{
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__result = __local_result.first - __begin1;
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// Result cannot be in future blocks, stop algorithm.
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__fetch_and_add<_DifferenceType>(&__next_block_start,
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__length);
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}
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omp_unset_lock(&__result_lock);
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}
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_DifferenceType __block_size =
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std::max<_DifferenceType>(1, __scale_factor * __next_block_start);
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// Get new block, update pointer to next block.
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__start = __fetch_and_add<_DifferenceType>(&__next_block_start,
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__block_size);
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__stop =
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std::min<_DifferenceType>(__length, __start + __block_size);
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}
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} //parallel
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omp_destroy_lock(&__result_lock);
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// Return iterator on found element.
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return
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std::pair<_RAIter1, _RAIter2>(__begin1 + __result,
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__begin2 + __result);
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}
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#endif
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#if _GLIBCXX_FIND_CONSTANT_SIZE_BLOCKS
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/**
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* @brief Parallel std::find, constant block size variant.
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* @param __begin1 Begin iterator of first sequence.
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* @param __end1 End iterator of first sequence.
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* @param __begin2 Begin iterator of second sequence. Second __sequence
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* must have same length as first sequence.
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* @param __pred Find predicate.
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* @param __selector _Functionality (e. g. std::find_if(), std::equal(),...)
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* @return Place of finding in both sequences.
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* @see __gnu_parallel::_Settings::find_sequential_search_size
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* @see __gnu_parallel::_Settings::find_block_size
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* There are two main differences between the growing blocks and the
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* constant-size blocks variants.
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* 1. For GB, the block size grows; for CSB, the block size is fixed.
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* 2. For GB, the blocks are allocated dynamically; for CSB, the
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* blocks are allocated in a predetermined manner, namely spacial
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* round-robin.
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*/
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template<typename _RAIter1,
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typename _RAIter2,
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typename _Pred,
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typename _Selector>
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std::pair<_RAIter1, _RAIter2>
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__find_template(_RAIter1 __begin1, _RAIter1 __end1,
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_RAIter2 __begin2, _Pred __pred, _Selector __selector,
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constant_size_blocks_tag)
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{
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_GLIBCXX_CALL(__end1 - __begin1)
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typedef std::iterator_traits<_RAIter1> _TraitsType;
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typedef typename _TraitsType::difference_type _DifferenceType;
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typedef typename _TraitsType::value_type _ValueType;
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const _Settings& __s = _Settings::get();
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_DifferenceType __length = __end1 - __begin1;
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_DifferenceType __sequential_search_size = std::min<_DifferenceType>
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(__length, __s.find_sequential_search_size);
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// Try it sequentially first.
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std::pair<_RAIter1, _RAIter2>
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__find_seq_result = __selector._M_sequential_algorithm
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(__begin1, __begin1 + __sequential_search_size, __begin2, __pred);
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if (__find_seq_result.first != (__begin1 + __sequential_search_size))
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return __find_seq_result;
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_DifferenceType __result = __length;
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omp_lock_t __result_lock;
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omp_init_lock(&__result_lock);
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// Not within first __sequential_search_size elements -> start parallel.
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_ThreadIndex __num_threads = __get_max_threads();
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# pragma omp parallel shared(__result) num_threads(__num_threads)
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{
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# pragma omp single
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__num_threads = omp_get_num_threads();
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_ThreadIndex __iam = omp_get_thread_num();
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_DifferenceType __block_size = __s.find_initial_block_size;
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// First element of thread's current iteration.
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_DifferenceType __iteration_start = __sequential_search_size;
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// Where to work (initialization).
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_DifferenceType __start = __iteration_start + __iam * __block_size;
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_DifferenceType __stop = std::min<_DifferenceType>(__length,
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__start
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+ __block_size);
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std::pair<_RAIter1, _RAIter2> __local_result;
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while (__start < __length)
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{
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// Get new value of result.
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# pragma omp flush(__result)
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// No chance to find first element.
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if (__result < __start)
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break;
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__local_result = __selector._M_sequential_algorithm
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(__begin1 + __start, __begin1 + __stop,
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__begin2 + __start, __pred);
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if (__local_result.first != (__begin1 + __stop))
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{
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omp_set_lock(&__result_lock);
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if ((__local_result.first - __begin1) < __result)
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__result = __local_result.first - __begin1;
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omp_unset_lock(&__result_lock);
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// Will not find better value in its interval.
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break;
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}
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__iteration_start += __num_threads * __block_size;
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// Where to work.
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__start = __iteration_start + __iam * __block_size;
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__stop = std::min<_DifferenceType>(__length,
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__start + __block_size);
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}
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} //parallel
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omp_destroy_lock(&__result_lock);
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// Return iterator on found element.
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return std::pair<_RAIter1, _RAIter2>(__begin1 + __result,
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__begin2 + __result);
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}
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#endif
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} // end namespace
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#endif /* _GLIBCXX_PARALLEL_FIND_H */
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