402 lines
14 KiB
C++
402 lines
14 KiB
C++
// -*- C++ -*-
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// Copyright (C) 2007, 2008, 2009 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 RandomAccessIterator1,
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typename RandomAccessIterator2,
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typename Pred,
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typename Selector>
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inline std::pair<RandomAccessIterator1, RandomAccessIterator2>
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find_template(RandomAccessIterator1 begin1, RandomAccessIterator1 end1,
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RandomAccessIterator2 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, selector,
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growing_blocks_tag());
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case CONSTANT_SIZE_BLOCKS:
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return find_template(begin1, end1, begin2, pred, selector,
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constant_size_blocks_tag());
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case EQUAL_SPLIT:
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return find_template(begin1, end1, begin2, pred, selector,
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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 RandomAccessIterator1,
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typename RandomAccessIterator2,
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typename Pred,
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typename Selector>
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std::pair<RandomAccessIterator1, RandomAccessIterator2>
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find_template(RandomAccessIterator1 begin1,
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RandomAccessIterator1 end1,
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RandomAccessIterator2 begin2,
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Pred pred,
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Selector selector,
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equal_split_tag)
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{
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_GLIBCXX_CALL(end1 - begin1)
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typedef std::iterator_traits<RandomAccessIterator1> traits_type;
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typedef typename traits_type::difference_type difference_type;
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typedef typename traits_type::value_type value_type;
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difference_type length = end1 - begin1;
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difference_type result = length;
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difference_type* borders;
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omp_lock_t result_lock;
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omp_init_lock(&result_lock);
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thread_index_t 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 difference_type[num_threads + 1];
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equally_split(length, num_threads, borders);
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} //single
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thread_index_t iam = omp_get_thread_num();
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difference_type start = borders[iam], stop = borders[iam + 1];
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RandomAccessIterator1 i1 = begin1 + start;
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RandomAccessIterator2 i2 = begin2 + start;
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for (difference_type 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
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std::pair<RandomAccessIterator1, RandomAccessIterator2>(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_initial_block_size
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* @see __gnu_parallel::_Settings::find_maximum_block_size
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* @see __gnu_parallel::_Settings::find_increasing_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 RandomAccessIterator1,
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typename RandomAccessIterator2,
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typename Pred,
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typename Selector>
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std::pair<RandomAccessIterator1, RandomAccessIterator2>
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find_template(RandomAccessIterator1 begin1, RandomAccessIterator1 end1,
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RandomAccessIterator2 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<RandomAccessIterator1> traits_type;
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typedef typename traits_type::difference_type difference_type;
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typedef typename traits_type::value_type value_type;
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const _Settings& __s = _Settings::get();
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difference_type length = end1 - begin1;
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difference_type sequential_search_size =
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std::min<difference_type>(length, __s.find_sequential_search_size);
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// Try it sequentially first.
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std::pair<RandomAccessIterator1, RandomAccessIterator2> find_seq_result =
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selector.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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// Index of beginning of next free block (after sequential find).
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difference_type next_block_start = sequential_search_size;
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difference_type result = length;
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omp_lock_t result_lock;
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omp_init_lock(&result_lock);
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thread_index_t 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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thread_index_t iam = omp_get_thread_num();
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difference_type block_size = __s.find_initial_block_size;
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difference_type start =
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fetch_and_add<difference_type>(&next_block_start, block_size);
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// Get new block, update pointer to next block.
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difference_type stop =
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std::min<difference_type>(length, start + block_size);
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std::pair<RandomAccessIterator1, RandomAccessIterator2> 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.sequential_algorithm(
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begin1 + start, begin1 + stop, 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<difference_type>(&next_block_start, length);
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}
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omp_unset_lock(&result_lock);
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}
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block_size =
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std::min<difference_type>(block_size * __s.find_increasing_factor,
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__s.find_maximum_block_size);
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// Get new block, update pointer to next block.
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start =
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fetch_and_add<difference_type>(&next_block_start, block_size);
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stop = ((length < (start + block_size))
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? 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<RandomAccessIterator1, RandomAccessIterator2>(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 RandomAccessIterator1,
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typename RandomAccessIterator2,
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typename Pred,
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typename Selector>
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std::pair<RandomAccessIterator1, RandomAccessIterator2>
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find_template(RandomAccessIterator1 begin1, RandomAccessIterator1 end1,
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RandomAccessIterator2 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<RandomAccessIterator1> traits_type;
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typedef typename traits_type::difference_type difference_type;
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typedef typename traits_type::value_type value_type;
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const _Settings& __s = _Settings::get();
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difference_type length = end1 - begin1;
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difference_type sequential_search_size = std::min<difference_type>(
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length, __s.find_sequential_search_size);
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// Try it sequentially first.
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std::pair<RandomAccessIterator1, RandomAccessIterator2> find_seq_result =
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selector.sequential_algorithm(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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difference_type 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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thread_index_t 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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thread_index_t iam = omp_get_thread_num();
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difference_type block_size = __s.find_initial_block_size;
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// First element of thread's current iteration.
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difference_type iteration_start = sequential_search_size;
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// Where to work (initialization).
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difference_type start = iteration_start + iam * block_size;
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difference_type stop =
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std::min<difference_type>(length, start + block_size);
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std::pair<RandomAccessIterator1, RandomAccessIterator2> 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.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<difference_type>(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<RandomAccessIterator1, RandomAccessIterator2>(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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