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// -*- 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/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 RandomAccessIterator1,
typename RandomAccessIterator2,
typename Pred,
typename Selector>
inline std::pair<RandomAccessIterator1, RandomAccessIterator2>
find_template(RandomAccessIterator1 begin1, RandomAccessIterator1 end1,
RandomAccessIterator2 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 RandomAccessIterator1,
typename RandomAccessIterator2,
typename Pred,
typename Selector>
std::pair<RandomAccessIterator1, RandomAccessIterator2>
find_template(RandomAccessIterator1 begin1,
RandomAccessIterator1 end1,
RandomAccessIterator2 begin2,
Pred pred,
Selector selector,
equal_split_tag)
{
_GLIBCXX_CALL(end1 - begin1)
typedef std::iterator_traits<RandomAccessIterator1> traits_type;
typedef typename traits_type::difference_type difference_type;
typedef typename traits_type::value_type value_type;
difference_type length = end1 - begin1;
difference_type result = length;
difference_type* borders;
omp_lock_t result_lock;
omp_init_lock(&result_lock);
thread_index_t num_threads = get_max_threads();
# pragma omp parallel num_threads(num_threads)
{
# pragma omp single
{
num_threads = omp_get_num_threads();
borders = new difference_type[num_threads + 1];
equally_split(length, num_threads, borders);
} //single
thread_index_t iam = omp_get_thread_num();
difference_type start = borders[iam], stop = borders[iam + 1];
RandomAccessIterator1 i1 = begin1 + start;
RandomAccessIterator2 i2 = begin2 + start;
for (difference_type 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<RandomAccessIterator1, RandomAccessIterator2>(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_initial_block_size
* @see __gnu_parallel::_Settings::find_maximum_block_size
* @see __gnu_parallel::_Settings::find_increasing_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 RandomAccessIterator1,
typename RandomAccessIterator2,
typename Pred,
typename Selector>
std::pair<RandomAccessIterator1, RandomAccessIterator2>
find_template(RandomAccessIterator1 begin1, RandomAccessIterator1 end1,
RandomAccessIterator2 begin2, Pred pred, Selector selector,
growing_blocks_tag)
{
_GLIBCXX_CALL(end1 - begin1)
typedef std::iterator_traits<RandomAccessIterator1> traits_type;
typedef typename traits_type::difference_type difference_type;
typedef typename traits_type::value_type value_type;
const _Settings& __s = _Settings::get();
difference_type length = end1 - begin1;
difference_type sequential_search_size =
std::min<difference_type>(length, __s.find_sequential_search_size);
// Try it sequentially first.
std::pair<RandomAccessIterator1, RandomAccessIterator2> find_seq_result =
selector.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).
difference_type next_block_start = sequential_search_size;
difference_type result = length;
omp_lock_t result_lock;
omp_init_lock(&result_lock);
thread_index_t 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.
thread_index_t iam = omp_get_thread_num();
difference_type block_size = __s.find_initial_block_size;
difference_type start =
fetch_and_add<difference_type>(&next_block_start, block_size);
// Get new block, update pointer to next block.
difference_type stop =
std::min<difference_type>(length, start + block_size);
std::pair<RandomAccessIterator1, RandomAccessIterator2> 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.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<difference_type>(&next_block_start, length);
}
omp_unset_lock(&result_lock);
}
block_size =
std::min<difference_type>(block_size * __s.find_increasing_factor,
__s.find_maximum_block_size);
// Get new block, update pointer to next block.
start =
fetch_and_add<difference_type>(&next_block_start, block_size);
stop = ((length < (start + block_size))
? length : (start + block_size));
}
} //parallel
omp_destroy_lock(&result_lock);
// Return iterator on found element.
return
std::pair<RandomAccessIterator1, RandomAccessIterator2>(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 RandomAccessIterator1,
typename RandomAccessIterator2,
typename Pred,
typename Selector>
std::pair<RandomAccessIterator1, RandomAccessIterator2>
find_template(RandomAccessIterator1 begin1, RandomAccessIterator1 end1,
RandomAccessIterator2 begin2, Pred pred, Selector selector,
constant_size_blocks_tag)
{
_GLIBCXX_CALL(end1 - begin1)
typedef std::iterator_traits<RandomAccessIterator1> traits_type;
typedef typename traits_type::difference_type difference_type;
typedef typename traits_type::value_type value_type;
const _Settings& __s = _Settings::get();
difference_type length = end1 - begin1;
difference_type sequential_search_size = std::min<difference_type>(
length, __s.find_sequential_search_size);
// Try it sequentially first.
std::pair<RandomAccessIterator1, RandomAccessIterator2> find_seq_result =
selector.sequential_algorithm(begin1, begin1 + sequential_search_size,
begin2, pred);
if (find_seq_result.first != (begin1 + sequential_search_size))
return find_seq_result;
difference_type result = length;
omp_lock_t result_lock;
omp_init_lock(&result_lock);
// Not within first sequential_search_size elements -> start parallel.
thread_index_t num_threads = get_max_threads();
# pragma omp parallel shared(result) num_threads(num_threads)
{
# pragma omp single
num_threads = omp_get_num_threads();
thread_index_t iam = omp_get_thread_num();
difference_type block_size = __s.find_initial_block_size;
// First element of thread's current iteration.
difference_type iteration_start = sequential_search_size;
// Where to work (initialization).
difference_type start = iteration_start + iam * block_size;
difference_type stop =
std::min<difference_type>(length, start + block_size);
std::pair<RandomAccessIterator1, RandomAccessIterator2> 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.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<difference_type>(length, start + block_size);
}
} //parallel
omp_destroy_lock(&result_lock);
// Return iterator on found element.
return
std::pair<RandomAccessIterator1, RandomAccessIterator2>(begin1 + result,
begin2 + result);
}
#endif
} // end namespace
#endif /* _GLIBCXX_PARALLEL_FIND_H */
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