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Diffstat (limited to 'i686-linux/include/c++/4.4.3/parallel/quicksort.h')
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1 files changed, 179 insertions, 0 deletions
diff --git a/i686-linux/include/c++/4.4.3/parallel/quicksort.h b/i686-linux/include/c++/4.4.3/parallel/quicksort.h new file mode 100644 index 0000000..712b479 --- /dev/null +++ b/i686-linux/include/c++/4.4.3/parallel/quicksort.h @@ -0,0 +1,179 @@ +// -*- 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/quicksort.h + * @brief Implementation of a unbalanced parallel quicksort (in-place). + * This file is a GNU parallel extension to the Standard C++ Library. + */ + +// Written by Johannes Singler. + +#ifndef _GLIBCXX_PARALLEL_QUICKSORT_H +#define _GLIBCXX_PARALLEL_QUICKSORT_H 1 + +#include <parallel/parallel.h> +#include <parallel/partition.h> + +namespace __gnu_parallel +{ + /** @brief Unbalanced quicksort divide step. + * @param begin Begin iterator of subsequence. + * @param end End iterator of subsequence. + * @param comp Comparator. + * @param pivot_rank Desired rank of the pivot. + * @param num_samples Choose pivot from that many samples. + * @param num_threads Number of threads that are allowed to work on + * this part. + */ + template<typename RandomAccessIterator, typename Comparator> + typename std::iterator_traits<RandomAccessIterator>::difference_type + parallel_sort_qs_divide(RandomAccessIterator begin, + RandomAccessIterator end, + Comparator comp, typename std::iterator_traits + <RandomAccessIterator>::difference_type pivot_rank, + typename std::iterator_traits + <RandomAccessIterator>::difference_type + num_samples, thread_index_t num_threads) + { + typedef std::iterator_traits<RandomAccessIterator> traits_type; + typedef typename traits_type::value_type value_type; + typedef typename traits_type::difference_type difference_type; + + difference_type n = end - begin; + num_samples = std::min(num_samples, n); + + // Allocate uninitialized, to avoid default constructor. + value_type* samples = + static_cast<value_type*>(::operator new(num_samples + * sizeof(value_type))); + + for (difference_type s = 0; s < num_samples; ++s) + { + const unsigned long long index = static_cast<unsigned long long>(s) + * n / num_samples; + ::new(&(samples[s])) value_type(begin[index]); + } + + __gnu_sequential::sort(samples, samples + num_samples, comp); + + value_type& pivot = samples[pivot_rank * num_samples / n]; + + __gnu_parallel::binder2nd<Comparator, value_type, value_type, bool> + pred(comp, pivot); + difference_type split = + parallel_partition(begin, end, pred, num_threads); + + ::operator delete(samples); + + return split; + } + + /** @brief Unbalanced quicksort conquer step. + * @param begin Begin iterator of subsequence. + * @param end End iterator of subsequence. + * @param comp Comparator. + * @param num_threads Number of threads that are allowed to work on + * this part. + */ + template<typename RandomAccessIterator, typename Comparator> + void + parallel_sort_qs_conquer(RandomAccessIterator begin, + RandomAccessIterator end, + Comparator comp, + thread_index_t num_threads) + { + typedef std::iterator_traits<RandomAccessIterator> traits_type; + typedef typename traits_type::value_type value_type; + typedef typename traits_type::difference_type difference_type; + + if (num_threads <= 1) + { + __gnu_sequential::sort(begin, end, comp); + return; + } + + difference_type n = end - begin, pivot_rank; + + if (n <= 1) + return; + + thread_index_t num_threads_left; + + if ((num_threads % 2) == 1) + num_threads_left = num_threads / 2 + 1; + else + num_threads_left = num_threads / 2; + + pivot_rank = n * num_threads_left / num_threads; + + difference_type split = + parallel_sort_qs_divide(begin, end, comp, pivot_rank, + _Settings::get().sort_qs_num_samples_preset, + num_threads); + +#pragma omp parallel sections num_threads(2) + { +#pragma omp section + parallel_sort_qs_conquer(begin, begin + split, + comp, num_threads_left); +#pragma omp section + parallel_sort_qs_conquer(begin + split, end, + comp, num_threads - num_threads_left); + } + } + + + + /** @brief Unbalanced quicksort main call. + * @param begin Begin iterator of input sequence. + * @param end End iterator input sequence, ignored. + * @param comp Comparator. + * @param num_threads Number of threads that are allowed to work on + * this part. + */ + template<typename RandomAccessIterator, typename Comparator> + void + parallel_sort_qs(RandomAccessIterator begin, + RandomAccessIterator end, + Comparator comp, + thread_index_t num_threads) + { + _GLIBCXX_CALL(n) + + typedef std::iterator_traits<RandomAccessIterator> traits_type; + typedef typename traits_type::value_type value_type; + typedef typename traits_type::difference_type difference_type; + + difference_type n = end - begin; + + // At least one element per processor. + if (num_threads > n) + num_threads = static_cast<thread_index_t>(n); + + parallel_sort_qs_conquer(begin, begin + n, comp, num_threads); + } + +} //namespace __gnu_parallel + +#endif /* _GLIBCXX_PARALLEL_QUICKSORT_H */ |