--- /dev/null
+// -*- 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 */
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