--- /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/merge.h
+ * @brief Parallel implementation of std::merge().
+ * This file is a GNU parallel extension to the Standard C++ Library.
+ */
+
+// Written by Johannes Singler.
+
+#ifndef _GLIBCXX_PARALLEL_MERGE_H
+#define _GLIBCXX_PARALLEL_MERGE_H 1
+
+#include <parallel/basic_iterator.h>
+#include <bits/stl_algo.h>
+
+namespace __gnu_parallel
+{
+ /** @brief Merge routine being able to merge only the @c __max_length
+ * smallest elements.
+ *
+ * The @c __begin iterators are advanced accordingly, they might not
+ * reach @c __end, in contrast to the usual variant.
+ * @param __begin1 Begin iterator of first sequence.
+ * @param __end1 End iterator of first sequence.
+ * @param __begin2 Begin iterator of second sequence.
+ * @param __end2 End iterator of second sequence.
+ * @param __target Target begin iterator.
+ * @param __max_length Maximum number of elements to merge.
+ * @param __comp Comparator.
+ * @return Output end iterator. */
+ template<typename _RAIter1, typename _RAIter2,
+ typename _OutputIterator, typename _DifferenceTp,
+ typename _Compare>
+ _OutputIterator
+ __merge_advance_usual(_RAIter1& __begin1, _RAIter1 __end1,
+ _RAIter2& __begin2, _RAIter2 __end2,
+ _OutputIterator __target,
+ _DifferenceTp __max_length, _Compare __comp)
+ {
+ typedef _DifferenceTp _DifferenceType;
+ while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0)
+ {
+ // array1[__i1] < array0[i0]
+ if (__comp(*__begin2, *__begin1))
+ *__target++ = *__begin2++;
+ else
+ *__target++ = *__begin1++;
+ --__max_length;
+ }
+
+ if (__begin1 != __end1)
+ {
+ __target = std::copy(__begin1, __begin1 + __max_length, __target);
+ __begin1 += __max_length;
+ }
+ else
+ {
+ __target = std::copy(__begin2, __begin2 + __max_length, __target);
+ __begin2 += __max_length;
+ }
+ return __target;
+ }
+
+ /** @brief Merge routine being able to merge only the @c __max_length
+ * smallest elements.
+ *
+ * The @c __begin iterators are advanced accordingly, they might not
+ * reach @c __end, in contrast to the usual variant.
+ * Specially designed code should allow the compiler to generate
+ * conditional moves instead of branches.
+ * @param __begin1 Begin iterator of first sequence.
+ * @param __end1 End iterator of first sequence.
+ * @param __begin2 Begin iterator of second sequence.
+ * @param __end2 End iterator of second sequence.
+ * @param __target Target begin iterator.
+ * @param __max_length Maximum number of elements to merge.
+ * @param __comp Comparator.
+ * @return Output end iterator. */
+ template<typename _RAIter1, typename _RAIter2,
+ typename _OutputIterator, typename _DifferenceTp,
+ typename _Compare>
+ _OutputIterator
+ __merge_advance_movc(_RAIter1& __begin1, _RAIter1 __end1,
+ _RAIter2& __begin2, _RAIter2 __end2,
+ _OutputIterator __target,
+ _DifferenceTp __max_length, _Compare __comp)
+ {
+ typedef _DifferenceTp _DifferenceType;
+ typedef typename std::iterator_traits<_RAIter1>::value_type
+ _ValueType1;
+ typedef typename std::iterator_traits<_RAIter2>::value_type
+ _ValueType2;
+
+#if _GLIBCXX_ASSERTIONS
+ _GLIBCXX_PARALLEL_ASSERT(__max_length >= 0);
+#endif
+
+ while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0)
+ {
+ _RAIter1 __next1 = __begin1 + 1;
+ _RAIter2 __next2 = __begin2 + 1;
+ _ValueType1 __element1 = *__begin1;
+ _ValueType2 __element2 = *__begin2;
+
+ if (__comp(__element2, __element1))
+ {
+ __element1 = __element2;
+ __begin2 = __next2;
+ }
+ else
+ __begin1 = __next1;
+
+ *__target = __element1;
+
+ ++__target;
+ --__max_length;
+ }
+ if (__begin1 != __end1)
+ {
+ __target = std::copy(__begin1, __begin1 + __max_length, __target);
+ __begin1 += __max_length;
+ }
+ else
+ {
+ __target = std::copy(__begin2, __begin2 + __max_length, __target);
+ __begin2 += __max_length;
+ }
+ return __target;
+ }
+
+ /** @brief Merge routine being able to merge only the @c __max_length
+ * smallest elements.
+ *
+ * The @c __begin iterators are advanced accordingly, they might not
+ * reach @c __end, in contrast to the usual variant.
+ * Static switch on whether to use the conditional-move variant.
+ * @param __begin1 Begin iterator of first sequence.
+ * @param __end1 End iterator of first sequence.
+ * @param __begin2 Begin iterator of second sequence.
+ * @param __end2 End iterator of second sequence.
+ * @param __target Target begin iterator.
+ * @param __max_length Maximum number of elements to merge.
+ * @param __comp Comparator.
+ * @return Output end iterator. */
+ template<typename _RAIter1, typename _RAIter2,
+ typename _OutputIterator, typename _DifferenceTp,
+ typename _Compare>
+ inline _OutputIterator
+ __merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
+ _RAIter2& __begin2, _RAIter2 __end2,
+ _OutputIterator __target, _DifferenceTp __max_length,
+ _Compare __comp)
+ {
+ _GLIBCXX_CALL(__max_length)
+
+ return __merge_advance_movc(__begin1, __end1, __begin2, __end2,
+ __target, __max_length, __comp);
+ }
+
+ /** @brief Merge routine fallback to sequential in case the
+ iterators of the two input sequences are of different type.
+ * @param __begin1 Begin iterator of first sequence.
+ * @param __end1 End iterator of first sequence.
+ * @param __begin2 Begin iterator of second sequence.
+ * @param __end2 End iterator of second sequence.
+ * @param __target Target begin iterator.
+ * @param __max_length Maximum number of elements to merge.
+ * @param __comp Comparator.
+ * @return Output end iterator. */
+ template<typename _RAIter1, typename _RAIter2,
+ typename _RAIter3, typename _Compare>
+ inline _RAIter3
+ __parallel_merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
+ _RAIter2& __begin2,
+ // different iterators, parallel implementation
+ // not available
+ _RAIter2 __end2, _RAIter3 __target, typename
+ std::iterator_traits<_RAIter1>::
+ difference_type __max_length, _Compare __comp)
+ { return __merge_advance(__begin1, __end1, __begin2, __end2, __target,
+ __max_length, __comp); }
+
+ /** @brief Parallel merge routine being able to merge only the @c
+ * __max_length smallest elements.
+ *
+ * The @c __begin iterators are advanced accordingly, they might not
+ * reach @c __end, in contrast to the usual variant.
+ * The functionality is projected onto parallel_multiway_merge.
+ * @param __begin1 Begin iterator of first sequence.
+ * @param __end1 End iterator of first sequence.
+ * @param __begin2 Begin iterator of second sequence.
+ * @param __end2 End iterator of second sequence.
+ * @param __target Target begin iterator.
+ * @param __max_length Maximum number of elements to merge.
+ * @param __comp Comparator.
+ * @return Output end iterator.
+ */
+ template<typename _RAIter1, typename _RAIter3,
+ typename _Compare>
+ inline _RAIter3
+ __parallel_merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
+ _RAIter1& __begin2, _RAIter1 __end2,
+ _RAIter3 __target, typename
+ std::iterator_traits<_RAIter1>::
+ difference_type __max_length, _Compare __comp)
+ {
+ typedef typename
+ std::iterator_traits<_RAIter1>::value_type _ValueType;
+ typedef typename std::iterator_traits<_RAIter1>::
+ difference_type _DifferenceType1 /* == difference_type2 */;
+ typedef typename std::iterator_traits<_RAIter3>::
+ difference_type _DifferenceType3;
+ typedef typename std::pair<_RAIter1, _RAIter1>
+ _IteratorPair;
+
+ _IteratorPair __seqs[2] = { std::make_pair(__begin1, __end1),
+ std::make_pair(__begin2, __end2) };
+ _RAIter3 __target_end = parallel_multiway_merge
+ < /* __stable = */ true, /* __sentinels = */ false>
+ (__seqs, __seqs + 2, __target, multiway_merge_exact_splitting
+ < /* __stable = */ true, _IteratorPair*,
+ _Compare, _DifferenceType1>, __max_length, __comp,
+ omp_get_max_threads());
+
+ return __target_end;
+ }
+} //namespace __gnu_parallel
+
+#endif /* _GLIBCXX_PARALLEL_MERGE_H */
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