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Diffstat (limited to 'libstdc++-v3/include/parallel/merge.h')
| -rw-r--r-- | libstdc++-v3/include/parallel/merge.h | 251 |
1 files changed, 251 insertions, 0 deletions
diff --git a/libstdc++-v3/include/parallel/merge.h b/libstdc++-v3/include/parallel/merge.h new file mode 100644 index 000000000..a19e996a0 --- /dev/null +++ b/libstdc++-v3/include/parallel/merge.h @@ -0,0 +1,251 @@ +// -*- 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 */ |