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// -*- C++ -*- |
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// Copyright (C) 2007-2013 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. |
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// 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. |
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// 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. |
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// 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/>. |
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/** @file parallel/merge.h |
* @brief Parallel implementation of std::merge(). |
* This file is a GNU parallel extension to the Standard C++ Library. |
*/ |
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// Written by Johannes Singler. |
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#ifndef _GLIBCXX_PARALLEL_MERGE_H |
#define _GLIBCXX_PARALLEL_MERGE_H 1 |
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#include <parallel/basic_iterator.h> |
#include <bits/stl_algo.h> |
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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; |
} |
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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; |
} |
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/** @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; |
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#if _GLIBCXX_ASSERTIONS |
_GLIBCXX_PARALLEL_ASSERT(__max_length >= 0); |
#endif |
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while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0) |
{ |
_RAIter1 __next1 = __begin1 + 1; |
_RAIter2 __next2 = __begin2 + 1; |
_ValueType1 __element1 = *__begin1; |
_ValueType2 __element2 = *__begin2; |
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if (__comp(__element2, __element1)) |
{ |
__element1 = __element2; |
__begin2 = __next2; |
} |
else |
__begin1 = __next1; |
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*__target = __element1; |
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++__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; |
} |
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/** @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) |
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return __merge_advance_movc(__begin1, __end1, __begin2, __end2, |
__target, __max_length, __comp); |
} |
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/** @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); } |
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/** @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; |
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_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()); |
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return __target_end; |
} |
} //namespace __gnu_parallel |
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#endif /* _GLIBCXX_PARALLEL_MERGE_H */ |