multiway_merge.h
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// -*- C++ -*-
// 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.
// 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/multiway_merge.h
* @brief Implementation of sequential and parallel multiway merge.
*
* Explanations on the high-speed merging routines in the appendix of
*
* P. Sanders.
* Fast priority queues for cached memory.
* ACM Journal of Experimental Algorithmics, 5, 2000.
*
* This file is a GNU parallel extension to the Standard C++ Library.
*/
// Written by Johannes Singler and Manuel Holtgrewe.
#ifndef _GLIBCXX_PARALLEL_MULTIWAY_MERGE_H
#define _GLIBCXX_PARALLEL_MULTIWAY_MERGE_H
#include <vector>
#include <bits/stl_algo.h>
#include <parallel/features.h>
#include <parallel/parallel.h>
#include <parallel/losertree.h>
#include <parallel/multiseq_selection.h>
#if _GLIBCXX_ASSERTIONS
#include <parallel/checkers.h>
#endif
/** @brief Length of a sequence described by a pair of iterators. */
#define _GLIBCXX_PARALLEL_LENGTH(__s) ((__s).second - (__s).first)
namespace __gnu_parallel
{
template<typename _RAIter1, typename _RAIter2, typename _OutputIterator,
typename _DifferenceTp, typename _Compare>
_OutputIterator
__merge_advance(_RAIter1&, _RAIter1, _RAIter2&, _RAIter2,
_OutputIterator, _DifferenceTp, _Compare);
/** @brief _Iterator wrapper supporting an implicit supremum at the end
* of the sequence, dominating all comparisons.
*
* The implicit supremum comes with a performance cost.
*
* Deriving from _RAIter is not possible since
* _RAIter need not be a class.
*/
template<typename _RAIter, typename _Compare>
class _GuardedIterator
{
private:
/** @brief Current iterator __position. */
_RAIter _M_current;
/** @brief End iterator of the sequence. */
_RAIter _M_end;
/** @brief _Compare. */
_Compare& __comp;
public:
/** @brief Constructor. Sets iterator to beginning of sequence.
* @param __begin Begin iterator of sequence.
* @param __end End iterator of sequence.
* @param __comp Comparator provided for associated overloaded
* compare operators. */
_GuardedIterator(_RAIter __begin, _RAIter __end, _Compare& __comp)
: _M_current(__begin), _M_end(__end), __comp(__comp)
{ }
/** @brief Pre-increment operator.
* @return This. */
_GuardedIterator<_RAIter, _Compare>&
operator++()
{
++_M_current;
return *this;
}
/** @brief Dereference operator.
* @return Referenced element. */
typename std::iterator_traits<_RAIter>::value_type&
operator*()
{ return *_M_current; }
/** @brief Convert to wrapped iterator.
* @return Wrapped iterator. */
operator _RAIter()
{ return _M_current; }
/** @brief Compare two elements referenced by guarded iterators.
* @param __bi1 First iterator.
* @param __bi2 Second iterator.
* @return @c true if less. */
friend bool
operator<(_GuardedIterator<_RAIter, _Compare>& __bi1,
_GuardedIterator<_RAIter, _Compare>& __bi2)
{
if (__bi1._M_current == __bi1._M_end) // __bi1 is sup
return __bi2._M_current == __bi2._M_end; // __bi2 is not sup
if (__bi2._M_current == __bi2._M_end) // __bi2 is sup
return true;
return (__bi1.__comp)(*__bi1, *__bi2); // normal compare
}
/** @brief Compare two elements referenced by guarded iterators.
* @param __bi1 First iterator.
* @param __bi2 Second iterator.
* @return @c True if less equal. */
friend bool
operator<=(_GuardedIterator<_RAIter, _Compare>& __bi1,
_GuardedIterator<_RAIter, _Compare>& __bi2)
{
if (__bi2._M_current == __bi2._M_end) // __bi1 is sup
return __bi1._M_current != __bi1._M_end; // __bi2 is not sup
if (__bi1._M_current == __bi1._M_end) // __bi2 is sup
return false;
return !(__bi1.__comp)(*__bi2, *__bi1); // normal compare
}
};
template<typename _RAIter, typename _Compare>
class _UnguardedIterator
{
private:
/** @brief Current iterator __position. */
_RAIter _M_current;
/** @brief _Compare. */
_Compare& __comp;
public:
/** @brief Constructor. Sets iterator to beginning of sequence.
* @param __begin Begin iterator of sequence.
* @param __end Unused, only for compatibility.
* @param __comp Unused, only for compatibility. */
_UnguardedIterator(_RAIter __begin,
_RAIter /* __end */, _Compare& __comp)
: _M_current(__begin), __comp(__comp)
{ }
/** @brief Pre-increment operator.
* @return This. */
_UnguardedIterator<_RAIter, _Compare>&
operator++()
{
++_M_current;
return *this;
}
/** @brief Dereference operator.
* @return Referenced element. */
typename std::iterator_traits<_RAIter>::value_type&
operator*()
{ return *_M_current; }
/** @brief Convert to wrapped iterator.
* @return Wrapped iterator. */
operator _RAIter()
{ return _M_current; }
/** @brief Compare two elements referenced by unguarded iterators.
* @param __bi1 First iterator.
* @param __bi2 Second iterator.
* @return @c true if less. */
friend bool
operator<(_UnguardedIterator<_RAIter, _Compare>& __bi1,
_UnguardedIterator<_RAIter, _Compare>& __bi2)
{
// Normal compare.
return (__bi1.__comp)(*__bi1, *__bi2);
}
/** @brief Compare two elements referenced by unguarded iterators.
* @param __bi1 First iterator.
* @param __bi2 Second iterator.
* @return @c True if less equal. */
friend bool
operator<=(_UnguardedIterator<_RAIter, _Compare>& __bi1,
_UnguardedIterator<_RAIter, _Compare>& __bi2)
{
// Normal compare.
return !(__bi1.__comp)(*__bi2, *__bi1);
}
};
/** @brief Highly efficient 3-way merging procedure.
*
* Merging is done with the algorithm implementation described by Peter
* Sanders. Basically, the idea is to minimize the number of necessary
* comparison after merging an element. The implementation trick
* that makes this fast is that the order of the sequences is stored
* in the instruction pointer (translated into labels in C++).
*
* This works well for merging up to 4 sequences.
*
* Note that making the merging stable does @a not come at a
* performance hit.
*
* Whether the merging is done guarded or unguarded is selected by the
* used iterator class.
*
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, less equal than the
* total number of elements available.
*
* @return End iterator of output sequence.
*/
template<template<typename RAI, typename C> class iterator,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
_RAIter3
multiway_merge_3_variant(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{
_GLIBCXX_CALL(__length);
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
if (__length == 0)
return __target;
#if _GLIBCXX_ASSERTIONS
_DifferenceTp __orig_length = __length;
#endif
iterator<_RAIter1, _Compare>
__seq0(__seqs_begin[0].first, __seqs_begin[0].second, __comp),
__seq1(__seqs_begin[1].first, __seqs_begin[1].second, __comp),
__seq2(__seqs_begin[2].first, __seqs_begin[2].second, __comp);
if (__seq0 <= __seq1)
{
if (__seq1 <= __seq2)
goto __s012;
else
if (__seq2 < __seq0)
goto __s201;
else
goto __s021;
}
else
{
if (__seq1 <= __seq2)
{
if (__seq0 <= __seq2)
goto __s102;
else
goto __s120;
}
else
goto __s210;
}
#define _GLIBCXX_PARALLEL_MERGE_3_CASE(__a, __b, __c, __c0, __c1) \
__s ## __a ## __b ## __c : \
*__target = *__seq ## __a; \
++__target; \
--__length; \
++__seq ## __a; \
if (__length == 0) goto __finish; \
if (__seq ## __a __c0 __seq ## __b) goto __s ## __a ## __b ## __c; \
if (__seq ## __a __c1 __seq ## __c) goto __s ## __b ## __a ## __c; \
goto __s ## __b ## __c ## __a;
_GLIBCXX_PARALLEL_MERGE_3_CASE(0, 1, 2, <=, <=);
_GLIBCXX_PARALLEL_MERGE_3_CASE(1, 2, 0, <=, < );
_GLIBCXX_PARALLEL_MERGE_3_CASE(2, 0, 1, < , < );
_GLIBCXX_PARALLEL_MERGE_3_CASE(1, 0, 2, < , <=);
_GLIBCXX_PARALLEL_MERGE_3_CASE(0, 2, 1, <=, <=);
_GLIBCXX_PARALLEL_MERGE_3_CASE(2, 1, 0, < , < );
#undef _GLIBCXX_PARALLEL_MERGE_3_CASE
__finish:
;
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(
((_RAIter1)__seq0 - __seqs_begin[0].first) +
((_RAIter1)__seq1 - __seqs_begin[1].first) +
((_RAIter1)__seq2 - __seqs_begin[2].first)
== __orig_length);
#endif
__seqs_begin[0].first = __seq0;
__seqs_begin[1].first = __seq1;
__seqs_begin[2].first = __seq2;
return __target;
}
/**
* @brief Highly efficient 4-way merging procedure.
*
* Merging is done with the algorithm implementation described by Peter
* Sanders. Basically, the idea is to minimize the number of necessary
* comparison after merging an element. The implementation trick
* that makes this fast is that the order of the sequences is stored
* in the instruction pointer (translated into goto labels in C++).
*
* This works well for merging up to 4 sequences.
*
* Note that making the merging stable does @a not come at a
* performance hit.
*
* Whether the merging is done guarded or unguarded is selected by the
* used iterator class.
*
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, less equal than the
* total number of elements available.
*
* @return End iterator of output sequence.
*/
template<template<typename RAI, typename C> class iterator,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
_RAIter3
multiway_merge_4_variant(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{
_GLIBCXX_CALL(__length);
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
iterator<_RAIter1, _Compare>
__seq0(__seqs_begin[0].first, __seqs_begin[0].second, __comp),
__seq1(__seqs_begin[1].first, __seqs_begin[1].second, __comp),
__seq2(__seqs_begin[2].first, __seqs_begin[2].second, __comp),
__seq3(__seqs_begin[3].first, __seqs_begin[3].second, __comp);
#define _GLIBCXX_PARALLEL_DECISION(__a, __b, __c, __d) { \
if (__seq ## __d < __seq ## __a) \
goto __s ## __d ## __a ## __b ## __c; \
if (__seq ## __d < __seq ## __b) \
goto __s ## __a ## __d ## __b ## __c; \
if (__seq ## __d < __seq ## __c) \
goto __s ## __a ## __b ## __d ## __c; \
goto __s ## __a ## __b ## __c ## __d; }
if (__seq0 <= __seq1)
{
if (__seq1 <= __seq2)
_GLIBCXX_PARALLEL_DECISION(0,1,2,3)
else
if (__seq2 < __seq0)
_GLIBCXX_PARALLEL_DECISION(2,0,1,3)
else
_GLIBCXX_PARALLEL_DECISION(0,2,1,3)
}
else
{
if (__seq1 <= __seq2)
{
if (__seq0 <= __seq2)
_GLIBCXX_PARALLEL_DECISION(1,0,2,3)
else
_GLIBCXX_PARALLEL_DECISION(1,2,0,3)
}
else
_GLIBCXX_PARALLEL_DECISION(2,1,0,3)
}
#define _GLIBCXX_PARALLEL_MERGE_4_CASE(__a, __b, __c, __d, \
__c0, __c1, __c2) \
__s ## __a ## __b ## __c ## __d: \
if (__length == 0) goto __finish; \
*__target = *__seq ## __a; \
++__target; \
--__length; \
++__seq ## __a; \
if (__seq ## __a __c0 __seq ## __b) \
goto __s ## __a ## __b ## __c ## __d; \
if (__seq ## __a __c1 __seq ## __c) \
goto __s ## __b ## __a ## __c ## __d; \
if (__seq ## __a __c2 __seq ## __d) \
goto __s ## __b ## __c ## __a ## __d; \
goto __s ## __b ## __c ## __d ## __a;
_GLIBCXX_PARALLEL_MERGE_4_CASE(0, 1, 2, 3, <=, <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(0, 1, 3, 2, <=, <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(0, 2, 1, 3, <=, <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(0, 2, 3, 1, <=, <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(0, 3, 1, 2, <=, <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(0, 3, 2, 1, <=, <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(1, 0, 2, 3, < , <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(1, 0, 3, 2, < , <=, <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(1, 2, 0, 3, <=, < , <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(1, 2, 3, 0, <=, <=, < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(1, 3, 0, 2, <=, < , <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(1, 3, 2, 0, <=, <=, < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(2, 0, 1, 3, < , < , <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(2, 0, 3, 1, < , <=, < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(2, 1, 0, 3, < , < , <=);
_GLIBCXX_PARALLEL_MERGE_4_CASE(2, 1, 3, 0, < , <=, < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(2, 3, 0, 1, <=, < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(2, 3, 1, 0, <=, < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(3, 0, 1, 2, < , < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(3, 0, 2, 1, < , < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(3, 1, 0, 2, < , < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(3, 1, 2, 0, < , < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(3, 2, 0, 1, < , < , < );
_GLIBCXX_PARALLEL_MERGE_4_CASE(3, 2, 1, 0, < , < , < );
#undef _GLIBCXX_PARALLEL_MERGE_4_CASE
#undef _GLIBCXX_PARALLEL_DECISION
__finish:
;
__seqs_begin[0].first = __seq0;
__seqs_begin[1].first = __seq1;
__seqs_begin[2].first = __seq2;
__seqs_begin[3].first = __seq3;
return __target;
}
/** @brief Multi-way merging procedure for a high branching factor,
* guarded case.
*
* This merging variant uses a LoserTree class as selected by <tt>_LT</tt>.
*
* Stability is selected through the used LoserTree class <tt>_LT</tt>.
*
* At least one non-empty sequence is required.
*
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, less equal than the
* total number of elements available.
*
* @return End iterator of output sequence.
*/
template<typename _LT,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
_RAIter3
multiway_merge_loser_tree(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{
_GLIBCXX_CALL(__length)
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIterIterator>
::difference_type _SeqNumber;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
_SeqNumber __k = static_cast<_SeqNumber>(__seqs_end - __seqs_begin);
_LT __lt(__k, __comp);
// Default value for potentially non-default-constructible types.
_ValueType* __arbitrary_element = 0;
for (_SeqNumber __t = 0; __t < __k; ++__t)
{
if(!__arbitrary_element
&& _GLIBCXX_PARALLEL_LENGTH(__seqs_begin[__t]) > 0)
__arbitrary_element = &(*__seqs_begin[__t].first);
}
for (_SeqNumber __t = 0; __t < __k; ++__t)
{
if (__seqs_begin[__t].first == __seqs_begin[__t].second)
__lt.__insert_start(*__arbitrary_element, __t, true);
else
__lt.__insert_start(*__seqs_begin[__t].first, __t, false);
}
__lt.__init();
_SeqNumber __source;
for (_DifferenceType __i = 0; __i < __length; ++__i)
{
//take out
__source = __lt.__get_min_source();
*(__target++) = *(__seqs_begin[__source].first++);
// Feed.
if (__seqs_begin[__source].first == __seqs_begin[__source].second)
__lt.__delete_min_insert(*__arbitrary_element, true);
else
// Replace from same __source.
__lt.__delete_min_insert(*__seqs_begin[__source].first, false);
}
return __target;
}
/** @brief Multi-way merging procedure for a high branching factor,
* unguarded case.
*
* Merging is done using the LoserTree class <tt>_LT</tt>.
*
* Stability is selected by the used LoserTrees.
*
* @pre No input will run out of elements during the merge.
*
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, less equal than the
* total number of elements available.
*
* @return End iterator of output sequence.
*/
template<typename _LT,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp, typename _Compare>
_RAIter3
multiway_merge_loser_tree_unguarded(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
const typename std::iterator_traits<typename std::iterator_traits<
_RAIterIterator>::value_type::first_type>::value_type&
__sentinel,
_DifferenceTp __length,
_Compare __comp)
{
_GLIBCXX_CALL(__length)
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIterIterator>
::difference_type _SeqNumber;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
_SeqNumber __k = __seqs_end - __seqs_begin;
_LT __lt(__k, __sentinel, __comp);
for (_SeqNumber __t = 0; __t < __k; ++__t)
{
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(__seqs_begin[__t].first
!= __seqs_begin[__t].second);
#endif
__lt.__insert_start(*__seqs_begin[__t].first, __t, false);
}
__lt.__init();
_SeqNumber __source;
#if _GLIBCXX_ASSERTIONS
_DifferenceType __i = 0;
#endif
_RAIter3 __target_end = __target + __length;
while (__target < __target_end)
{
// Take out.
__source = __lt.__get_min_source();
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(0 <= __source && __source < __k);
_GLIBCXX_PARALLEL_ASSERT(__i == 0
|| !__comp(*(__seqs_begin[__source].first), *(__target - 1)));
#endif
// Feed.
*(__target++) = *(__seqs_begin[__source].first++);
#if _GLIBCXX_ASSERTIONS
++__i;
#endif
// Replace from same __source.
__lt.__delete_min_insert(*__seqs_begin[__source].first, false);
}
return __target;
}
/** @brief Multi-way merging procedure for a high branching factor,
* requiring sentinels to exist.
*
* @tparam UnguardedLoserTree _Loser Tree variant to use for the unguarded
* merging.
*
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, less equal than the
* total number of elements available.
*
* @return End iterator of output sequence.
*/
template<typename UnguardedLoserTree,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
_RAIter3
multiway_merge_loser_tree_sentinel(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
const typename std::iterator_traits<typename std::iterator_traits<
_RAIterIterator>::value_type::first_type>::value_type&
__sentinel,
_DifferenceTp __length,
_Compare __comp)
{
_GLIBCXX_CALL(__length)
typedef _DifferenceTp _DifferenceType;
typedef std::iterator_traits<_RAIterIterator> _TraitsType;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
_RAIter3 __target_end;
for (_RAIterIterator __s = __seqs_begin; __s != __seqs_end; ++__s)
// Move the sequence ends to the sentinel. This has the
// effect that the sentinel appears to be within the sequence. Then,
// we can use the unguarded variant if we merge out as many
// non-sentinel elements as we have.
++((*__s).second);
__target_end = multiway_merge_loser_tree_unguarded<UnguardedLoserTree>
(__seqs_begin, __seqs_end, __target, __sentinel, __length, __comp);
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(__target_end == __target + __length);
_GLIBCXX_PARALLEL_ASSERT(__is_sorted(__target, __target_end, __comp));
#endif
// Restore the sequence ends so the sentinels are not contained in the
// sequence any more (see comment in loop above).
for (_RAIterIterator __s = __seqs_begin; __s != __seqs_end; ++__s)
--((*__s).second);
return __target_end;
}
/**
* @brief Traits for determining whether the loser tree should
* use pointers or copies.
*
* The field "_M_use_pointer" is used to determine whether to use pointers
* in he loser trees or whether to copy the values into the loser tree.
*
* The default behavior is to use pointers if the data type is 4 times as
* big as the pointer to it.
*
* Specialize for your data type to customize the behavior.
*
* Example:
*
* template<>
* struct _LoserTreeTraits<int>
* { static const bool _M_use_pointer = false; };
*
* template<>
* struct _LoserTreeTraits<heavyweight_type>
* { static const bool _M_use_pointer = true; };
*
* @param _Tp type to give the loser tree traits for.
*/
template <typename _Tp>
struct _LoserTreeTraits
{
/**
* @brief True iff to use pointers instead of values in loser trees.
*
* The default behavior is to use pointers if the data type is four
* times as big as the pointer to it.
*/
static const bool _M_use_pointer = (sizeof(_Tp) > 4 * sizeof(_Tp*));
};
/**
* @brief Switch for 3-way merging with __sentinels turned off.
*
* Note that 3-way merging is always stable!
*/
template<bool __sentinels /*default == false*/,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
struct __multiway_merge_3_variant_sentinel_switch
{
_RAIter3
operator()(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{ return multiway_merge_3_variant<_GuardedIterator>
(__seqs_begin, __seqs_end, __target, __length, __comp); }
};
/**
* @brief Switch for 3-way merging with __sentinels turned on.
*
* Note that 3-way merging is always stable!
*/
template<typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
struct __multiway_merge_3_variant_sentinel_switch<true, _RAIterIterator,
_RAIter3, _DifferenceTp,
_Compare>
{
_RAIter3
operator()(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{ return multiway_merge_3_variant<_UnguardedIterator>
(__seqs_begin, __seqs_end, __target, __length, __comp); }
};
/**
* @brief Switch for 4-way merging with __sentinels turned off.
*
* Note that 4-way merging is always stable!
*/
template<bool __sentinels /*default == false*/,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
struct __multiway_merge_4_variant_sentinel_switch
{
_RAIter3
operator()(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{ return multiway_merge_4_variant<_GuardedIterator>
(__seqs_begin, __seqs_end, __target, __length, __comp); }
};
/**
* @brief Switch for 4-way merging with __sentinels turned on.
*
* Note that 4-way merging is always stable!
*/
template<typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
struct __multiway_merge_4_variant_sentinel_switch<true, _RAIterIterator,
_RAIter3, _DifferenceTp,
_Compare>
{
_RAIter3
operator()(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_DifferenceTp __length, _Compare __comp)
{ return multiway_merge_4_variant<_UnguardedIterator>
(__seqs_begin, __seqs_end, __target, __length, __comp); }
};
/**
* @brief Switch for k-way merging with __sentinels turned on.
*/
template<bool __sentinels,
bool __stable,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
struct __multiway_merge_k_variant_sentinel_switch
{
_RAIter3
operator()(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
const typename std::iterator_traits<typename std::iterator_traits<
_RAIterIterator>::value_type::first_type>::value_type&
__sentinel,
_DifferenceTp __length, _Compare __comp)
{
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
return multiway_merge_loser_tree_sentinel<
typename __gnu_cxx::__conditional_type<
_LoserTreeTraits<_ValueType>::_M_use_pointer,
_LoserTreePointerUnguarded<__stable, _ValueType, _Compare>,
_LoserTreeUnguarded<__stable, _ValueType, _Compare>
>::__type>
(__seqs_begin, __seqs_end, __target, __sentinel, __length, __comp);
}
};
/**
* @brief Switch for k-way merging with __sentinels turned off.
*/
template<bool __stable,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
struct __multiway_merge_k_variant_sentinel_switch<false, __stable,
_RAIterIterator,
_RAIter3, _DifferenceTp,
_Compare>
{
_RAIter3
operator()(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
const typename std::iterator_traits<typename std::iterator_traits<
_RAIterIterator>::value_type::first_type>::value_type&
__sentinel,
_DifferenceTp __length, _Compare __comp)
{
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
return multiway_merge_loser_tree<
typename __gnu_cxx::__conditional_type<
_LoserTreeTraits<_ValueType>::_M_use_pointer,
_LoserTreePointer<__stable, _ValueType, _Compare>,
_LoserTree<__stable, _ValueType, _Compare>
>::__type >(__seqs_begin, __seqs_end, __target, __length, __comp);
}
};
/** @brief Sequential multi-way merging switch.
*
* The _GLIBCXX_PARALLEL_DECISION is based on the branching factor and
* runtime settings.
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, possibly larger than the
* number of elements available.
* @param __sentinel The sequences have __a __sentinel element.
* @return End iterator of output sequence. */
template<bool __stable,
bool __sentinels,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Compare>
_RAIter3
__sequential_multiway_merge(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
const typename std::iterator_traits<typename std::iterator_traits<
_RAIterIterator>::value_type::first_type>::value_type&
__sentinel,
_DifferenceTp __length, _Compare __comp)
{
_GLIBCXX_CALL(__length)
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIterIterator>
::difference_type _SeqNumber;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
#if _GLIBCXX_ASSERTIONS
for (_RAIterIterator __s = __seqs_begin; __s != __seqs_end; ++__s)
{
_GLIBCXX_PARALLEL_ASSERT(__is_sorted((*__s).first,
(*__s).second, __comp));
}
#endif
_DifferenceTp __total_length = 0;
for (_RAIterIterator __s = __seqs_begin; __s != __seqs_end; ++__s)
__total_length += _GLIBCXX_PARALLEL_LENGTH(*__s);
__length = std::min<_DifferenceTp>(__length, __total_length);
if(__length == 0)
return __target;
_RAIter3 __return_target = __target;
_SeqNumber __k = static_cast<_SeqNumber>(__seqs_end - __seqs_begin);
switch (__k)
{
case 0:
break;
case 1:
__return_target = std::copy(__seqs_begin[0].first,
__seqs_begin[0].first + __length,
__target);
__seqs_begin[0].first += __length;
break;
case 2:
__return_target = __merge_advance(__seqs_begin[0].first,
__seqs_begin[0].second,
__seqs_begin[1].first,
__seqs_begin[1].second,
__target, __length, __comp);
break;
case 3:
__return_target = __multiway_merge_3_variant_sentinel_switch
<__sentinels, _RAIterIterator, _RAIter3, _DifferenceTp, _Compare>()
(__seqs_begin, __seqs_end, __target, __length, __comp);
break;
case 4:
__return_target = __multiway_merge_4_variant_sentinel_switch
<__sentinels, _RAIterIterator, _RAIter3, _DifferenceTp, _Compare>()
(__seqs_begin, __seqs_end, __target, __length, __comp);
break;
default:
__return_target = __multiway_merge_k_variant_sentinel_switch
<__sentinels, __stable, _RAIterIterator, _RAIter3, _DifferenceTp,
_Compare>()
(__seqs_begin, __seqs_end, __target, __sentinel, __length, __comp);
break;
}
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(
__is_sorted(__target, __target + __length, __comp));
#endif
return __return_target;
}
/**
* @brief Stable sorting functor.
*
* Used to reduce code instanciation in multiway_merge_sampling_splitting.
*/
template<bool __stable, class _RAIter, class _StrictWeakOrdering>
struct _SamplingSorter
{
void
operator()(_RAIter __first, _RAIter __last, _StrictWeakOrdering __comp)
{ __gnu_sequential::stable_sort(__first, __last, __comp); }
};
/**
* @brief Non-__stable sorting functor.
*
* Used to reduce code instantiation in multiway_merge_sampling_splitting.
*/
template<class _RAIter, class _StrictWeakOrdering>
struct _SamplingSorter<false, _RAIter, _StrictWeakOrdering>
{
void
operator()(_RAIter __first, _RAIter __last, _StrictWeakOrdering __comp)
{ __gnu_sequential::sort(__first, __last, __comp); }
};
/**
* @brief Sampling based splitting for parallel multiway-merge routine.
*/
template<bool __stable,
typename _RAIterIterator,
typename _Compare,
typename _DifferenceType>
void
multiway_merge_sampling_splitting(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_DifferenceType __length,
_DifferenceType __total_length,
_Compare __comp,
std::vector<std::pair<_DifferenceType, _DifferenceType> > *__pieces)
{
typedef typename std::iterator_traits<_RAIterIterator>
::difference_type _SeqNumber;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType;
// __k sequences.
const _SeqNumber __k
= static_cast<_SeqNumber>(__seqs_end - __seqs_begin);
const _ThreadIndex __num_threads = omp_get_num_threads();
const _DifferenceType __num_samples =
__gnu_parallel::_Settings::get().merge_oversampling * __num_threads;
_ValueType* __samples = static_cast<_ValueType*>
(::operator new(sizeof(_ValueType) * __k * __num_samples));
// Sample.
for (_SeqNumber __s = 0; __s < __k; ++__s)
for (_DifferenceType __i = 0; __i < __num_samples; ++__i)
{
_DifferenceType sample_index = static_cast<_DifferenceType>
(_GLIBCXX_PARALLEL_LENGTH(__seqs_begin[__s])
* (double(__i + 1) / (__num_samples + 1))
* (double(__length) / __total_length));
new(&(__samples[__s * __num_samples + __i]))
_ValueType(__seqs_begin[__s].first[sample_index]);
}
// Sort stable or non-stable, depending on value of template parameter
// "__stable".
_SamplingSorter<__stable, _ValueType*, _Compare>()
(__samples, __samples + (__num_samples * __k), __comp);
for (_ThreadIndex __slab = 0; __slab < __num_threads; ++__slab)
// For each slab / processor.
for (_SeqNumber __seq = 0; __seq < __k; ++__seq)
{
// For each sequence.
if (__slab > 0)
__pieces[__slab][__seq].first = std::upper_bound
(__seqs_begin[__seq].first, __seqs_begin[__seq].second,
__samples[__num_samples * __k * __slab / __num_threads],
__comp)
- __seqs_begin[__seq].first;
else
// Absolute beginning.
__pieces[__slab][__seq].first = 0;
if ((__slab + 1) < __num_threads)
__pieces[__slab][__seq].second = std::upper_bound
(__seqs_begin[__seq].first, __seqs_begin[__seq].second,
__samples[__num_samples * __k * (__slab + 1) / __num_threads],
__comp)
- __seqs_begin[__seq].first;
else
// Absolute end.
__pieces[__slab][__seq].second =
_GLIBCXX_PARALLEL_LENGTH(__seqs_begin[__seq]);
}
for (_SeqNumber __s = 0; __s < __k; ++__s)
for (_DifferenceType __i = 0; __i < __num_samples; ++__i)
__samples[__s * __num_samples + __i].~_ValueType();
::operator delete(__samples);
}
/**
* @brief Exact splitting for parallel multiway-merge routine.
*
* None of the passed sequences may be empty.
*/
template<bool __stable,
typename _RAIterIterator,
typename _Compare,
typename _DifferenceType>
void
multiway_merge_exact_splitting(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_DifferenceType __length,
_DifferenceType __total_length,
_Compare __comp,
std::vector<std::pair<_DifferenceType, _DifferenceType> > *__pieces)
{
typedef typename std::iterator_traits<_RAIterIterator>
::difference_type _SeqNumber;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
const bool __tight = (__total_length == __length);
// __k sequences.
const _SeqNumber __k = __seqs_end - __seqs_begin;
const _ThreadIndex __num_threads = omp_get_num_threads();
// (Settings::multiway_merge_splitting
// == __gnu_parallel::_Settings::EXACT).
std::vector<_RAIter1>* __offsets =
new std::vector<_RAIter1>[__num_threads];
std::vector<std::pair<_RAIter1, _RAIter1> > __se(__k);
copy(__seqs_begin, __seqs_end, __se.begin());
_DifferenceType* __borders =
new _DifferenceType[__num_threads + 1];
__equally_split(__length, __num_threads, __borders);
for (_ThreadIndex __s = 0; __s < (__num_threads - 1); ++__s)
{
__offsets[__s].resize(__k);
multiseq_partition(__se.begin(), __se.end(), __borders[__s + 1],
__offsets[__s].begin(), __comp);
// Last one also needed and available.
if (!__tight)
{
__offsets[__num_threads - 1].resize(__k);
multiseq_partition(__se.begin(), __se.end(),
_DifferenceType(__length),
__offsets[__num_threads - 1].begin(),
__comp);
}
}
delete[] __borders;
for (_ThreadIndex __slab = 0; __slab < __num_threads; ++__slab)
{
// For each slab / processor.
for (_SeqNumber __seq = 0; __seq < __k; ++__seq)
{
// For each sequence.
if (__slab == 0)
{
// Absolute beginning.
__pieces[__slab][__seq].first = 0;
}
else
__pieces[__slab][__seq].first =
__pieces[__slab - 1][__seq].second;
if (!__tight || __slab < (__num_threads - 1))
__pieces[__slab][__seq].second =
__offsets[__slab][__seq] - __seqs_begin[__seq].first;
else
{
// __slab == __num_threads - 1
__pieces[__slab][__seq].second =
_GLIBCXX_PARALLEL_LENGTH(__seqs_begin[__seq]);
}
}
}
delete[] __offsets;
}
/** @brief Parallel multi-way merge routine.
*
* The _GLIBCXX_PARALLEL_DECISION is based on the branching factor
* and runtime settings.
*
* Must not be called if the number of sequences is 1.
*
* @tparam _Splitter functor to split input (either __exact or sampling based)
* @tparam __stable Stable merging incurs a performance penalty.
* @tparam __sentinel Ignored.
*
* @param __seqs_begin Begin iterator of iterator pair input sequence.
* @param __seqs_end End iterator of iterator pair input sequence.
* @param __target Begin iterator of output sequence.
* @param __comp Comparator.
* @param __length Maximum length to merge, possibly larger than the
* number of elements available.
* @return End iterator of output sequence.
*/
template<bool __stable,
bool __sentinels,
typename _RAIterIterator,
typename _RAIter3,
typename _DifferenceTp,
typename _Splitter,
typename _Compare>
_RAIter3
parallel_multiway_merge(_RAIterIterator __seqs_begin,
_RAIterIterator __seqs_end,
_RAIter3 __target,
_Splitter __splitter,
_DifferenceTp __length,
_Compare __comp,
_ThreadIndex __num_threads)
{
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(__seqs_end - __seqs_begin > 1);
#endif
_GLIBCXX_CALL(__length)
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIterIterator>
::difference_type _SeqNumber;
typedef typename std::iterator_traits<_RAIterIterator>
::value_type::first_type
_RAIter1;
typedef typename
std::iterator_traits<_RAIter1>::value_type _ValueType;
// Leave only non-empty sequences.
typedef std::pair<_RAIter1, _RAIter1> seq_type;
seq_type* __ne_seqs = new seq_type[__seqs_end - __seqs_begin];
_SeqNumber __k = 0;
_DifferenceType __total_length = 0;
for (_RAIterIterator __raii = __seqs_begin;
__raii != __seqs_end; ++__raii)
{
_DifferenceTp __seq_length = _GLIBCXX_PARALLEL_LENGTH(*__raii);
if(__seq_length > 0)
{
__total_length += __seq_length;
__ne_seqs[__k++] = *__raii;
}
}
_GLIBCXX_CALL(__total_length)
__length = std::min<_DifferenceTp>(__length, __total_length);
if (__total_length == 0 || __k == 0)
{
delete[] __ne_seqs;
return __target;
}
std::vector<std::pair<_DifferenceType, _DifferenceType> >* __pieces;
__num_threads = static_cast<_ThreadIndex>
(std::min<_DifferenceType>(__num_threads, __total_length));
# pragma omp parallel num_threads (__num_threads)
{
# pragma omp single
{
__num_threads = omp_get_num_threads();
// Thread __t will have to merge pieces[__iam][0..__k - 1]
__pieces = new std::vector<
std::pair<_DifferenceType, _DifferenceType> >[__num_threads];
for (_ThreadIndex __s = 0; __s < __num_threads; ++__s)
__pieces[__s].resize(__k);
_DifferenceType __num_samples =
__gnu_parallel::_Settings::get().merge_oversampling
* __num_threads;
__splitter(__ne_seqs, __ne_seqs + __k, __length, __total_length,
__comp, __pieces);
} //single
_ThreadIndex __iam = omp_get_thread_num();
_DifferenceType __target_position = 0;
for (_SeqNumber __c = 0; __c < __k; ++__c)
__target_position += __pieces[__iam][__c].first;
seq_type* __chunks = new seq_type[__k];
for (_SeqNumber __s = 0; __s < __k; ++__s)
__chunks[__s] = std::make_pair(__ne_seqs[__s].first
+ __pieces[__iam][__s].first,
__ne_seqs[__s].first
+ __pieces[__iam][__s].second);
if(__length > __target_position)
__sequential_multiway_merge<__stable, __sentinels>
(__chunks, __chunks + __k, __target + __target_position,
*(__seqs_begin->second), __length - __target_position, __comp);
delete[] __chunks;
} // parallel
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(
__is_sorted(__target, __target + __length, __comp));
#endif
__k = 0;
// Update ends of sequences.
for (_RAIterIterator __raii = __seqs_begin;
__raii != __seqs_end; ++__raii)
{
_DifferenceTp __length = _GLIBCXX_PARALLEL_LENGTH(*__raii);
if(__length > 0)
(*__raii).first += __pieces[__num_threads - 1][__k++].second;
}
delete[] __pieces;
delete[] __ne_seqs;
return __target + __length;
}
/**
* @brief Multiway Merge Frontend.
*
* Merge the sequences specified by seqs_begin and __seqs_end into
* __target. __seqs_begin and __seqs_end must point to a sequence of
* pairs. These pairs must contain an iterator to the beginning
* of a sequence in their first entry and an iterator the _M_end of
* the same sequence in their second entry.
*
* Ties are broken arbitrarily. See stable_multiway_merge for a variant
* that breaks ties by sequence number but is slower.
*
* The first entries of the pairs (i.e. the begin iterators) will be moved
* forward.
*
* The output sequence has to provide enough space for all elements
* that are written to it.
*
* This function will merge the input sequences:
*
* - not stable
* - parallel, depending on the input size and Settings
* - using sampling for splitting
* - not using sentinels
*
* Example:
*
* <pre>
* int sequences[10][10];
* for (int __i = 0; __i < 10; ++__i)
* for (int __j = 0; __i < 10; ++__j)
* sequences[__i][__j] = __j;
*
* int __out[33];
* std::vector<std::pair<int*> > seqs;
* for (int __i = 0; __i < 10; ++__i)
* { seqs.push(std::make_pair<int*>(sequences[__i],
* sequences[__i] + 10)) }
*
* multiway_merge(seqs.begin(), seqs.end(), __target, std::less<int>(), 33);
* </pre>
*
* @see stable_multiway_merge
*
* @pre All input sequences must be sorted.
* @pre Target must provide enough space to merge out length elements or
* the number of elements in all sequences, whichever is smaller.
*
* @post [__target, return __value) contains merged __elements from the
* input sequences.
* @post return __value - __target = min(__length, number of elements in all
* sequences).
*
* @tparam _RAIterPairIterator iterator over sequence
* of pairs of iterators
* @tparam _RAIterOut iterator over target sequence
* @tparam _DifferenceTp difference type for the sequence
* @tparam _Compare strict weak ordering type to compare elements
* in sequences
*
* @param __seqs_begin __begin of sequence __sequence
* @param __seqs_end _M_end of sequence __sequence
* @param __target target sequence to merge to.
* @param __comp strict weak ordering to use for element comparison.
* @param __length Maximum length to merge, possibly larger than the
* number of elements available.
*
* @return _M_end iterator of output sequence
*/
// multiway_merge
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::sequential_tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute multiway merge *sequentially*.
return __sequential_multiway_merge
</* __stable = */ false, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::exact_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ false, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
multiway_merge_exact_splitting</* __stable = */ false,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ false, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::sampling_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ false, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
multiway_merge_exact_splitting</* __stable = */ false,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ false, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
parallel_tag __tag = parallel_tag(0))
{ return multiway_merge(__seqs_begin, __seqs_end, __target, __length,
__comp, exact_tag(__tag.__get_num_threads())); }
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
default_parallel_tag __tag)
{ return multiway_merge(__seqs_begin, __seqs_end, __target, __length,
__comp, exact_tag(__tag.__get_num_threads())); }
// stable_multiway_merge
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::sequential_tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute multiway merge *sequentially*.
return __sequential_multiway_merge
</* __stable = */ true, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::exact_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ true, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
multiway_merge_exact_splitting</* __stable = */ true,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ true, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
sampling_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ true, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
multiway_merge_sampling_splitting</* __stable = */ true,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ true, /* __sentinels = */ false>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
parallel_tag __tag = parallel_tag(0))
{
return stable_multiway_merge
(__seqs_begin, __seqs_end, __target, __length, __comp,
exact_tag(__tag.__get_num_threads()));
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
default_parallel_tag __tag)
{
return stable_multiway_merge
(__seqs_begin, __seqs_end, __target, __length, __comp,
exact_tag(__tag.__get_num_threads()));
}
/**
* @brief Multiway Merge Frontend.
*
* Merge the sequences specified by seqs_begin and __seqs_end into
* __target. __seqs_begin and __seqs_end must point to a sequence of
* pairs. These pairs must contain an iterator to the beginning
* of a sequence in their first entry and an iterator the _M_end of
* the same sequence in their second entry.
*
* Ties are broken arbitrarily. See stable_multiway_merge for a variant
* that breaks ties by sequence number but is slower.
*
* The first entries of the pairs (i.e. the begin iterators) will be moved
* forward accordingly.
*
* The output sequence has to provide enough space for all elements
* that are written to it.
*
* This function will merge the input sequences:
*
* - not stable
* - parallel, depending on the input size and Settings
* - using sampling for splitting
* - using sentinels
*
* You have to take care that the element the _M_end iterator points to is
* readable and contains a value that is greater than any other non-sentinel
* value in all sequences.
*
* Example:
*
* <pre>
* int sequences[10][11];
* for (int __i = 0; __i < 10; ++__i)
* for (int __j = 0; __i < 11; ++__j)
* sequences[__i][__j] = __j; // __last one is sentinel!
*
* int __out[33];
* std::vector<std::pair<int*> > seqs;
* for (int __i = 0; __i < 10; ++__i)
* { seqs.push(std::make_pair<int*>(sequences[__i],
* sequences[__i] + 10)) }
*
* multiway_merge(seqs.begin(), seqs.end(), __target, std::less<int>(), 33);
* </pre>
*
* @pre All input sequences must be sorted.
* @pre Target must provide enough space to merge out length elements or
* the number of elements in all sequences, whichever is smaller.
* @pre For each @c __i, @c __seqs_begin[__i].second must be the end
* marker of the sequence, but also reference the one more __sentinel
* element.
*
* @post [__target, return __value) contains merged __elements from the
* input sequences.
* @post return __value - __target = min(__length, number of elements in all
* sequences).
*
* @see stable_multiway_merge_sentinels
*
* @tparam _RAIterPairIterator iterator over sequence
* of pairs of iterators
* @tparam _RAIterOut iterator over target sequence
* @tparam _DifferenceTp difference type for the sequence
* @tparam _Compare strict weak ordering type to compare elements
* in sequences
*
* @param __seqs_begin __begin of sequence __sequence
* @param __seqs_end _M_end of sequence __sequence
* @param __target target sequence to merge to.
* @param __comp strict weak ordering to use for element comparison.
* @param __length Maximum length to merge, possibly larger than the
* number of elements available.
*
* @return _M_end iterator of output sequence
*/
// multiway_merge_sentinels
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::sequential_tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute multiway merge *sequentially*.
return __sequential_multiway_merge
</* __stable = */ false, /* __sentinels = */ true>
(__seqs_begin, __seqs_end,
__target, *(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::exact_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ false, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
multiway_merge_exact_splitting</* __stable = */ false,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ false, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
sampling_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ false, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
multiway_merge_sampling_splitting</* __stable = */ false,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */false, /* __sentinels = */ true>(
__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
parallel_tag __tag = parallel_tag(0))
{
return multiway_merge_sentinels
(__seqs_begin, __seqs_end, __target, __length, __comp,
exact_tag(__tag.__get_num_threads()));
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
default_parallel_tag __tag)
{
return multiway_merge_sentinels
(__seqs_begin, __seqs_end, __target, __length, __comp,
exact_tag(__tag.__get_num_threads()));
}
// stable_multiway_merge_sentinels
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::sequential_tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute multiway merge *sequentially*.
return __sequential_multiway_merge
</* __stable = */ true, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
__gnu_parallel::exact_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ true, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
multiway_merge_exact_splitting</* __stable = */ true,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ true, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length,
_Compare __comp,
sampling_tag __tag)
{
typedef _DifferenceTp _DifferenceType;
_GLIBCXX_CALL(__seqs_end - __seqs_begin)
// catch special case: no sequences
if (__seqs_begin == __seqs_end)
return __target;
// Execute merge; maybe parallel, depending on the number of merged
// elements and the number of sequences and global thresholds in
// Settings.
if ((__seqs_end - __seqs_begin > 1)
&& _GLIBCXX_PARALLEL_CONDITION(
((__seqs_end - __seqs_begin) >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_k)
&& ((_SequenceIndex)__length >=
__gnu_parallel::_Settings::get().multiway_merge_minimal_n)))
return parallel_multiway_merge
</* __stable = */ true, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
multiway_merge_sampling_splitting</* __stable = */ true,
typename std::iterator_traits<_RAIterPairIterator>
::value_type*, _Compare, _DifferenceTp>,
static_cast<_DifferenceType>(__length), __comp,
__tag.__get_num_threads());
else
return __sequential_multiway_merge
</* __stable = */ true, /* __sentinels = */ true>
(__seqs_begin, __seqs_end, __target,
*(__seqs_begin->second), __length, __comp);
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length,
_Compare __comp,
parallel_tag __tag = parallel_tag(0))
{
return stable_multiway_merge_sentinels
(__seqs_begin, __seqs_end, __target, __length, __comp,
exact_tag(__tag.__get_num_threads()));
}
// public interface
template<typename _RAIterPairIterator,
typename _RAIterOut,
typename _DifferenceTp,
typename _Compare>
_RAIterOut
stable_multiway_merge_sentinels(_RAIterPairIterator __seqs_begin,
_RAIterPairIterator __seqs_end,
_RAIterOut __target,
_DifferenceTp __length, _Compare __comp,
default_parallel_tag __tag)
{
return stable_multiway_merge_sentinels
(__seqs_begin, __seqs_end, __target, __length, __comp,
exact_tag(__tag.__get_num_threads()));
}
}; // namespace __gnu_parallel
#endif /* _GLIBCXX_PARALLEL_MULTIWAY_MERGE_H */