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multiway_merge.h
// -*- C++ -*- // Copyright (C) 2007-2018 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_PARALLEL_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_PARALLEL_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_PARALLEL_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_PARALLEL_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_PARALLEL_ASSERTIONS _DifferenceType __i = 0; #endif _RAIter3 __target_end = __target + __length; while (__target < __target_end) { // Take out. __source = __lt.__get_min_source(); #if _GLIBCXX_PARALLEL_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_PARALLEL_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_PARALLEL_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_PARALLEL_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_PARALLEL_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_PARALLEL_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_PARALLEL_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 */