3 // Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the terms
7 // of the GNU General Public License as published by the Free Software
8 // Foundation; either version 3, or (at your option) any later
11 // This library is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
25 /** @file parallel/merge.h
26 * @brief Parallel implementation of std::merge().
27 * This file is a GNU parallel extension to the Standard C++ Library.
30 // Written by Johannes Singler.
32 #ifndef _GLIBCXX_PARALLEL_MERGE_H
33 #define _GLIBCXX_PARALLEL_MERGE_H 1
35 #include <parallel/basic_iterator.h>
36 #include <bits/stl_algo.h>
38 namespace __gnu_parallel
40 /** @brief Merge routine being able to merge only the @__c __max_length
43 * The @__c __begin iterators are advanced accordingly, they might not
44 * reach @__c __end, in contrast to the usual variant.
45 * @param __begin1 Begin iterator of first sequence.
46 * @param __end1 End iterator of first sequence.
47 * @param __begin2 Begin iterator of second sequence.
48 * @param __end2 End iterator of second sequence.
49 * @param __target Target begin iterator.
50 * @param __max_length Maximum number of elements to merge.
51 * @param __comp Comparator.
52 * @return Output end iterator. */
53 template<typename _RAIter1
, typename _RAIter2
,
54 typename _OutputIterator
, typename _DifferenceTp
,
57 __merge_advance_usual(_RAIter1
& __begin1
,
60 _RAIter2 __end2
, _OutputIterator __target
,
61 _DifferenceTp __max_length
, _Compare __comp
)
63 typedef _DifferenceTp _DifferenceType
;
64 while (__begin1
!= __end1
&& __begin2
!= __end2
&& __max_length
> 0)
66 // array1[__i1] < array0[i0]
67 if (__comp(*__begin2
, *__begin1
))
68 *__target
++ = *__begin2
++;
70 *__target
++ = *__begin1
++;
74 if (__begin1
!= __end1
)
76 __target
= std::copy(__begin1
, __begin1
+ __max_length
, __target
);
77 __begin1
+= __max_length
;
81 __target
= std::copy(__begin2
, __begin2
+ __max_length
, __target
);
82 __begin2
+= __max_length
;
87 /** @brief Merge routine being able to merge only the @__c __max_length
90 * The @__c __begin iterators are advanced accordingly, they might not
91 * reach @__c __end, in contrast to the usual variant.
92 * Specially designed code should allow the compiler to generate
93 * conditional moves instead of branches.
94 * @param __begin1 Begin iterator of first sequence.
95 * @param __end1 End iterator of first sequence.
96 * @param __begin2 Begin iterator of second sequence.
97 * @param __end2 End iterator of second sequence.
98 * @param __target Target begin iterator.
99 * @param __max_length Maximum number of elements to merge.
100 * @param __comp Comparator.
101 * @return Output end iterator. */
102 template<typename _RAIter1
, typename _RAIter2
,
103 typename _OutputIterator
, typename _DifferenceTp
,
106 __merge_advance_movc(_RAIter1
& __begin1
,
110 _OutputIterator __target
,
111 _DifferenceTp __max_length
, _Compare __comp
)
113 typedef _DifferenceTp _DifferenceType
;
114 typedef typename
std::iterator_traits
<_RAIter1
>::value_type
116 typedef typename
std::iterator_traits
<_RAIter2
>::value_type
119 #if _GLIBCXX_ASSERTIONS
120 _GLIBCXX_PARALLEL_ASSERT(__max_length
>= 0);
123 while (__begin1
!= __end1
&& __begin2
!= __end2
&& __max_length
> 0)
125 _RAIter1 __next1
= __begin1
+ 1;
126 _RAIter2 __next2
= __begin2
+ 1;
127 value_type1 __element1
= *__begin1
;
128 value_type2 __element2
= *__begin2
;
130 if (__comp(__element2
, __element1
))
132 __element1
= __element2
;
138 *__target
= __element1
;
143 if (__begin1
!= __end1
)
145 __target
= std::copy(__begin1
, __begin1
+ __max_length
, __target
);
146 __begin1
+= __max_length
;
150 __target
= std::copy(__begin2
, __begin2
+ __max_length
, __target
);
151 __begin2
+= __max_length
;
156 /** @brief Merge routine being able to merge only the @__c __max_length
159 * The @__c __begin iterators are advanced accordingly, they might not
160 * reach @__c __end, in contrast to the usual variant.
161 * Static switch on whether to use the conditional-move variant.
162 * @param __begin1 Begin iterator of first sequence.
163 * @param __end1 End iterator of first sequence.
164 * @param __begin2 Begin iterator of second sequence.
165 * @param __end2 End iterator of second sequence.
166 * @param __target Target begin iterator.
167 * @param __max_length Maximum number of elements to merge.
168 * @param __comp Comparator.
169 * @return Output end iterator. */
170 template<typename _RAIter1
, typename _RAIter2
,
171 typename _OutputIterator
, typename _DifferenceTp
,
173 inline _OutputIterator
174 __merge_advance(_RAIter1
& __begin1
, _RAIter1 __end1
,
175 _RAIter2
& __begin2
, _RAIter2 __end2
,
176 _OutputIterator __target
, _DifferenceTp __max_length
,
179 _GLIBCXX_CALL(__max_length
)
181 return __merge_advance_movc(__begin1
, __end1
, __begin2
, __end2
, __target
,
182 __max_length
, __comp
);
185 /** @brief Merge routine fallback to sequential in case the
186 iterators of the two input sequences are of different type.
187 * @param __begin1 Begin iterator of first sequence.
188 * @param __end1 End iterator of first sequence.
189 * @param __begin2 Begin iterator of second sequence.
190 * @param __end2 End iterator of second sequence.
191 * @param __target Target begin iterator.
192 * @param __max_length Maximum number of elements to merge.
193 * @param __comp Comparator.
194 * @return Output end iterator. */
195 template<typename _RAIter1
, typename _RAIter2
,
196 typename _RAIter3
, typename _Compare
>
198 __parallel_merge_advance(_RAIter1
& __begin1
,
201 // different iterators, parallel implementation
204 _RAIter3 __target
, typename
205 std::iterator_traits
<_RAIter1
>::
206 difference_type __max_length
, _Compare __comp
)
207 { return __merge_advance(__begin1
, __end1
, __begin2
, __end2
, __target
,
208 __max_length
, __comp
); }
210 /** @brief Parallel merge routine being able to merge only the @__c
211 * __max_length smallest elements.
213 * The @__c __begin iterators are advanced accordingly, they might not
214 * reach @__c __end, in contrast to the usual variant.
215 * The functionality is projected onto parallel_multiway_merge.
216 * @param __begin1 Begin iterator of first sequence.
217 * @param __end1 End iterator of first sequence.
218 * @param __begin2 Begin iterator of second sequence.
219 * @param __end2 End iterator of second sequence.
220 * @param __target Target begin iterator.
221 * @param __max_length Maximum number of elements to merge.
222 * @param __comp Comparator.
223 * @return Output end iterator.
225 template<typename _RAIter1
, typename _RAIter3
,
228 __parallel_merge_advance(_RAIter1
& __begin1
,
232 _RAIter3 __target
, typename
233 std::iterator_traits
<_RAIter1
>::
234 difference_type __max_length
, _Compare __comp
)
237 std::iterator_traits
<_RAIter1
>::value_type _ValueType
;
238 typedef typename
std::iterator_traits
<_RAIter1
>::
239 difference_type _DifferenceType1
/* == difference_type2 */;
240 typedef typename
std::iterator_traits
<_RAIter3
>::
241 difference_type _DifferenceType3
;
242 typedef typename
std::pair
<_RAIter1
, _RAIter1
>
246 seqs
[2] = { std::make_pair(__begin1
, __end1
),
247 std::make_pair(__begin2
, __end2
) };
249 __target_end
= parallel_multiway_merge
250 < /* __stable = */ true, /* __sentinels = */ false>(
251 seqs
, seqs
+ 2, __target
,
252 multiway_merge_exact_splitting
253 < /* __stable = */ true, _IteratorPair
*,
254 _Compare
, _DifferenceType1
>,
255 __max_length
, __comp
, omp_get_max_threads());
259 } //namespace __gnu_parallel
261 #endif /* _GLIBCXX_PARALLEL_MERGE_H */