1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
|
// -*- C++ -*-
// Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
// Foundation; either version 3, or (at your option) any later
// version.
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file parallel/merge.h
* @brief Parallel implementation of std::merge().
* This file is a GNU parallel extension to the Standard C++ Library.
*/
// Written by Johannes Singler.
#ifndef _GLIBCXX_PARALLEL_MERGE_H
#define _GLIBCXX_PARALLEL_MERGE_H 1
#include <parallel/basic_iterator.h>
#include <bits/stl_algo.h>
namespace __gnu_parallel
{
/** @brief Merge routine being able to merge only the @c __max_length
* smallest elements.
*
* The @c __begin iterators are advanced accordingly, they might not
* reach @c __end, in contrast to the usual variant.
* @param __begin1 Begin iterator of first sequence.
* @param __end1 End iterator of first sequence.
* @param __begin2 Begin iterator of second sequence.
* @param __end2 End iterator of second sequence.
* @param __target Target begin iterator.
* @param __max_length Maximum number of elements to merge.
* @param __comp Comparator.
* @return Output end iterator. */
template<typename _RAIter1, typename _RAIter2,
typename _OutputIterator, typename _DifferenceTp,
typename _Compare>
_OutputIterator
__merge_advance_usual(_RAIter1& __begin1, _RAIter1 __end1,
_RAIter2& __begin2, _RAIter2 __end2,
_OutputIterator __target,
_DifferenceTp __max_length, _Compare __comp)
{
typedef _DifferenceTp _DifferenceType;
while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0)
{
// array1[__i1] < array0[i0]
if (__comp(*__begin2, *__begin1))
*__target++ = *__begin2++;
else
*__target++ = *__begin1++;
--__max_length;
}
if (__begin1 != __end1)
{
__target = std::copy(__begin1, __begin1 + __max_length, __target);
__begin1 += __max_length;
}
else
{
__target = std::copy(__begin2, __begin2 + __max_length, __target);
__begin2 += __max_length;
}
return __target;
}
/** @brief Merge routine being able to merge only the @c __max_length
* smallest elements.
*
* The @c __begin iterators are advanced accordingly, they might not
* reach @c __end, in contrast to the usual variant.
* Specially designed code should allow the compiler to generate
* conditional moves instead of branches.
* @param __begin1 Begin iterator of first sequence.
* @param __end1 End iterator of first sequence.
* @param __begin2 Begin iterator of second sequence.
* @param __end2 End iterator of second sequence.
* @param __target Target begin iterator.
* @param __max_length Maximum number of elements to merge.
* @param __comp Comparator.
* @return Output end iterator. */
template<typename _RAIter1, typename _RAIter2,
typename _OutputIterator, typename _DifferenceTp,
typename _Compare>
_OutputIterator
__merge_advance_movc(_RAIter1& __begin1, _RAIter1 __end1,
_RAIter2& __begin2, _RAIter2 __end2,
_OutputIterator __target,
_DifferenceTp __max_length, _Compare __comp)
{
typedef _DifferenceTp _DifferenceType;
typedef typename std::iterator_traits<_RAIter1>::value_type
_ValueType1;
typedef typename std::iterator_traits<_RAIter2>::value_type
_ValueType2;
#if _GLIBCXX_ASSERTIONS
_GLIBCXX_PARALLEL_ASSERT(__max_length >= 0);
#endif
while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0)
{
_RAIter1 __next1 = __begin1 + 1;
_RAIter2 __next2 = __begin2 + 1;
_ValueType1 __element1 = *__begin1;
_ValueType2 __element2 = *__begin2;
if (__comp(__element2, __element1))
{
__element1 = __element2;
__begin2 = __next2;
}
else
__begin1 = __next1;
*__target = __element1;
++__target;
--__max_length;
}
if (__begin1 != __end1)
{
__target = std::copy(__begin1, __begin1 + __max_length, __target);
__begin1 += __max_length;
}
else
{
__target = std::copy(__begin2, __begin2 + __max_length, __target);
__begin2 += __max_length;
}
return __target;
}
/** @brief Merge routine being able to merge only the @c __max_length
* smallest elements.
*
* The @c __begin iterators are advanced accordingly, they might not
* reach @c __end, in contrast to the usual variant.
* Static switch on whether to use the conditional-move variant.
* @param __begin1 Begin iterator of first sequence.
* @param __end1 End iterator of first sequence.
* @param __begin2 Begin iterator of second sequence.
* @param __end2 End iterator of second sequence.
* @param __target Target begin iterator.
* @param __max_length Maximum number of elements to merge.
* @param __comp Comparator.
* @return Output end iterator. */
template<typename _RAIter1, typename _RAIter2,
typename _OutputIterator, typename _DifferenceTp,
typename _Compare>
inline _OutputIterator
__merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
_RAIter2& __begin2, _RAIter2 __end2,
_OutputIterator __target, _DifferenceTp __max_length,
_Compare __comp)
{
_GLIBCXX_CALL(__max_length)
return __merge_advance_movc(__begin1, __end1, __begin2, __end2,
__target, __max_length, __comp);
}
/** @brief Merge routine fallback to sequential in case the
iterators of the two input sequences are of different type.
* @param __begin1 Begin iterator of first sequence.
* @param __end1 End iterator of first sequence.
* @param __begin2 Begin iterator of second sequence.
* @param __end2 End iterator of second sequence.
* @param __target Target begin iterator.
* @param __max_length Maximum number of elements to merge.
* @param __comp Comparator.
* @return Output end iterator. */
template<typename _RAIter1, typename _RAIter2,
typename _RAIter3, typename _Compare>
inline _RAIter3
__parallel_merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
_RAIter2& __begin2,
// different iterators, parallel implementation
// not available
_RAIter2 __end2, _RAIter3 __target, typename
std::iterator_traits<_RAIter1>::
difference_type __max_length, _Compare __comp)
{ return __merge_advance(__begin1, __end1, __begin2, __end2, __target,
__max_length, __comp); }
/** @brief Parallel merge routine being able to merge only the @c
* __max_length smallest elements.
*
* The @c __begin iterators are advanced accordingly, they might not
* reach @c __end, in contrast to the usual variant.
* The functionality is projected onto parallel_multiway_merge.
* @param __begin1 Begin iterator of first sequence.
* @param __end1 End iterator of first sequence.
* @param __begin2 Begin iterator of second sequence.
* @param __end2 End iterator of second sequence.
* @param __target Target begin iterator.
* @param __max_length Maximum number of elements to merge.
* @param __comp Comparator.
* @return Output end iterator.
*/
template<typename _RAIter1, typename _RAIter3,
typename _Compare>
inline _RAIter3
__parallel_merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
_RAIter1& __begin2, _RAIter1 __end2,
_RAIter3 __target, typename
std::iterator_traits<_RAIter1>::
difference_type __max_length, _Compare __comp)
{
typedef typename
std::iterator_traits<_RAIter1>::value_type _ValueType;
typedef typename std::iterator_traits<_RAIter1>::
difference_type _DifferenceType1 /* == difference_type2 */;
typedef typename std::iterator_traits<_RAIter3>::
difference_type _DifferenceType3;
typedef typename std::pair<_RAIter1, _RAIter1>
_IteratorPair;
_IteratorPair __seqs[2] = { std::make_pair(__begin1, __end1),
std::make_pair(__begin2, __end2) };
_RAIter3 __target_end = parallel_multiway_merge
< /* __stable = */ true, /* __sentinels = */ false>
(__seqs, __seqs + 2, __target, multiway_merge_exact_splitting
< /* __stable = */ true, _IteratorPair*,
_Compare, _DifferenceType1>, __max_length, __comp,
omp_get_max_threads());
return __target_end;
}
} //namespace __gnu_parallel
#endif /* _GLIBCXX_PARALLEL_MERGE_H */
|
