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
|
// -*- C++ -*-
// Copyright (C) 2007-2015 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/search.h
* @brief Parallel implementation base for std::search() and
* std::search_n().
* This file is a GNU parallel extension to the Standard C++ Library.
*/
// Written by Felix Putze.
#ifndef _GLIBCXX_PARALLEL_SEARCH_H
#define _GLIBCXX_PARALLEL_SEARCH_H 1
#include <bits/stl_algobase.h>
#include <parallel/parallel.h>
#include <parallel/equally_split.h>
namespace __gnu_parallel
{
/**
* @brief Precalculate __advances for Knuth-Morris-Pratt algorithm.
* @param __elements Begin iterator of sequence to search for.
* @param __length Length of sequence to search for.
* @param __off Returned __offsets.
*/
template<typename _RAIter, typename _DifferenceTp>
void
__calc_borders(_RAIter __elements, _DifferenceTp __length,
_DifferenceTp* __off)
{
typedef _DifferenceTp _DifferenceType;
__off[0] = -1;
if (__length > 1)
__off[1] = 0;
_DifferenceType __k = 0;
for (_DifferenceType __j = 2; __j <= __length; __j++)
{
while ((__k >= 0) && !(__elements[__k] == __elements[__j-1]))
__k = __off[__k];
__off[__j] = ++__k;
}
}
// Generic parallel find algorithm (requires random access iterator).
/** @brief Parallel std::search.
* @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 __pred Find predicate.
* @return Place of finding in first sequences. */
template<typename __RAIter1,
typename __RAIter2,
typename _Pred>
__RAIter1
__search_template(__RAIter1 __begin1, __RAIter1 __end1,
__RAIter2 __begin2, __RAIter2 __end2,
_Pred __pred)
{
typedef std::iterator_traits<__RAIter1> _TraitsType;
typedef typename _TraitsType::difference_type _DifferenceType;
_GLIBCXX_CALL((__end1 - __begin1) + (__end2 - __begin2));
_DifferenceType __pattern_length = __end2 - __begin2;
// Pattern too short.
if(__pattern_length <= 0)
return __end1;
// Last point to start search.
_DifferenceType __input_length = (__end1 - __begin1) - __pattern_length;
// Where is first occurrence of pattern? defaults to end.
_DifferenceType __result = (__end1 - __begin1);
_DifferenceType *__splitters;
// Pattern too long.
if (__input_length < 0)
return __end1;
omp_lock_t __result_lock;
omp_init_lock(&__result_lock);
_ThreadIndex __num_threads = std::max<_DifferenceType>
(1, std::min<_DifferenceType>(__input_length,
__get_max_threads()));
_DifferenceType __advances[__pattern_length];
__calc_borders(__begin2, __pattern_length, __advances);
# pragma omp parallel num_threads(__num_threads)
{
# pragma omp single
{
__num_threads = omp_get_num_threads();
__splitters = new _DifferenceType[__num_threads + 1];
__equally_split(__input_length, __num_threads, __splitters);
}
_ThreadIndex __iam = omp_get_thread_num();
_DifferenceType __start = __splitters[__iam],
__stop = __splitters[__iam + 1];
_DifferenceType __pos_in_pattern = 0;
bool __found_pattern = false;
while (__start <= __stop && !__found_pattern)
{
// Get new value of result.
#pragma omp flush(__result)
// No chance for this thread to find first occurrence.
if (__result < __start)
break;
while (__pred(__begin1[__start + __pos_in_pattern],
__begin2[__pos_in_pattern]))
{
++__pos_in_pattern;
if (__pos_in_pattern == __pattern_length)
{
// Found new candidate for result.
omp_set_lock(&__result_lock);
__result = std::min(__result, __start);
omp_unset_lock(&__result_lock);
__found_pattern = true;
break;
}
}
// Make safe jump.
__start += (__pos_in_pattern - __advances[__pos_in_pattern]);
__pos_in_pattern = (__advances[__pos_in_pattern] < 0
? 0 : __advances[__pos_in_pattern]);
}
} //parallel
omp_destroy_lock(&__result_lock);
delete[] __splitters;
// Return iterator on found element.
return (__begin1 + __result);
}
} // end namespace
#endif /* _GLIBCXX_PARALLEL_SEARCH_H */
|
