libstdc++
for_each_selectors.h
Go to the documentation of this file.
1 // -*- C++ -*-
2 
3 // Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
4 //
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
9 // version.
10 
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.
15 
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.
19 
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/>.
24 
25 /** @file parallel/for_each_selectors.h
26  * @brief Functors representing different tasks to be plugged into the
27  * generic parallelization methods for embarrassingly parallel functions.
28  * This file is a GNU parallel extension to the Standard C++ Library.
29  */
30 
31 // Written by Felix Putze.
32 
33 #ifndef _GLIBCXX_PARALLEL_FOR_EACH_SELECTORS_H
34 #define _GLIBCXX_PARALLEL_FOR_EACH_SELECTORS_H 1
35 
37 
38 namespace __gnu_parallel
39 {
40  /** @brief Generic __selector for embarrassingly parallel functions. */
41  template<typename _It>
43  {
44  /** @brief _Iterator on last element processed; needed for some
45  * algorithms (e. g. std::transform()).
46  */
48  };
49 
50  /** @brief std::for_each() selector. */
51  template<typename _It>
53  {
54  /** @brief Functor execution.
55  * @param __o Operator.
56  * @param __i iterator referencing object. */
57  template<typename _Op>
58  bool
59  operator()(_Op& __o, _It __i)
60  {
61  __o(*__i);
62  return true;
63  }
64  };
65 
66  /** @brief std::generate() selector. */
67  template<typename _It>
69  {
70  /** @brief Functor execution.
71  * @param __o Operator.
72  * @param __i iterator referencing object. */
73  template<typename _Op>
74  bool
75  operator()(_Op& __o, _It __i)
76  {
77  *__i = __o();
78  return true;
79  }
80  };
81 
82  /** @brief std::fill() selector. */
83  template<typename _It>
85  {
86  /** @brief Functor execution.
87  * @param __v Current value.
88  * @param __i iterator referencing object. */
89  template<typename _ValueType>
90  bool
91  operator()(_ValueType& __v, _It __i)
92  {
93  *__i = __v;
94  return true;
95  }
96  };
97 
98  /** @brief std::transform() __selector, one input sequence variant. */
99  template<typename _It>
101  {
102  /** @brief Functor execution.
103  * @param __o Operator.
104  * @param __i iterator referencing object. */
105  template<typename _Op>
106  bool
107  operator()(_Op& __o, _It __i)
108  {
109  *__i.second = __o(*__i.first);
110  return true;
111  }
112  };
113 
114  /** @brief std::transform() __selector, two input sequences variant. */
115  template<typename _It>
117  {
118  /** @brief Functor execution.
119  * @param __o Operator.
120  * @param __i iterator referencing object. */
121  template<typename _Op>
122  bool
123  operator()(_Op& __o, _It __i)
124  {
125  *__i._M_third = __o(*__i._M_first, *__i._M_second);
126  return true;
127  }
128  };
129 
130  /** @brief std::replace() selector. */
131  template<typename _It, typename _Tp>
133  {
134  /** @brief Value to replace with. */
135  const _Tp& __new_val;
136 
137  /** @brief Constructor
138  * @param __new_val Value to replace with. */
139  explicit
140  __replace_selector(const _Tp &__new_val) : __new_val(__new_val) {}
141 
142  /** @brief Functor execution.
143  * @param __v Current value.
144  * @param __i iterator referencing object. */
145  bool
146  operator()(_Tp& __v, _It __i)
147  {
148  if (*__i == __v)
149  *__i = __new_val;
150  return true;
151  }
152  };
153 
154  /** @brief std::replace() selector. */
155  template<typename _It, typename _Op, typename _Tp>
157  {
158  /** @brief Value to replace with. */
159  const _Tp& __new_val;
160 
161  /** @brief Constructor.
162  * @param __new_val Value to replace with. */
163  explicit
164  __replace_if_selector(const _Tp &__new_val) : __new_val(__new_val) { }
165 
166  /** @brief Functor execution.
167  * @param __o Operator.
168  * @param __i iterator referencing object. */
169  bool
170  operator()(_Op& __o, _It __i)
171  {
172  if (__o(*__i))
173  *__i = __new_val;
174  return true;
175  }
176  };
177 
178  /** @brief std::count() selector. */
179  template<typename _It, typename _Diff>
181  {
182  /** @brief Functor execution.
183  * @param __v Current value.
184  * @param __i iterator referencing object.
185  * @return 1 if count, 0 if does not count. */
186  template<typename _ValueType>
187  _Diff
188  operator()(_ValueType& __v, _It __i)
189  { return (__v == *__i) ? 1 : 0; }
190  };
191 
192  /** @brief std::count_if () selector. */
193  template<typename _It, typename _Diff>
195  {
196  /** @brief Functor execution.
197  * @param __o Operator.
198  * @param __i iterator referencing object.
199  * @return 1 if count, 0 if does not count. */
200  template<typename _Op>
201  _Diff
202  operator()(_Op& __o, _It __i)
203  { return (__o(*__i)) ? 1 : 0; }
204  };
205 
206  /** @brief std::accumulate() selector. */
207  template<typename _It>
209  {
210  /** @brief Functor execution.
211  * @param __o Operator (unused).
212  * @param __i iterator referencing object.
213  * @return The current value. */
214  template<typename _Op>
215  typename std::iterator_traits<_It>::value_type
216  operator()(_Op __o, _It __i)
217  { return *__i; }
218  };
219 
220  /** @brief std::inner_product() selector. */
221  template<typename _It, typename _It2, typename _Tp>
223  {
224  /** @brief Begin iterator of first sequence. */
226 
227  /** @brief Begin iterator of second sequence. */
229 
230  /** @brief Constructor.
231  * @param __b1 Begin iterator of first sequence.
232  * @param __b2 Begin iterator of second sequence. */
233  explicit
234  __inner_product_selector(_It __b1, _It2 __b2)
235  : __begin1_iterator(__b1), __begin2_iterator(__b2) { }
236 
237  /** @brief Functor execution.
238  * @param __mult Multiplication functor.
239  * @param __current iterator referencing object.
240  * @return Inner product elemental __result. */
241  template<typename _Op>
242  _Tp
243  operator()(_Op __mult, _It __current)
244  {
245  typename std::iterator_traits<_It>::difference_type __position
246  = __current - __begin1_iterator;
247  return __mult(*__current, *(__begin2_iterator + __position));
248  }
249  };
250 
251  /** @brief Selector that just returns the passed iterator. */
252  template<typename _It>
254  {
255  /** @brief Functor execution.
256  * @param __o Operator (unused).
257  * @param __i iterator referencing object.
258  * @return Passed iterator. */
259  template<typename _Op>
260  _It
261  operator()(_Op __o, _It __i)
262  { return __i; }
263  };
264 
265  /** @brief Selector that returns the difference between two adjacent
266  * __elements.
267  */
268  template<typename _It>
270  : public __generic_for_each_selector<_It>
271  {
272  template<typename _Op>
273  bool
274  operator()(_Op& __o, _It __i)
275  {
276  typename _It::first_type __go_back_one = __i.first;
277  --__go_back_one;
278  *__i.second = __o(*__i.first, *__go_back_one);
279  return true;
280  }
281  };
282 
283  /** @brief Functor doing nothing
284  *
285  * For some __reduction tasks (this is not a function object, but is
286  * passed as __selector __dummy parameter.
287  */
288  struct _Nothing
289  {
290  /** @brief Functor execution.
291  * @param __i iterator referencing object. */
292  template<typename _It>
293  void
294  operator()(_It __i) { }
295  };
296 
297  /** @brief Reduction function doing nothing. */
299  {
300  bool
301  operator()(bool, bool) const
302  { return true; }
303  };
304 
305  /** @brief Reduction for finding the maximum element, using a comparator. */
306  template<typename _Compare, typename _It>
308  {
309  _Compare& __comp;
310 
311  explicit
312  __min_element_reduct(_Compare &__c) : __comp(__c) { }
313 
314  _It
315  operator()(_It __x, _It __y)
316  { return (__comp(*__x, *__y)) ? __x : __y; }
317  };
318 
319  /** @brief Reduction for finding the maximum element, using a comparator. */
320  template<typename _Compare, typename _It>
322  {
323  _Compare& __comp;
324 
325  explicit
326  __max_element_reduct(_Compare& __c) : __comp(__c) { }
327 
328  _It
329  operator()(_It __x, _It __y)
330  { return (__comp(*__x, *__y)) ? __y : __x; }
331  };
332 
333  /** @brief General reduction, using a binary operator. */
334  template<typename _BinOp>
336  {
337  _BinOp& __binop;
338 
339  explicit
340  __accumulate_binop_reduct(_BinOp& __b) : __binop(__b) { }
341 
342  template<typename _Result, typename _Addend>
343  _Result
344  operator()(const _Result& __x, const _Addend& __y)
345  { return __binop(__x, __y); }
346  };
347 }
348 
349 #endif /* _GLIBCXX_PARALLEL_FOR_EACH_SELECTORS_H */