libstdc++
set_operations.h
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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
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8 // Foundation; either version 3, or (at your option) any later
9 // version.
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11 // This library is distributed in the hope that it will be useful, but
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14 // General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
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18 // 3.1, as published by the Free Software Foundation.
19 
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23 // <http://www.gnu.org/licenses/>.
24 
25 /**
26  * @file parallel/set_operations.h
27  * @brief Parallel implementations of set operations for random-access
28  * iterators.
29  * This file is a GNU parallel extension to the Standard C++ Library.
30  */
31 
32 // Written by Marius Elvert and Felix Bondarenko.
33 
34 #ifndef _GLIBCXX_PARALLEL_SET_OPERATIONS_H
35 #define _GLIBCXX_PARALLEL_SET_OPERATIONS_H 1
36 
37 #include <omp.h>
38 
39 #include <parallel/settings.h>
41 
42 namespace __gnu_parallel
43 {
44 template<typename InputIterator, typename OutputIterator>
45  OutputIterator
47  std::pair<InputIterator, InputIterator> e, OutputIterator r)
48  {
49  if (b.first != e.first)
50  {
51  do
52  {
53  *r++ = *b.first++;
54  }
55  while (b.first != e.first);
56  }
57  else
58  {
59  while (b.second != e.second)
60  *r++ = *b.second++;
61  }
62  return r;
63  }
64 
65 template<typename InputIterator,
66  typename OutputIterator,
67  typename Comparator>
68  struct symmetric_difference_func
69  {
70  typedef std::iterator_traits<InputIterator> traits_type;
71  typedef typename traits_type::difference_type difference_type;
72  typedef typename std::pair<InputIterator, InputIterator> iterator_pair;
73 
74  symmetric_difference_func(Comparator c) : comp(c) {}
75 
76  Comparator comp;
77 
78  OutputIterator
79  invoke(InputIterator a, InputIterator b,
80  InputIterator c, InputIterator d,
81  OutputIterator r) const
82  {
83  while (a != b && c != d)
84  {
85  if (comp(*a, *c))
86  {
87  *r = *a;
88  ++a;
89  ++r;
90  }
91  else if (comp(*c, *a))
92  {
93  *r = *c;
94  ++c;
95  ++r;
96  }
97  else
98  {
99  ++a;
100  ++c;
101  }
102  }
103  return std::copy(c, d, std::copy(a, b, r));
104  }
105 
106  difference_type
107  count(InputIterator a, InputIterator b,
108  InputIterator c, InputIterator d) const
109  {
110  difference_type counter = 0;
111 
112  while (a != b && c != d)
113  {
114  if (comp(*a, *c))
115  {
116  ++a;
117  ++counter;
118  }
119  else if (comp(*c, *a))
120  {
121  ++c;
122  ++counter;
123  }
124  else
125  {
126  ++a;
127  ++c;
128  }
129  }
130 
131  return counter + (b - a) + (d - c);
132  }
133 
134  OutputIterator
135  first_empty(InputIterator c, InputIterator d, OutputIterator out) const
136  { return std::copy(c, d, out); }
137 
138  OutputIterator
139  second_empty(InputIterator a, InputIterator b, OutputIterator out) const
140  { return std::copy(a, b, out); }
141  };
142 
143 
144 template<typename InputIterator,
145  typename OutputIterator,
146  typename Comparator>
147  struct difference_func
148  {
149  typedef std::iterator_traits<InputIterator> traits_type;
150  typedef typename traits_type::difference_type difference_type;
151  typedef typename std::pair<InputIterator, InputIterator> iterator_pair;
152 
153  difference_func(Comparator c) : comp(c) {}
154 
155  Comparator comp;
156 
157  OutputIterator
158  invoke(InputIterator a, InputIterator b, InputIterator c, InputIterator d,
159  OutputIterator r) const
160  {
161  while (a != b && c != d)
162  {
163  if (comp(*a, *c))
164  {
165  *r = *a;
166  ++a;
167  ++r;
168  }
169  else if (comp(*c, *a))
170  { ++c; }
171  else
172  {
173  ++a;
174  ++c;
175  }
176  }
177  return std::copy(a, b, r);
178  }
179 
180  difference_type
181  count(InputIterator a, InputIterator b,
182  InputIterator c, InputIterator d) const
183  {
184  difference_type counter = 0;
185 
186  while (a != b && c != d)
187  {
188  if (comp(*a, *c))
189  {
190  ++a;
191  ++counter;
192  }
193  else if (comp(*c, *a))
194  { ++c; }
195  else
196  { ++a; ++c; }
197  }
198 
199  return counter + (b - a);
200  }
201 
202  inline OutputIterator
203  first_empty(InputIterator c, InputIterator d, OutputIterator out) const
204  { return out; }
205 
206  inline OutputIterator
207  second_empty(InputIterator a, InputIterator b, OutputIterator out) const
208  { return std::copy(a, b, out); }
209  };
210 
211 
212 template<typename InputIterator,
213  typename OutputIterator,
214  typename Comparator>
215  struct intersection_func
216  {
217  typedef std::iterator_traits<InputIterator> traits_type;
218  typedef typename traits_type::difference_type difference_type;
219  typedef typename std::pair<InputIterator, InputIterator> iterator_pair;
220 
221  intersection_func(Comparator c) : comp(c) {}
222 
223  Comparator comp;
224 
225  OutputIterator
226  invoke(InputIterator a, InputIterator b, InputIterator c, InputIterator d,
227  OutputIterator r) const
228  {
229  while (a != b && c != d)
230  {
231  if (comp(*a, *c))
232  { ++a; }
233  else if (comp(*c, *a))
234  { ++c; }
235  else
236  {
237  *r = *a;
238  ++a;
239  ++c;
240  ++r;
241  }
242  }
243 
244  return r;
245  }
246 
247  difference_type
248  count(InputIterator a, InputIterator b,
249  InputIterator c, InputIterator d) const
250  {
251  difference_type counter = 0;
252 
253  while (a != b && c != d)
254  {
255  if (comp(*a, *c))
256  { ++a; }
257  else if (comp(*c, *a))
258  { ++c; }
259  else
260  {
261  ++a;
262  ++c;
263  ++counter;
264  }
265  }
266 
267  return counter;
268  }
269 
270  inline OutputIterator
271  first_empty(InputIterator c, InputIterator d, OutputIterator out) const
272  { return out; }
273 
274  inline OutputIterator
275  second_empty(InputIterator a, InputIterator b, OutputIterator out) const
276  { return out; }
277  };
278 
279 template<class InputIterator, class OutputIterator, class Comparator>
280  struct union_func
281  {
282  typedef typename std::iterator_traits<InputIterator>::difference_type
283  difference_type;
284 
285  union_func(Comparator c) : comp(c) {}
286 
287  Comparator comp;
288 
289  OutputIterator
290  invoke(InputIterator a, const InputIterator b, InputIterator c,
291  const InputIterator d, OutputIterator r) const
292  {
293  while (a != b && c != d)
294  {
295  if (comp(*a, *c))
296  {
297  *r = *a;
298  ++a;
299  }
300  else if (comp(*c, *a))
301  {
302  *r = *c;
303  ++c;
304  }
305  else
306  {
307  *r = *a;
308  ++a;
309  ++c;
310  }
311  ++r;
312  }
313  return std::copy(c, d, std::copy(a, b, r));
314  }
315 
316  difference_type
317  count(InputIterator a, InputIterator b,
318  InputIterator c, InputIterator d) const
319  {
320  difference_type counter = 0;
321 
322  while (a != b && c != d)
323  {
324  if (comp(*a, *c))
325  { ++a; }
326  else if (comp(*c, *a))
327  { ++c; }
328  else
329  {
330  ++a;
331  ++c;
332  }
333  ++counter;
334  }
335 
336  counter += (b - a);
337  counter += (d - c);
338  return counter;
339  }
340 
341  inline OutputIterator
342  first_empty(InputIterator c, InputIterator d, OutputIterator out) const
343  { return std::copy(c, d, out); }
344 
345  inline OutputIterator
346  second_empty(InputIterator a, InputIterator b, OutputIterator out) const
347  { return std::copy(a, b, out); }
348  };
349 
350 template<typename InputIterator,
351  typename OutputIterator,
352  typename Operation>
353  OutputIterator
354  parallel_set_operation(InputIterator begin1, InputIterator end1,
355  InputIterator begin2, InputIterator end2,
356  OutputIterator result, Operation op)
357  {
358  _GLIBCXX_CALL((end1 - begin1) + (end2 - begin2))
359 
360  typedef std::iterator_traits<InputIterator> traits_type;
361  typedef typename traits_type::difference_type difference_type;
362  typedef typename std::pair<InputIterator, InputIterator> iterator_pair;
363 
364  if (begin1 == end1)
365  return op.first_empty(begin2, end2, result);
366 
367  if (begin2 == end2)
368  return op.second_empty(begin1, end1, result);
369 
370  const difference_type size = (end1 - begin1) + (end2 - begin2);
371 
372  const iterator_pair sequence[ 2 ] =
373  { std::make_pair(begin1, end1), std::make_pair(begin2, end2) } ;
374  OutputIterator return_value = result;
375  difference_type *borders;
376  iterator_pair *block_begins;
377  difference_type* lengths;
378 
379  thread_index_t num_threads =
380  std::min<difference_type>(get_max_threads(),
381  std::min(end1 - begin1, end2 - begin2));
382 
383 # pragma omp parallel num_threads(num_threads)
384  {
385 # pragma omp single
386  {
387  num_threads = omp_get_num_threads();
388 
389  borders = new difference_type[num_threads + 2];
390  equally_split(size, num_threads + 1, borders);
391  block_begins = new iterator_pair[num_threads + 1];
392  // Very start.
393  block_begins[0] = std::make_pair(begin1, begin2);
394  lengths = new difference_type[num_threads];
395  } //single
396 
397  thread_index_t iam = omp_get_thread_num();
398 
399  // Result from multiseq_partition.
400  InputIterator offset[2];
401  const difference_type rank = borders[iam + 1];
402 
403  multiseq_partition(sequence, sequence + 2, rank, offset, op.comp);
404 
405  // allowed to read?
406  // together
407  // *(offset[ 0 ] - 1) == *offset[ 1 ]
408  if (offset[ 0 ] != begin1 && offset[ 1 ] != end2
409  && !op.comp(*(offset[ 0 ] - 1), *offset[ 1 ])
410  && !op.comp(*offset[ 1 ], *(offset[ 0 ] - 1)))
411  {
412  // Avoid split between globally equal elements: move one to
413  // front in first sequence.
414  --offset[ 0 ];
415  }
416 
417  iterator_pair block_end = block_begins[ iam + 1 ] =
418  iterator_pair(offset[ 0 ], offset[ 1 ]);
419 
420  // Make sure all threads have their block_begin result written out.
421 # pragma omp barrier
422 
423  iterator_pair block_begin = block_begins[ iam ];
424 
425  // Begin working for the first block, while the others except
426  // the last start to count.
427  if (iam == 0)
428  {
429  // The first thread can copy already.
430  lengths[ iam ] = op.invoke(block_begin.first, block_end.first,
431  block_begin.second, block_end.second,
432  result)
433  - result;
434  }
435  else
436  {
437  lengths[ iam ] = op.count(block_begin.first, block_end.first,
438  block_begin.second, block_end.second);
439  }
440 
441  // Make sure everyone wrote their lengths.
442 # pragma omp barrier
443 
444  OutputIterator r = result;
445 
446  if (iam == 0)
447  {
448  // Do the last block.
449  for (int i = 0; i < num_threads; ++i)
450  r += lengths[i];
451 
452  block_begin = block_begins[num_threads];
453 
454  // Return the result iterator of the last block.
455  return_value = op.invoke(
456  block_begin.first, end1, block_begin.second, end2, r);
457 
458  }
459  else
460  {
461  for (int i = 0; i < iam; ++i)
462  r += lengths[ i ];
463 
464  // Reset begins for copy pass.
465  op.invoke(block_begin.first, block_end.first,
466  block_begin.second, block_end.second, r);
467  }
468  }
469  return return_value;
470  }
471 
472 
473 template<typename InputIterator,
474  typename OutputIterator,
475  typename Comparator>
476  inline OutputIterator
477  parallel_set_union(InputIterator begin1, InputIterator end1,
478  InputIterator begin2, InputIterator end2,
479  OutputIterator result, Comparator comp)
480  {
481  return parallel_set_operation(begin1, end1, begin2, end2, result,
482  union_func< InputIterator, OutputIterator, Comparator>(comp));
483  }
484 
485 template<typename InputIterator,
486  typename OutputIterator,
487  typename Comparator>
488  inline OutputIterator
489  parallel_set_intersection(InputIterator begin1, InputIterator end1,
490  InputIterator begin2, InputIterator end2,
491  OutputIterator result, Comparator comp)
492  {
493  return parallel_set_operation(begin1, end1, begin2, end2, result,
494  intersection_func<InputIterator, OutputIterator, Comparator>(comp));
495  }
496 
497 template<typename InputIterator,
498  typename OutputIterator,
499  typename Comparator>
500  inline OutputIterator
501  parallel_set_difference(InputIterator begin1, InputIterator end1,
502  InputIterator begin2, InputIterator end2,
503  OutputIterator result, Comparator comp)
504  {
505  return parallel_set_operation(begin1, end1, begin2, end2, result,
506  difference_func<InputIterator, OutputIterator, Comparator>(comp));
507  }
508 
509 template<typename InputIterator,
510  typename OutputIterator,
511  typename Comparator>
512  inline OutputIterator
513  parallel_set_symmetric_difference(InputIterator begin1, InputIterator end1,
514  InputIterator begin2, InputIterator end2,
515  OutputIterator result, Comparator comp)
516  {
517  return parallel_set_operation(begin1, end1, begin2, end2, result,
518  symmetric_difference_func<InputIterator, OutputIterator, Comparator>
519  (comp));
520  }
521 
522 }
523 
524 #endif /* _GLIBCXX_PARALLEL_SET_OPERATIONS_H */