11.2.0/parallel/merge.h

// -*- C++ -*-

// Copyright (C) 2007-2021 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_PARALLEL_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 */
Revision:	1166
Committed:	Tue Oct 26 14:22:36 2021 UTC (4 years ago) by rossy
Content type:	text/x-chdr
File size:	9578 byte(s)
Log Message:	Daodan: Replace MinGW build env with an up-to-date MSYS2 env
#	Content
1	// -- C++ --
2
3	// Copyright (C) 2007-2021 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/merge.h
26	* @brief Parallel implementation of std::merge().
27	* This file is a GNU parallel extension to the Standard C++ Library.
28	*/
29
30	// Written by Johannes Singler.
31
32	#ifndef _GLIBCXX_PARALLEL_MERGE_H
33	#define _GLIBCXX_PARALLEL_MERGE_H 1
34
35	#include <parallel/basic_iterator.h>
36	#include <bits/stl_algo.h>
37
38	namespace __gnu_parallel
39	{
40	/** @brief Merge routine being able to merge only the @c __max_length
41	* smallest elements.
42	*
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,
55	typename _Compare>
56	_OutputIterator
57	__merge_advance_usual(_RAIter1& __begin1, _RAIter1 __end1,
58	_RAIter2& __begin2, _RAIter2 __end2,
59	_OutputIterator __target,
60	_DifferenceTp __max_length, _Compare __comp)
61	{
62	typedef _DifferenceTp _DifferenceType;
63	while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0)
64	{
65	// array1[__i1] < array0[i0]
66	if (__comp(__begin2, __begin1))
67	__target++ = __begin2++;
68	else
69	__target++ = __begin1++;
70	--__max_length;
71	}
72
73	if (__begin1 != __end1)
74	{
75	__target = std::copy(__begin1, __begin1 + __max_length, __target);
76	__begin1 += __max_length;
77	}
78	else
79	{
80	__target = std::copy(__begin2, __begin2 + __max_length, __target);
81	__begin2 += __max_length;
82	}
83	return __target;
84	}
85
86	/** @brief Merge routine being able to merge only the @c __max_length
87	* smallest elements.
88	*
89	* The @c __begin iterators are advanced accordingly, they might not
90	* reach @c __end, in contrast to the usual variant.
91	* Specially designed code should allow the compiler to generate
92	* conditional moves instead of branches.
93	* @param __begin1 Begin iterator of first sequence.
94	* @param __end1 End iterator of first sequence.
95	* @param __begin2 Begin iterator of second sequence.
96	* @param __end2 End iterator of second sequence.
97	* @param __target Target begin iterator.
98	* @param __max_length Maximum number of elements to merge.
99	* @param __comp Comparator.
100	* @return Output end iterator. */
101	template<typename _RAIter1, typename _RAIter2,
102	typename _OutputIterator, typename _DifferenceTp,
103	typename _Compare>
104	_OutputIterator
105	__merge_advance_movc(_RAIter1& __begin1, _RAIter1 __end1,
106	_RAIter2& __begin2, _RAIter2 __end2,
107	_OutputIterator __target,
108	_DifferenceTp __max_length, _Compare __comp)
109	{
110	typedef _DifferenceTp _DifferenceType;
111	typedef typename std::iterator_traits<_RAIter1>::value_type
112	_ValueType1;
113	typedef typename std::iterator_traits<_RAIter2>::value_type
114	_ValueType2;
115
116	#if _GLIBCXX_PARALLEL_ASSERTIONS
117	_GLIBCXX_PARALLEL_ASSERT(__max_length >= 0);
118	#endif
119
120	while (__begin1 != __end1 && __begin2 != __end2 && __max_length > 0)
121	{
122	_RAIter1 __next1 = __begin1 + 1;
123	_RAIter2 __next2 = __begin2 + 1;
124	_ValueType1 __element1 = *__begin1;
125	_ValueType2 __element2 = *__begin2;
126
127	if (__comp(__element2, __element1))
128	{
129	__element1 = __element2;
130	__begin2 = __next2;
131	}
132	else
133	__begin1 = __next1;
134
135	*__target = __element1;
136
137	++__target;
138	--__max_length;
139	}
140	if (__begin1 != __end1)
141	{
142	__target = std::copy(__begin1, __begin1 + __max_length, __target);
143	__begin1 += __max_length;
144	}
145	else
146	{
147	__target = std::copy(__begin2, __begin2 + __max_length, __target);
148	__begin2 += __max_length;
149	}
150	return __target;
151	}
152
153	/** @brief Merge routine being able to merge only the @c __max_length
154	* smallest elements.
155	*
156	* The @c __begin iterators are advanced accordingly, they might not
157	* reach @c __end, in contrast to the usual variant.
158	* Static switch on whether to use the conditional-move variant.
159	* @param __begin1 Begin iterator of first sequence.
160	* @param __end1 End iterator of first sequence.
161	* @param __begin2 Begin iterator of second sequence.
162	* @param __end2 End iterator of second sequence.
163	* @param __target Target begin iterator.
164	* @param __max_length Maximum number of elements to merge.
165	* @param __comp Comparator.
166	* @return Output end iterator. */
167	template<typename _RAIter1, typename _RAIter2,
168	typename _OutputIterator, typename _DifferenceTp,
169	typename _Compare>
170	inline _OutputIterator
171	__merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
172	_RAIter2& __begin2, _RAIter2 __end2,
173	_OutputIterator __target, _DifferenceTp __max_length,
174	_Compare __comp)
175	{
176	_GLIBCXX_CALL(__max_length)
177
178	return __merge_advance_movc(__begin1, __end1, __begin2, __end2,
179	__target, __max_length, __comp);
180	}
181
182	/** @brief Merge routine fallback to sequential in case the
183	iterators of the two input sequences are of different type.
184	* @param __begin1 Begin iterator of first sequence.
185	* @param __end1 End iterator of first sequence.
186	* @param __begin2 Begin iterator of second sequence.
187	* @param __end2 End iterator of second sequence.
188	* @param __target Target begin iterator.
189	* @param __max_length Maximum number of elements to merge.
190	* @param __comp Comparator.
191	* @return Output end iterator. */
192	template<typename _RAIter1, typename _RAIter2,
193	typename _RAIter3, typename _Compare>
194	inline _RAIter3
195	__parallel_merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
196	_RAIter2& __begin2,
197	// different iterators, parallel implementation
198	// not available
199	_RAIter2 __end2, _RAIter3 __target, typename
200	std::iterator_traits<_RAIter1>::
201	difference_type __max_length, _Compare __comp)
202	{ return __merge_advance(__begin1, __end1, __begin2, __end2, __target,
203	__max_length, __comp); }
204
205	/** @brief Parallel merge routine being able to merge only the @c
206	* __max_length smallest elements.
207	*
208	* The @c __begin iterators are advanced accordingly, they might not
209	* reach @c __end, in contrast to the usual variant.
210	* The functionality is projected onto parallel_multiway_merge.
211	* @param __begin1 Begin iterator of first sequence.
212	* @param __end1 End iterator of first sequence.
213	* @param __begin2 Begin iterator of second sequence.
214	* @param __end2 End iterator of second sequence.
215	* @param __target Target begin iterator.
216	* @param __max_length Maximum number of elements to merge.
217	* @param __comp Comparator.
218	* @return Output end iterator.
219	*/
220	template<typename _RAIter1, typename _RAIter3,
221	typename _Compare>
222	inline _RAIter3
223	__parallel_merge_advance(_RAIter1& __begin1, _RAIter1 __end1,
224	_RAIter1& __begin2, _RAIter1 __end2,
225	_RAIter3 __target, typename
226	std::iterator_traits<_RAIter1>::
227	difference_type __max_length, _Compare __comp)
228	{
229	typedef typename
230	std::iterator_traits<_RAIter1>::value_type _ValueType;
231	typedef typename std::iterator_traits<_RAIter1>::
232	difference_type _DifferenceType1 /* == difference_type2 */;
233	typedef typename std::iterator_traits<_RAIter3>::
234	difference_type _DifferenceType3;
235	typedef typename std::pair<_RAIter1, _RAIter1>
236	_IteratorPair;
237
238	_IteratorPair __seqs[2] = { std::make_pair(__begin1, __end1),
239	std::make_pair(__begin2, __end2) };
240	_RAIter3 __target_end = parallel_multiway_merge
241	< /* __stable = / true, / __sentinels = */ false>
242	(__seqs, __seqs + 2, __target, multiway_merge_exact_splitting
243	< /* __stable = / true, _IteratorPair,
244	_Compare, _DifferenceType1>, __max_length, __comp,
245	omp_get_max_threads());
246
247	return __target_end;
248	}
249	} //namespace __gnu_parallel
250
251	#endif /* _GLIBCXX_PARALLEL_MERGE_H */