1/*
2 Copyright (c) 2005-2019 Intel Corporation
3
4 Licensed under the Apache License, Version 2.0 (the "License");
5 you may not use this file except in compliance with the License.
6 You may obtain a copy of the License at
7
8 http://www.apache.org/licenses/LICENSE-2.0
9
10 Unless required by applicable law or agreed to in writing, software
11 distributed under the License is distributed on an "AS IS" BASIS,
12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 See the License for the specific language governing permissions and
14 limitations under the License.
15*/
16
17#ifndef __TBB_parallel_sort_H
18#define __TBB_parallel_sort_H
19
20#include "parallel_for.h"
21#include "blocked_range.h"
22#include "internal/_range_iterator.h"
23#include <algorithm>
24#include <iterator>
25#include <functional>
26#if __TBB_TASK_GROUP_CONTEXT
27 #include "tbb_profiling.h"
28#endif
29
30namespace tbb {
31
32namespace interface9 {
33//! @cond INTERNAL
34namespace internal {
35
36using tbb::internal::no_assign;
37
38//! Range used in quicksort to split elements into subranges based on a value.
39/** The split operation selects a splitter and places all elements less than or equal
40 to the value in the first range and the remaining elements in the second range.
41 @ingroup algorithms */
42template<typename RandomAccessIterator, typename Compare>
43class quick_sort_range: private no_assign {
44
45 inline size_t median_of_three(const RandomAccessIterator &array, size_t l, size_t m, size_t r) const {
46 return comp(array[l], array[m]) ? ( comp(array[m], array[r]) ? m : ( comp( array[l], array[r]) ? r : l ) )
47 : ( comp(array[r], array[m]) ? m : ( comp( array[r], array[l] ) ? r : l ) );
48 }
49
50 inline size_t pseudo_median_of_nine( const RandomAccessIterator &array, const quick_sort_range &range ) const {
51 size_t offset = range.size/8u;
52 return median_of_three(array,
53 median_of_three(array, 0, offset, offset*2),
54 median_of_three(array, offset*3, offset*4, offset*5),
55 median_of_three(array, offset*6, offset*7, range.size - 1) );
56
57 }
58
59 size_t split_range( quick_sort_range& range ) {
60 using std::iter_swap;
61 RandomAccessIterator array = range.begin;
62 RandomAccessIterator key0 = range.begin;
63 size_t m = pseudo_median_of_nine(array, range);
64 if (m) iter_swap ( array, array+m );
65
66 size_t i=0;
67 size_t j=range.size;
68 // Partition interval [i+1,j-1] with key *key0.
69 for(;;) {
70 __TBB_ASSERT( i<j, NULL );
71 // Loop must terminate since array[l]==*key0.
72 do {
73 --j;
74 __TBB_ASSERT( i<=j, "bad ordering relation?" );
75 } while( comp( *key0, array[j] ));
76 do {
77 __TBB_ASSERT( i<=j, NULL );
78 if( i==j ) goto partition;
79 ++i;
80 } while( comp( array[i],*key0 ));
81 if( i==j ) goto partition;
82 iter_swap( array+i, array+j );
83 }
84partition:
85 // Put the partition key were it belongs
86 iter_swap( array+j, key0 );
87 // array[l..j) is less or equal to key.
88 // array(j..r) is greater or equal to key.
89 // array[j] is equal to key
90 i=j+1;
91 size_t new_range_size = range.size-i;
92 range.size = j;
93 return new_range_size;
94 }
95
96public:
97
98 static const size_t grainsize = 500;
99 const Compare &comp;
100 size_t size;
101 RandomAccessIterator begin;
102
103 quick_sort_range( RandomAccessIterator begin_, size_t size_, const Compare &comp_ ) :
104 comp(comp_), size(size_), begin(begin_) {}
105
106 bool empty() const {return size==0;}
107 bool is_divisible() const {return size>=grainsize;}
108
109 quick_sort_range( quick_sort_range& range, split )
110 : comp(range.comp)
111 , size(split_range(range))
112 // +1 accounts for the pivot element, which is at its correct place
113 // already and, therefore, is not included into subranges.
114 , begin(range.begin+range.size+1) {}
115};
116
117#if __TBB_TASK_GROUP_CONTEXT
118//! Body class used to test if elements in a range are presorted
119/** @ingroup algorithms */
120template<typename RandomAccessIterator, typename Compare>
121class quick_sort_pretest_body : no_assign {
122 const Compare &comp;
123
124public:
125 quick_sort_pretest_body(const Compare &_comp) : comp(_comp) {}
126
127 void operator()( const blocked_range<RandomAccessIterator>& range ) const {
128 task &my_task = task::self();
129 RandomAccessIterator my_end = range.end();
130
131 int i = 0;
132 for (RandomAccessIterator k = range.begin(); k != my_end; ++k, ++i) {
133 if ( i%64 == 0 && my_task.is_cancelled() ) break;
134
135 // The k-1 is never out-of-range because the first chunk starts at begin+serial_cutoff+1
136 if ( comp( *(k), *(k-1) ) ) {
137 my_task.cancel_group_execution();
138 break;
139 }
140 }
141 }
142
143};
144#endif /* __TBB_TASK_GROUP_CONTEXT */
145
146//! Body class used to sort elements in a range that is smaller than the grainsize.
147/** @ingroup algorithms */
148template<typename RandomAccessIterator, typename Compare>
149struct quick_sort_body {
150 void operator()( const quick_sort_range<RandomAccessIterator,Compare>& range ) const {
151 //SerialQuickSort( range.begin, range.size, range.comp );
152 std::sort( range.begin, range.begin + range.size, range.comp );
153 }
154};
155
156//! Wrapper method to initiate the sort by calling parallel_for.
157/** @ingroup algorithms */
158template<typename RandomAccessIterator, typename Compare>
159void parallel_quick_sort( RandomAccessIterator begin, RandomAccessIterator end, const Compare& comp ) {
160#if __TBB_TASK_GROUP_CONTEXT
161 task_group_context my_context(PARALLEL_SORT);
162 const int serial_cutoff = 9;
163
164 __TBB_ASSERT( begin + serial_cutoff < end, "min_parallel_size is smaller than serial cutoff?" );
165 RandomAccessIterator k = begin;
166 for ( ; k != begin + serial_cutoff; ++k ) {
167 if ( comp( *(k+1), *k ) ) {
168 goto do_parallel_quick_sort;
169 }
170 }
171
172 parallel_for( blocked_range<RandomAccessIterator>(k+1, end),
173 quick_sort_pretest_body<RandomAccessIterator,Compare>(comp),
174 auto_partitioner(),
175 my_context);
176
177 if (my_context.is_group_execution_cancelled())
178do_parallel_quick_sort:
179#endif /* __TBB_TASK_GROUP_CONTEXT */
180 parallel_for( quick_sort_range<RandomAccessIterator,Compare>(begin, end-begin, comp ),
181 quick_sort_body<RandomAccessIterator,Compare>(),
182 auto_partitioner() );
183}
184
185} // namespace internal
186//! @endcond
187} // namespace interfaceX
188
189/** \page parallel_sort_iter_req Requirements on iterators for parallel_sort
190 Requirements on the iterator type \c It and its value type \c T for \c parallel_sort:
191
192 - \code void iter_swap( It a, It b ) \endcode Swaps the values of the elements the given
193 iterators \c a and \c b are pointing to. \c It should be a random access iterator.
194
195 - \code bool Compare::operator()( const T& x, const T& y ) \endcode True if x comes before y;
196**/
197
198/** \name parallel_sort
199 See also requirements on \ref parallel_sort_iter_req "iterators for parallel_sort". **/
200//@{
201
202//! Sorts the data in [begin,end) using the given comparator
203/** The compare function object is used for all comparisons between elements during sorting.
204 The compare object must define a bool operator() function.
205 @ingroup algorithms **/
206template<typename RandomAccessIterator, typename Compare>
207void parallel_sort( RandomAccessIterator begin, RandomAccessIterator end, const Compare& comp) {
208 const int min_parallel_size = 500;
209 if( end > begin ) {
210 if (end - begin < min_parallel_size) {
211 std::sort(begin, end, comp);
212 } else {
213 interface9::internal::parallel_quick_sort(begin, end, comp);
214 }
215 }
216}
217
218//! Sorts the data in [begin,end) with a default comparator \c std::less<RandomAccessIterator>
219/** @ingroup algorithms **/
220template<typename RandomAccessIterator>
221inline void parallel_sort( RandomAccessIterator begin, RandomAccessIterator end ) {
222 parallel_sort( begin, end, std::less< typename std::iterator_traits<RandomAccessIterator>::value_type >() );
223}
224
225//! Sorts the data in rng using the given comparator
226/** @ingroup algorithms **/
227template<typename Range, typename Compare>
228void parallel_sort(Range& rng, const Compare& comp) {
229 parallel_sort(tbb::internal::first(rng), tbb::internal::last(rng), comp);
230}
231
232//! Sorts the data in rng with a default comparator \c std::less<RandomAccessIterator>
233/** @ingroup algorithms **/
234template<typename Range>
235void parallel_sort(Range& rng) {
236 parallel_sort(tbb::internal::first(rng), tbb::internal::last(rng));
237}
238
239//! Sorts the data in the range \c [begin,end) with a default comparator \c std::less<T>
240/** @ingroup algorithms **/
241template<typename T>
242inline void parallel_sort( T * begin, T * end ) {
243 parallel_sort( begin, end, std::less< T >() );
244}
245//@}
246
247
248} // namespace tbb
249
250#endif
251
252