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stable_sort.hpp
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1
2// Range v3 library
3//
4// Copyright Eric Niebler 2013-present
5//
6// Use, modification and distribution is subject to the
7// Boost Software License, Version 1.0. (See accompanying
8// file LICENSE_1_0.txt or copy at
9// http://www.boost.org/LICENSE_1_0.txt)
10//
11// Project home: https://github.com/ericniebler/range-v3
12//
13// Copyright (c) 1994
14// Hewlett-Packard Company
15//
16// Permission to use, copy, modify, distribute and sell this software
17// and its documentation for any purpose is hereby granted without fee,
18// provided that the above copyright notice appear in all copies and
19// that both that copyright notice and this permission notice appear
20// in supporting documentation. Hewlett-Packard Company makes no
21// representations about the suitability of this software for any
22// purpose. It is provided "as is" without express or implied warranty.
23//
24// Copyright (c) 1996
25// Silicon Graphics Computer Systems, Inc.
26//
27// Permission to use, copy, modify, distribute and sell this software
28// and its documentation for any purpose is hereby granted without fee,
29// provided that the above copyright notice appear in all copies and
30// that both that copyright notice and this permission notice appear
31// in supporting documentation. Silicon Graphics makes no
32// representations about the suitability of this software for any
33// purpose. It is provided "as is" without express or implied warranty.
34//
35
36#ifndef RANGES_V3_ALGORITHM_STABLE_SORT_HPP
37#define RANGES_V3_ALGORITHM_STABLE_SORT_HPP
38
39#include <functional>
40#include <iterator>
41#include <memory>
42
44
60#include <range/v3/utility/static_const.hpp>
61
62#include <range/v3/detail/prologue.hpp>
63
64namespace ranges
65{
68
70 namespace detail
71 {
72 template<typename I, typename C, typename P>
73 void inplace_stable_sort(I first, I last, C & pred, P & proj)
74 {
75 if(last - first < 15)
76 return detail::insertion_sort(first, last, pred, proj), void();
77 I middle = first + (last - first) / 2;
78 detail::inplace_stable_sort(first, middle, pred, proj);
79 detail::inplace_stable_sort(middle, last, pred, proj);
80 detail::inplace_merge_no_buffer(first,
81 middle,
82 last,
83 middle - first,
84 last - middle,
85 std::ref(pred),
86 std::ref(proj));
87 }
88
89 template<typename I1, typename I2, typename D, typename C, typename P>
90 void merge_sort_loop(I1 first, I1 last, I2 result, D step_size, C & pred,
91 P & proj)
92 {
93 D two_step = 2 * step_size;
94 while(last - first >= two_step)
95 {
96 result = merge(make_move_iterator(first),
97 make_move_iterator(first + step_size),
98 make_move_iterator(first + step_size),
99 make_move_iterator(first + two_step),
100 result,
101 std::ref(pred),
102 std::ref(proj),
103 std::ref(proj))
104 .out;
105 first += two_step;
106 }
107 step_size = ranges::min(D(last - first), step_size);
108 merge(make_move_iterator(first),
109 make_move_iterator(first + step_size),
110 make_move_iterator(first + step_size),
111 make_move_iterator(last),
112 result,
113 std::ref(pred),
114 std::ref(proj),
115 std::ref(proj));
116 }
117
118 constexpr int merge_sort_chunk_size()
119 {
120 return 7;
121 }
122
123 template<typename I, typename D, typename C, typename P>
124 void chunk_insertion_sort(I first, I last, D chunk_size, C & pred, P & proj)
125 {
126 while(last - first >= chunk_size)
127 {
128 detail::insertion_sort(first, first + chunk_size, pred, proj);
129 first += chunk_size;
130 }
131 detail::insertion_sort(first, last, pred, proj);
132 }
133
134 // buffer points to raw memory, we create objects, and then restore the buffer to
135 // raw memory by destroying the objects on return.
136 template<typename I, typename V, typename C, typename P>
137 void merge_sort_with_buffer(I first, I last, V * buffer, C & pred, P & proj)
138 {
139 iter_difference_t<I> len = last - first,
140 step_size = detail::merge_sort_chunk_size();
141 detail::chunk_insertion_sort(first, last, step_size, pred, proj);
142 if(step_size >= len)
143 return;
144 // The first call to merge_sort_loop moves into raw storage. Construct
145 // on-demand and keep track of how many objects we need to destroy.
146 V * buffer_end = buffer + static_cast<std::ptrdiff_t>(len);
147 auto tmpbuf = make_raw_buffer(buffer);
148 detail::merge_sort_loop(first, last, tmpbuf.begin(), step_size, pred, proj);
149 step_size *= 2;
150 loop:
151 detail::merge_sort_loop(
152 buffer, buffer_end, first, (std::ptrdiff_t)step_size, pred, proj);
153 step_size *= 2;
154 if(step_size >= len)
155 return;
156 detail::merge_sort_loop(first, last, buffer, step_size, pred, proj);
157 step_size *= 2;
158 goto loop;
159 }
160
161 // buffer points to raw memory
162 template<typename I, typename V, typename C, typename P>
163 void stable_sort_adaptive(I first, I last, V * buffer, std::ptrdiff_t buffer_size,
164 C & pred, P & proj)
165 {
166 iter_difference_t<I> len = (last - first + 1) / 2;
167 I middle = first + len;
168 if(len > buffer_size)
169 {
170 detail::stable_sort_adaptive(
171 first, middle, buffer, buffer_size, pred, proj);
172 detail::stable_sort_adaptive(
173 middle, last, buffer, buffer_size, pred, proj);
174 }
175 else
176 {
177 detail::merge_sort_with_buffer(first, middle, buffer, pred, proj);
178 detail::merge_sort_with_buffer(middle, last, buffer, pred, proj);
179 }
180 detail::merge_adaptive(first,
181 middle,
182 last,
183 middle - first,
184 last - middle,
185 buffer,
186 buffer_size,
187 std::ref(pred),
188 std::ref(proj));
189 }
190 } // namespace detail
192
193 RANGES_FUNC_BEGIN(stable_sort)
194
195
196 template(typename I, typename S, typename C = less, typename P = identity)(
197 requires sortable<I, C, P> AND random_access_iterator<I> AND
198 sentinel_for<S, I>)
199 I RANGES_FUNC(stable_sort)(I first, S end_, C pred = C{}, P proj = P{})
200 {
201 I last = ranges::next(first, end_);
202 using D = iter_difference_t<I>;
203 using V = iter_value_t<I>;
204 D len = last - first;
205 auto buf =
206 len > 256 ? detail::get_temporary_buffer<V>(len) : detail::value_init{};
207 std::unique_ptr<V, detail::return_temporary_buffer> h{buf.first};
208 if(buf.first == nullptr)
209 detail::inplace_stable_sort(first, last, pred, proj);
210 else
211 detail::stable_sort_adaptive(
212 first, last, buf.first, buf.second, pred, proj);
213 return last;
214 }
215
217 template(typename Rng, typename C = less, typename P = identity)(
218 requires sortable<iterator_t<Rng>, C, P> AND random_access_range<Rng>)
219 borrowed_iterator_t<Rng> //
220 RANGES_FUNC(stable_sort)(Rng && rng, C pred = C{}, P proj = P{}) //
221 {
222 return (*this)(begin(rng), end(rng), std::move(pred), std::move(proj));
223 }
224
225 RANGES_FUNC_END(stable_sort)
226
227 namespace cpp20
228 {
229 using ranges::stable_sort;
230 }
232} // namespace ranges
233
234#include <range/v3/detail/epilogue.hpp>
235
236#endif
front< Pair > first
Retrieve the first element of the pair Pair.
Definition meta.hpp:2251
bool_<(T::type::value< U::type::value)> less
A Boolean integral constant wrapper around true if T::type::value is less than U::type::value; false,...
Definition meta.hpp:255