libstdc++

resize_policy.hpp
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1 // -*- C++ -*-
2
3 // Copyright (C) 2005-2013 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 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
26
27 // Permission to use, copy, modify, sell, and distribute this software
28 // is hereby granted without fee, provided that the above copyright
29 // notice appears in all copies, and that both that copyright notice
30 // and this permission notice appear in supporting documentation. None
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34 // warranty.
35
36 /**
37 * @file binary_heap_/resize_policy.hpp
38 * Contains an implementation class for a binary_heap.
39 */
40
41 #ifndef PB_DS_BINARY_HEAP_RESIZE_POLICY_HPP
42 #define PB_DS_BINARY_HEAP_RESIZE_POLICY_HPP
43
44 #include <debug/debug.h>
45
46 namespace __gnu_pbds
47 {
48 namespace detail
49 {
50 /// Resize policy for binary heap.
51 template<typename _Tp>
52 class resize_policy
53 {
54 private:
55 enum
56 {
57 ratio = 8,
58 factor = 2
59 };
60
61 /// Next shrink size.
62 _Tp m_shrink_size;
63
64 /// Next grow size.
65 _Tp m_grow_size;
66
67 public:
68 typedef _Tp size_type;
69
70 static const _Tp min_size = 16;
71
72 resize_policy() : m_shrink_size(0), m_grow_size(min_size)
73 { PB_DS_ASSERT_VALID((*this)) }
74
75 resize_policy(const resize_policy& other)
76 : m_shrink_size(other.m_shrink_size), m_grow_size(other.m_grow_size)
77 { PB_DS_ASSERT_VALID((*this)) }
78
79 inline void
80 swap(resize_policy<_Tp>&);
81
82 inline bool
83 resize_needed_for_grow(size_type) const;
84
85 inline bool
86 resize_needed_for_shrink(size_type) const;
87
88 inline bool
89 grow_needed(size_type) const;
90
91 inline bool
92 shrink_needed(size_type) const;
93
94 inline size_type
95 get_new_size_for_grow() const;
96
97 inline size_type
98 get_new_size_for_shrink() const;
99
100 inline size_type
101 get_new_size_for_arbitrary(size_type) const;
102
103 inline void
104 notify_grow_resize();
105
106 inline void
107 notify_shrink_resize();
108
109 void
110 notify_arbitrary(size_type);
111
112 #ifdef _GLIBCXX_DEBUG
113 void
114 assert_valid(const char*, int) const;
115 #endif
116
117 #ifdef PB_DS_BINARY_HEAP_TRACE_
118 void
119 trace() const;
120 #endif
121 };
122
123 template<typename _Tp>
124 const _Tp resize_policy<_Tp>::min_size;
125
126 template<typename _Tp>
127 inline void
128 resize_policy<_Tp>::
129 swap(resize_policy<_Tp>& other)
130 {
131 std::swap(m_shrink_size, other.m_shrink_size);
132 std::swap(m_grow_size, other.m_grow_size);
133 }
134
135 template<typename _Tp>
136 inline bool
137 resize_policy<_Tp>::
138 resize_needed_for_grow(size_type size) const
139 {
140 _GLIBCXX_DEBUG_ASSERT(size <= m_grow_size);
141 return size == m_grow_size;
142 }
143
144 template<typename _Tp>
145 inline bool
146 resize_policy<_Tp>::
147 resize_needed_for_shrink(size_type size) const
148 {
149 _GLIBCXX_DEBUG_ASSERT(size <= m_grow_size);
150 return size == m_shrink_size;
151 }
152
153 template<typename _Tp>
154 inline typename resize_policy<_Tp>::size_type
155 resize_policy<_Tp>::
156 get_new_size_for_grow() const
157 { return m_grow_size * factor; }
158
159 template<typename _Tp>
160 inline typename resize_policy<_Tp>::size_type
161 resize_policy<_Tp>::
162 get_new_size_for_shrink() const
163 {
164 const size_type half_size = m_grow_size / factor;
165 return std::max(min_size, half_size);
166 }
167
168 template<typename _Tp>
169 inline typename resize_policy<_Tp>::size_type
170 resize_policy<_Tp>::
171 get_new_size_for_arbitrary(size_type size) const
172 {
173 size_type ret = min_size;
174 while (ret < size)
175 ret *= factor;
176 return ret;
177 }
178
179 template<typename _Tp>
180 inline void
181 resize_policy<_Tp>::
182 notify_grow_resize()
183 {
184 PB_DS_ASSERT_VALID((*this))
185 _GLIBCXX_DEBUG_ASSERT(m_grow_size >= min_size);
186 m_grow_size *= factor;
187 m_shrink_size = m_grow_size / ratio;
188 PB_DS_ASSERT_VALID((*this))
189 }
190
191 template<typename _Tp>
192 inline void
193 resize_policy<_Tp>::
194 notify_shrink_resize()
195 {
196 PB_DS_ASSERT_VALID((*this))
197 m_shrink_size /= factor;
198 if (m_shrink_size == 1)
199 m_shrink_size = 0;
200 m_grow_size = std::max(m_grow_size / factor, min_size);
201 PB_DS_ASSERT_VALID((*this))
202 }
203
204 template<typename _Tp>
205 inline void
206 resize_policy<_Tp>::
207 notify_arbitrary(size_type actual_size)
208 {
209 m_grow_size = actual_size;
210 m_shrink_size = m_grow_size / ratio;
211 PB_DS_ASSERT_VALID((*this))
212 }
213
214 #ifdef _GLIBCXX_DEBUG
215 template<typename _Tp>
216 void
217 resize_policy<_Tp>::
218 assert_valid(const char* __file, int __line) const
219 {
220 PB_DS_DEBUG_VERIFY(m_shrink_size == 0
221 || m_shrink_size * ratio == m_grow_size);
222 PB_DS_DEBUG_VERIFY(m_grow_size >= min_size);
223 }
224 #endif
225
226 #ifdef PB_DS_BINARY_HEAP_TRACE_
227 template<typename _Tp>
228 void
229 resize_policy<_Tp>::
230 trace() const
231 {
232 std::cerr << "shrink = " << m_shrink_size
233 << " grow = " << m_grow_size << std::endl;
234 }
235 #endif
236
237 } // namespace detail
238 } // namespace __gnu_pbds
239
240 #endif