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dekker.one
1/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
2/*
3 * Main authors:
4 * Christian Schulte <schulte@gecode.org>
5 *
6 * Copyright:
7 * Christian Schulte, 2009
8 *
9 * This file is part of Gecode, the generic constraint
10 * development environment:
11 * http://www.gecode.org
12 *
13 * Permission is hereby granted, free of charge, to any person obtaining
14 * a copy of this software and associated documentation files (the
15 * "Software"), to deal in the Software without restriction, including
16 * without limitation the rights to use, copy, modify, merge, publish,
17 * distribute, sublicense, and/or sell copies of the Software, and to
18 * permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be
22 * included in all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
28 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
29 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
30 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 *
32 */
33
34#include <cmath>
35
36namespace Gecode { namespace Kernel {
37
38 /// Global propagator information
39 class GPI {
40 public:
41 /// Class for storing propagator information
42 class Info {
43 public:
44 /// Propagator identifier
45 unsigned int pid;
46 /// Group identifier
47 unsigned int gid;
48 /// The afc value
49 double afc;
50 /// Initialize
51 void init(unsigned int pid, unsigned int gid);
52 };
53 private:
54 /// Block of propagator information
55 class Block : public HeapAllocated {
56 public:
57 /// Number of propagator information entries in a block
58 static const int n_info = 8192;
59 /// Info entries
60 Info info[n_info];
61 /// Next block
62 Block* next;
63 /// Number of free blocks
64 int free;
65 /// Initialize
66 Block(void);
67 /// Rescale used afc values in entries
68 void rescale(void);
69 };
70 /// The current block
71 Block* b;
72 /// The inverse decay factor
73 double invd;
74 /// Next free propagator id
75 std::atomic<unsigned int> npid;
76 /// Whether to unshare
77 bool us;
78 /// The first block
79 Block fst;
80 /// Mutex to synchronize globally shared access
81 GECODE_KERNEL_EXPORT static Support::Mutex m;
82 public:
83 /// Initialize
84 GPI(void);
85 /// Set decay factor to \a d
86 void decay(double d);
87 /// Return decay factor
88 double decay(void) const;
89 /// Increment failure count
90 void fail(Info& c);
91 /// Allocate info for existing propagator with pid \a p
92 Info* allocate(unsigned int p, unsigned int gid);
93 /// Allocate new actor info
94 Info* allocate(unsigned int gid);
95 /// Return next free propagator id
96 unsigned int pid(void) const;
97 /// Provide access to unshare info and set to true
98 bool unshare(void);
99 /// Delete
100 ~GPI(void);
101 };
102
103
104 forceinline void
105 GPI::Info::init(unsigned int pid0, unsigned int gid0) {
106 pid=pid0; gid=gid0; afc=1.0;
107 }
108
109
110 forceinline
111 GPI::Block::Block(void)
112 : next(nullptr), free(n_info) {}
113
114 forceinline void
115 GPI::Block::rescale(void) {
116 for (int i=free; i < n_info; i++)
117 info[i].afc *= Kernel::Config::rescale;
118 }
119
120
121 forceinline
122 GPI::GPI(void)
123 : b(&fst), invd(1.0), npid(0U), us(false) {}
124
125 forceinline void
126 GPI::fail(Info& c) {
127 m.acquire();
128 c.afc = invd * (c.afc + 1.0);
129 if (c.afc > Kernel::Config::rescale_limit)
130 for (Block* i = b; i != nullptr; i = i->next)
131 i->rescale();
132 m.release();
133 }
134
135 forceinline double
136 GPI::decay(void) const {
137 double d;
138 const_cast<GPI&>(*this).m.acquire();
139 d = 1.0 / invd;
140 const_cast<GPI&>(*this).m.release();
141 return d;
142 }
143
144 forceinline unsigned int
145 GPI::pid(void) const {
146 return npid.load(std::memory_order_acquire);
147 }
148
149 forceinline bool
150 GPI::unshare(void) {
151 bool u;
152 m.acquire();
153 u = us; us = true;
154 m.release();
155 return u;
156 }
157
158 forceinline void
159 GPI::decay(double d) {
160 m.acquire();
161 invd = 1.0 / d;
162 m.release();
163 }
164
165 forceinline GPI::Info*
166 GPI::allocate(unsigned int p, unsigned int gid) {
167 Info* c;
168 m.acquire();
169 if (b->free == 0) {
170 Block* n = new Block;
171 n->next = b; b = n;
172 }
173 c = &b->info[--b->free];
174 m.release();
175 c->init(p,gid);
176 return c;
177 }
178
179 forceinline GPI::Info*
180 GPI::allocate(unsigned int gid) {
181 Info* c;
182 m.acquire();
183 if (b->free == 0) {
184 Block* n = new Block;
185 n->next = b; b = n;
186 }
187 c = &b->info[--b->free];
188 m.release();
189 c->init(npid.fetch_add(std::memory_order::memory_order_seq_cst),gid);
190 return c;
191 }
192
193 forceinline
194 GPI::~GPI(void) {
195 Block* n = b;
196 while (n != &fst) {
197 Block* d = n;
198 n = n->next;
199 delete d;
200 }
201 }
202
203}}
204
205// STATISTICS: kernel-prop