1 /*******************************************************************************
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004, 2012 Artois University and CNRS
3 *
4 * All rights reserved. This program and the accompanying materials
5 * are made available under the terms of the Eclipse Public License v1.0
6 * which accompanies this distribution, and is available at
7 * http://www.eclipse.org/legal/epl-v10.html
8 *
9 * Alternatively, the contents of this file may be used under the terms of
10 * either the GNU Lesser General Public License Version 2.1 or later (the
11 * "LGPL"), in which case the provisions of the LGPL are applicable instead
12 * of those above. If you wish to allow use of your version of this file only
13 * under the terms of the LGPL, and not to allow others to use your version of
14 * this file under the terms of the EPL, indicate your decision by deleting
15 * the provisions above and replace them with the notice and other provisions
16 * required by the LGPL. If you do not delete the provisions above, a recipient
17 * may use your version of this file under the terms of the EPL or the LGPL.
18 *
19 * Based on the original MiniSat specification from:
20 *
21 * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
22 * Sixth International Conference on Theory and Applications of Satisfiability
23 * Testing, LNCS 2919, pp 502-518, 2003.
24 *
25 * See www.minisat.se for the original solver in C++.
26 *
27 * Contributors:
28 * CRIL - initial API and implementation
29 *******************************************************************************/
30 package org.sat4j.minisat.restarts;
31
32 import org.sat4j.minisat.core.CircularBuffer;
33 import org.sat4j.minisat.core.Constr;
34 import org.sat4j.minisat.core.RestartStrategy;
35 import org.sat4j.minisat.core.SearchParams;
36 import org.sat4j.minisat.core.SolverStats;
37
38 /**
39 * Dynamic restart strategy of Glucose 2.1 as presented in Refining restarts
40 * strategies for SAT and UNSAT formulae. Gilles Audemard and Laurent Simon, in
41 * CP'2012.
42 *
43 * @author leberre
44 *
45 */
46 public class Glucose21Restarts implements RestartStrategy {
47
48 /**
49 *
50 */
51 private static final long serialVersionUID = 1L;
52
53 private final CircularBuffer bufferLBD = new CircularBuffer(50);
54
55 private final CircularBuffer bufferTrail = new CircularBuffer(5000);
56
57 private long sumOfAllLBD = 0;
58
59 private SolverStats stats;
60
61 public void reset() {
62 sumOfAllLBD = 0;
63 bufferLBD.clear();
64 bufferTrail.clear();
65 }
66
67 public void newConflict() {
68
69 }
70
71 public void newLearnedClause(Constr learned, int trailLevel) {
72 // on conflict
73 int lbd = (int) learned.getActivity();
74 bufferLBD.push(lbd);
75 sumOfAllLBD += lbd;
76 bufferTrail.push(trailLevel);
77 // was
78 // ... trailLevel > 1.4 * bufferTrail.average()
79 // uses now only integers to avoid rounding issues
80 if (stats.conflicts > 10000 && bufferTrail.isFull()
81 && trailLevel * 5L > 7L * bufferTrail.average()) {
82 bufferLBD.clear();
83 }
84 }
85
86 public void init(SearchParams params, SolverStats stats) {
87 this.stats = stats;
88 reset();
89 }
90
91 public long nextRestartNumberOfConflict() {
92 return 0;
93 }
94
95 public boolean shouldRestart() {
96 // was
97 // ... && bufferLBD.average() * 0.8 > sumOfAllLBD / stats.conflicts
98 // uses now only integers to avoid rounding issues
99 return bufferLBD.isFull()
100 && bufferLBD.average() * stats.conflicts * 4L > sumOfAllLBD * 5L;
101 }
102
103 public void onRestart() {
104 bufferLBD.clear();
105 }
106
107 public void onBackjumpToRootLevel() {
108 }
109
110 @Override
111 public String toString() {
112 return "Glucose 2.1 dynamic restart strategy";
113 }
114 }