1 /*
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2006 Daniel Le Berre
3 *
4 * Based on the original minisat specification from:
5 *
6 * An extensible SAT solver. Niklas E?n and Niklas S?rensson. Proceedings of the
7 * Sixth International Conference on Theory and Applications of Satisfiability
8 * Testing, LNCS 2919, pp 502-518, 2003.
9 *
10 * This library is free software; you can redistribute it and/or modify it under
11 * the terms of the GNU Lesser General Public License as published by the Free
12 * Software Foundation; either version 2.1 of the License, or (at your option)
13 * any later version.
14 *
15 * This library is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
18 * details.
19 *
20 * You should have received a copy of the GNU Lesser General Public License
21 * along with this library; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 *
24 */
25
26 package org.sat4j.minisat.learning;
27
28 import org.sat4j.minisat.core.Constr;
29 import org.sat4j.minisat.core.ILits;
30 import org.sat4j.minisat.core.IOrder;
31 import org.sat4j.minisat.core.Solver;
32
33 /**
34 * Learn clauses with a great number of active variables.
35 *
36 * @author leberre
37 */
38 public class ActiveLearning<L extends ILits> extends LimitedLearning<L> {
39
40 private static final long serialVersionUID = 1L;
41
42 private double percent;
43
44 private IOrder<L> order;
45
46 private int maxpercent;
47
48 public ActiveLearning() {
49 this(0.95);
50 }
51
52 public ActiveLearning(double d) {
53 this.percent = d;
54 }
55
56 public void setOrder(IOrder<L> order) {
57 this.order = order;
58 }
59
60 @Override
61 public void setSolver(Solver<L> s) {
62 super.setSolver(s);
63 this.order = s.getOrder();
64 }
65
66 public void setActivityPercent(double d) {
67 percent = d;
68 }
69
70 public double getActivityPercent() {
71 return percent;
72 }
73
74 /*
75 * (non-Javadoc)
76 *
77 * @see org.sat4j.minisat.LimitedLearning#learningCondition(org.sat4j.minisat.Constr)
78 */
79 @Override
80 protected boolean learningCondition(Constr clause) {
81 int nbactivevars = 0;
82 for (int i = 0; i < clause.size(); i++) {
83 if (order.varActivity(clause.get(i)) > 1) {
84 nbactivevars++;
85 }
86 }
87 return nbactivevars > clause.size() * percent;
88 }
89
90 @Override
91 public String toString() {
92 return "Limit learning to clauses containing active literals ("+percent*100+"%)"; //$NON-NLS-1$
93 }
94
95 public void setLimit(int percent) {
96 maxpercent = percent;
97 }
98
99 public int getLimit() {
100 return maxpercent;
101 }
102 }