1 /*******************************************************************************
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
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 *******************************************************************************/
28 package org.sat4j.minisat.learning;
29
30 import org.sat4j.minisat.core.Constr;
31 import org.sat4j.minisat.core.DataStructureFactory;
32 import org.sat4j.minisat.core.IOrder;
33 import org.sat4j.minisat.core.Solver;
34
35 /**
36 * Learn clauses with a great number of active variables.
37 *
38 * @author leberre
39 */
40 public class ActiveLearning<D extends DataStructureFactory> extends LimitedLearning<D> {
41
42 private static final long serialVersionUID = 1L;
43
44 private double percent;
45
46 private IOrder order;
47
48 private int maxpercent;
49
50 public ActiveLearning() {
51 this(0.95);
52 }
53
54 public ActiveLearning(double d) {
55 this.percent = d;
56 }
57
58 public void setOrder(IOrder order) {
59 this.order = order;
60 }
61
62 @Override
63 public void setSolver(Solver<D> s) {
64 super.setSolver(s);
65 this.order = s.getOrder();
66 }
67
68 public void setActivityPercent(double d) {
69 percent = d;
70 }
71
72 public double getActivityPercent() {
73 return percent;
74 }
75
76 /*
77 * (non-Javadoc)
78 *
79 * @see org.sat4j.minisat.LimitedLearning#learningCondition(org.sat4j.minisat.Constr)
80 */
81 @Override
82 protected boolean learningCondition(Constr clause) {
83 int nbactivevars = 0;
84 for (int i = 0; i < clause.size(); i++) {
85 if (order.varActivity(clause.get(i)) > 1) {
86 nbactivevars++;
87 }
88 }
89 return nbactivevars > clause.size() * percent;
90 }
91
92 @Override
93 public String toString() {
94 return "Limit learning to clauses containing active literals ("+percent*100+"%)"; //$NON-NLS-1$
95 }
96
97 public void setLimit(int percent) {
98 maxpercent = percent;
99 }
100
101 public int getLimit() {
102 return maxpercent;
103 }
104 }