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.ILits;
33 import org.sat4j.minisat.core.IOrder;
34 import org.sat4j.minisat.core.Solver;
35
36 /**
37 * Learn clauses with a great number of active variables.
38 *
39 * @author leberre
40 */
41 public class ActiveLearning<L extends ILits,D extends DataStructureFactory<L>> extends LimitedLearning<L,D> {
42
43 private static final long serialVersionUID = 1L;
44
45 private double percent;
46
47 private IOrder<L> order;
48
49 private int maxpercent;
50
51 public ActiveLearning() {
52 this(0.95);
53 }
54
55 public ActiveLearning(double d) {
56 this.percent = d;
57 }
58
59 public void setOrder(IOrder<L> order) {
60 this.order = order;
61 }
62
63 @Override
64 public void setSolver(Solver<L,D> s) {
65 super.setSolver(s);
66 this.order = s.getOrder();
67 }
68
69 public void setActivityPercent(double d) {
70 percent = d;
71 }
72
73 public double getActivityPercent() {
74 return percent;
75 }
76
77 /*
78 * (non-Javadoc)
79 *
80 * @see org.sat4j.minisat.LimitedLearning#learningCondition(org.sat4j.minisat.Constr)
81 */
82 @Override
83 protected boolean learningCondition(Constr clause) {
84 int nbactivevars = 0;
85 for (int i = 0; i < clause.size(); i++) {
86 if (order.varActivity(clause.get(i)) > 1) {
87 nbactivevars++;
88 }
89 }
90 return nbactivevars > clause.size() * percent;
91 }
92
93 @Override
94 public String toString() {
95 return "Limit learning to clauses containing active literals ("+percent*100+"%)"; //$NON-NLS-1$
96 }
97
98 public void setLimit(int percent) {
99 maxpercent = percent;
100 }
101
102 public int getLimit() {
103 return maxpercent;
104 }
105 }