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.learning;
31
32 import org.sat4j.minisat.core.Constr;
33 import org.sat4j.minisat.core.DataStructureFactory;
34 import org.sat4j.minisat.core.IOrder;
35 import org.sat4j.minisat.core.Solver;
36
37 /**
38 * Learn clauses with a great number of active variables.
39 *
40 * @author leberre
41 */
42 public final class ActiveLearning<D extends DataStructureFactory> extends
43 LimitedLearning<D> {
44
45 private static final long serialVersionUID = 1L;
46
47 private double percent;
48
49 private IOrder order;
50
51 private int maxpercent;
52
53 public ActiveLearning() {
54 this(0.95);
55 }
56
57 public ActiveLearning(double d) {
58 this.percent = d;
59 }
60
61 public void setOrder(IOrder order) {
62 this.order = order;
63 }
64
65 @Override
66 public void setSolver(Solver<D> s) {
67 super.setSolver(s);
68 this.order = s.getOrder();
69 }
70
71 public void setActivityPercent(double d) {
72 this.percent = d;
73 }
74
75 public double getActivityPercent() {
76 return this.percent;
77 }
78
79 /*
80 * (non-Javadoc)
81 *
82 * @see
83 * org.sat4j.minisat.LimitedLearning#learningCondition(org.sat4j.minisat
84 * .Constr)
85 */
86 @Override
87 protected boolean learningCondition(Constr clause) {
88 int nbactivevars = 0;
89 for (int i = 0; i < clause.size(); i++) {
90 if (this.order.varActivity(clause.get(i)) > 1) {
91 nbactivevars++;
92 }
93 }
94 return nbactivevars > clause.size() * this.percent;
95 }
96
97 @Override
98 public String toString() {
99 return "Limit learning to clauses containing active literals (" + this.percent * 100 + "%)"; //$NON-NLS-1$
100 }
101
102 public void setLimit(int percent) {
103 this.maxpercent = percent;
104 }
105
106 public int getLimit() {
107 return this.maxpercent;
108 }
109 }