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.opt;
27
28 import java.math.BigInteger;
29
30 import org.sat4j.specs.ContradictionException;
31 import org.sat4j.specs.IOptimizationProblem;
32 import org.sat4j.specs.ISolver;
33 import org.sat4j.specs.TimeoutException;
34 import org.sat4j.tools.SolverDecorator;
35
36 /**
37 * A decorator that computes minimal pseudo boolean models.
38 *
39 * @author daniel
40 *
41 */
42 public class PseudoOptDecorator extends SolverDecorator implements
43 IOptimizationProblem {
44
45 /**
46 *
47 */
48 private static final long serialVersionUID = 1L;
49
50 private ObjectiveFunction objfct;
51
52 private int[] prevmodel;
53
54 public PseudoOptDecorator(ISolver solver) {
55 super(solver);
56 }
57
58 public void setObjectTiveFunction(ObjectiveFunction objf) {
59 objfct = objf;
60 }
61
62 public boolean admitABetterSolution() throws TimeoutException {
63 boolean result = super.isSatisfiable();
64 if (result)
65 prevmodel = super.model();
66 return result;
67 }
68
69 public boolean hasNoObjectiveFunction() {
70 return objfct == null;
71 }
72
73 public boolean nonOptimalMeansSatisfiable() {
74 return true;
75 }
76
77 public Number calculateObjective() {
78 return objfct.calculateDegree(prevmodel);
79 }
80
81 public void discard() throws ContradictionException {
82 super.addPseudoBoolean(objfct.getVars(), objfct.getCoeffs(), false,
83 objfct.calculateDegree(prevmodel).subtract(BigInteger.ONE));
84 }
85
86 @Override
87 public int[] model() {
88 // DLB findbugs ok
89 return prevmodel;
90 }
91
92 }