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.opt;
29
30 import org.sat4j.core.VecInt;
31 import org.sat4j.specs.ContradictionException;
32 import org.sat4j.specs.IOptimizationProblem;
33 import org.sat4j.specs.ISolver;
34 import org.sat4j.specs.IVecInt;
35 import org.sat4j.specs.TimeoutException;
36 import org.sat4j.tools.SolverDecorator;
37
38 /**
39 * Computes a solution with the smallest number of satisfied literals.
40 *
41 * Please make sure that newVar(howmany) is called first to setup the decorator.
42 *
43 * @author leberre
44 */
45 public class MinOneDecorator extends SolverDecorator<ISolver> implements
46 IOptimizationProblem {
47
48 /**
49 *
50 */
51 private static final long serialVersionUID = 1L;
52
53 private int[] prevmodel;
54
55 public MinOneDecorator(ISolver solver) {
56 super(solver);
57 }
58
59 public boolean admitABetterSolution() throws TimeoutException {
60 boolean result = isSatisfiable(true);
61 if (result) {
62 prevmodel = super.model();
63 }
64 return result;
65 }
66
67 public boolean hasNoObjectiveFunction() {
68 return false;
69 }
70
71 public boolean nonOptimalMeansSatisfiable() {
72 return true;
73 }
74
75 private int counter;
76
77 public Number calculateObjective() {
78 counter = 0;
79 for (int p : prevmodel) {
80 if (p > 0) {
81 counter++;
82 }
83 }
84 return new Integer(counter);
85 }
86
87 private final IVecInt literals = new VecInt();
88
89 public void discard() throws ContradictionException {
90 if (literals.isEmpty()) {
91 for (int i = 1; i <= nVars(); i++) {
92 literals.push(i);
93 }
94 }
95 addAtMost(literals, counter - 1);
96 }
97
98 @Override
99 public int[] model() {
100 // DLB findbugs ok
101 return prevmodel;
102 }
103
104 @Override
105 public void reset() {
106 literals.clear();
107 super.reset();
108 }
109
110 }