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.tools;
27
28 import org.sat4j.core.VecInt;
29 import org.sat4j.specs.ContradictionException;
30 import org.sat4j.specs.ISolver;
31 import org.sat4j.specs.IVecInt;
32 import org.sat4j.specs.TimeoutException;
33
34 /**
35 * Computes models with a minimal number (with respect to cardinality) of
36 * negative literals. This is done be adding a constraint on the number of
37 * negative literals each time a model if found (the number of negative literals
38 * occuring in the model minus one).
39 *
40 * @author leberre
41 * @see org.sat4j.specs.ISolver#addAtMost(IVecInt, int)
42 */
43 public class Minimal4CardinalityModel extends SolverDecorator {
44
45 private static final long serialVersionUID = 1L;
46
47 /**
48 * @param solver
49 */
50 public Minimal4CardinalityModel(ISolver solver) {
51 super(solver);
52 }
53
54 /*
55 * (non-Javadoc)
56 *
57 * @see org.sat4j.ISolver#model()
58 */
59 @Override
60 public int[] model() {
61 int[] prevmodel = null;
62 IVecInt vec = new VecInt();
63 // backUp();
64 try {
65 do {
66 prevmodel = super.model();
67 vec.clear();
68 for (int i = 1; i <= nVars(); i++) {
69 vec.push(-i);
70 }
71 int counter = 0;
72 for (int q : prevmodel) {
73 if (q < 0) {
74 counter++;
75 }
76 }
77 addAtMost(vec, counter - 1);
78 System.err.println(counter);
79 } while (isSatisfiable());
80 } catch (TimeoutException e) {
81 System.err.println("Solver timed out"); //$NON-NLS-1$
82 } catch (ContradictionException e) {
83 System.err.println("added trivial unsat clauses?" + vec); //$NON-NLS-1$
84 }
85 // restore();
86 return prevmodel;
87 }
88 }