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 subset (with respect to set inclusion) of
36 * negative literals. This is done be adding a clause containing the negation of
37 * the negative literals appearing in the model found (which prevents any
38 * interpretation containing that subset of negative literals to be a model of
39 * the formula).
40 *
41 * Computes only one model minimal for inclusion, since there is currently no
42 * way to save the state of the solver.
43 *
44 * @author leberre
45 *
46 * @see org.sat4j.specs.ISolver#addClause(IVecInt)
47 */
48 public class Minimal4InclusionModel extends SolverDecorator {
49
50 private static final long serialVersionUID = 1L;
51
52 /**
53 * @param solver
54 */
55 public Minimal4InclusionModel(ISolver solver) {
56 super(solver);
57 }
58
59 /*
60 * (non-Javadoc)
61 *
62 * @see org.sat4j.ISolver#model()
63 */
64 @Override
65 public int[] model() {
66 int[] prevmodel = null;
67 IVecInt vec = new VecInt();
68 IVecInt cube = new VecInt();
69 // backUp();
70 try {
71 do {
72 prevmodel = super.model();
73 vec.clear();
74 cube.clear();
75 for (int q : prevmodel) {
76 if (q < 0) {
77 vec.push(-q);
78 } else {
79 cube.push(q);
80 }
81 }
82 // System.out.println("minimizing " + vec + "/" + cube);
83 addClause(vec);
84 } while (isSatisfiable(cube));
85 } catch (TimeoutException e) {
86 // System.err.println("Solver timed out");
87 } catch (ContradictionException e) {
88 // System.out.println("added trivial unsat clauses?" + vec);
89 }
90 // restore();
91 int[] newmodel = new int[vec.size()];
92 for (int i = 0, j = 0; i < prevmodel.length; i++) {
93 if (prevmodel[i] < 0) {
94 newmodel[j++] = prevmodel[i];
95 }
96 }
97
98 return newmodel;
99 }
100 }