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.tools;
31
32 import org.sat4j.core.VecInt;
33 import org.sat4j.specs.ContradictionException;
34 import org.sat4j.specs.ISolver;
35 import org.sat4j.specs.IVecInt;
36 import org.sat4j.specs.TimeoutException;
37
38 /**
39 * Computes models with a minimal subset (with respect to set inclusion) of
40 * negative literals. This is done be adding a clause containing the negation of
41 * the negative literals appearing in the model found (which prevents any
42 * interpretation containing that subset of negative literals to be a model of
43 * the formula).
44 *
45 * Computes only one model minimal for inclusion, since there is currently no
46 * way to save the state of the solver.
47 *
48 * @author leberre
49 *
50 * @see org.sat4j.specs.ISolver#addClause(IVecInt)
51 */
52 public class Minimal4InclusionModel extends SolverDecorator<ISolver> {
53
54 private static final long serialVersionUID = 1L;
55
56 /**
57 * @param solver
58 */
59 public Minimal4InclusionModel(ISolver solver) {
60 super(solver);
61 }
62
63 /*
64 * (non-Javadoc)
65 *
66 * @see org.sat4j.ISolver#model()
67 */
68 @Override
69 public int[] model() {
70 int[] prevmodel = null;
71 IVecInt vec = new VecInt();
72 IVecInt cube = new VecInt();
73 // backUp();
74 try {
75 do {
76 prevmodel = super.model();
77 vec.clear();
78 cube.clear();
79 for (int q : prevmodel) {
80 if (q < 0) {
81 vec.push(-q);
82 } else {
83 cube.push(q);
84 }
85 }
86 addClause(vec);
87 } while (isSatisfiable(cube));
88 } catch (TimeoutException e) {
89 throw new IllegalStateException("Solver timed out");
90 } catch (ContradictionException e) {
91 // added trivial unsat clauses
92 }
93 // restore();
94 int[] newmodel = new int[vec.size()];
95 for (int i = 0, j = 0; i < prevmodel.length; i++) {
96 if (prevmodel[i] < 0) {
97 newmodel[j++] = prevmodel[i];
98 }
99 }
100
101 return newmodel;
102 }
103 }