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.tools;
29
30 import org.sat4j.core.VecInt;
31 import org.sat4j.specs.ContradictionException;
32 import org.sat4j.specs.ISolver;
33 import org.sat4j.specs.IVecInt;
34 import org.sat4j.specs.TimeoutException;
35
36 /**
37 * Computes models with a minimal subset (with respect to set inclusion) of
38 * negative literals. This is done be adding a clause containing the negation of
39 * the negative literals appearing in the model found (which prevents any
40 * interpretation containing that subset of negative literals to be a model of
41 * the formula).
42 *
43 * Computes only one model minimal for inclusion, since there is currently no
44 * way to save the state of the solver.
45 *
46 * @author leberre
47 *
48 * @see org.sat4j.specs.ISolver#addClause(IVecInt)
49 */
50 public class Minimal4InclusionModel extends SolverDecorator<ISolver> {
51
52 private static final long serialVersionUID = 1L;
53
54 /**
55 * @param solver
56 */
57 public Minimal4InclusionModel(ISolver solver) {
58 super(solver);
59 }
60
61 /*
62 * (non-Javadoc)
63 *
64 * @see org.sat4j.ISolver#model()
65 */
66 @SuppressWarnings("null")
67 @Override
68 public int[] model() {
69 int[] prevmodel = null;
70 IVecInt vec = new VecInt();
71 IVecInt cube = new VecInt();
72 // backUp();
73 try {
74 do {
75 prevmodel = super.model();
76 vec.clear();
77 cube.clear();
78 for (int q : prevmodel) {
79 if (q < 0) {
80 vec.push(-q);
81 } else {
82 cube.push(q);
83 }
84 }
85 addClause(vec);
86 } while (isSatisfiable(cube));
87 } catch (TimeoutException e) {
88 throw new IllegalStateException("Solver timed out");
89 } catch (ContradictionException e) {
90 // added trivial unsat clauses
91 }
92 // restore();
93 int[] newmodel = new int[vec.size()];
94 for (int i = 0, j = 0; i < prevmodel.length; i++) {
95 if (prevmodel[i] < 0) {
96 newmodel[j++] = prevmodel[i];
97 }
98 }
99
100 return newmodel;
101 }
102 }