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 number (with respect to cardinality) of
40 * negative literals. This is done be adding a constraint on the number of
41 * negative literals each time a model if found (the number of negative literals
42 * occuring in the model minus one).
43 *
44 * @author leberre
45 * @see org.sat4j.specs.ISolver#addAtMost(IVecInt, int)
46 */
47 public class Minimal4CardinalityModel extends SolverDecorator<ISolver> {
48
49 private static final long serialVersionUID = 1L;
50
51 /**
52 * @param solver
53 */
54 public Minimal4CardinalityModel(ISolver solver) {
55 super(solver);
56 }
57
58 /*
59 * (non-Javadoc)
60 *
61 * @see org.sat4j.ISolver#model()
62 */
63 @Override
64 public int[] model() {
65 int[] prevmodel = null;
66 IVecInt vec = new VecInt();
67 try {
68 do {
69 prevmodel = super.model();
70 vec.clear();
71 for (int i = 1; i <= nVars(); i++) {
72 vec.push(-i);
73 }
74 int counter = 0;
75 for (int q : prevmodel) {
76 if (q < 0) {
77 counter++;
78 }
79 }
80 addAtMost(vec, counter - 1);
81 } while (isSatisfiable());
82 } catch (TimeoutException e) {
83 throw new IllegalStateException("Solver timed out"); //$NON-NLS-1$
84 } catch (ContradictionException e) {
85 // added trivial unsat clauses
86 }
87 // restore();
88 return prevmodel;
89 }
90 }