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 * That class allows to iterate through all the models (implicants) of a
38 * formula.
39 *
40 * <pre>
41 * ISolver solver = new ModelIterator(SolverFactory.OneSolver());
42 * boolean unsat = true;
43 * while (solver.isSatisfiable()) {
44 * unsat = false;
45 * int[] model = solver.model();
46 * // do something with model
47 * }
48 * if (unsat) {
49 * // UNSAT case
50 * }
51 * </pre>
52 *
53 * It is also possible to limit the number of models returned:
54 *
55 * <pre>
56 * ISolver solver = new ModelIterator(SolverFactory.OneSolver(), 10);
57 * </pre>
58 *
59 * will return at most 10 models.
60 *
61 * @author leberre
62 */
63 public class ModelIterator extends SolverDecorator<ISolver> {
64
65 private static final long serialVersionUID = 1L;
66
67 private boolean trivialfalsity = false;
68 private final int bound;
69 private int nbModelFound = 0;
70
71 /**
72 * @param solver
73 */
74 public ModelIterator(ISolver solver) {
75 this(solver, Integer.MAX_VALUE);
76 }
77
78 /**
79 *
80 * @param solver
81 * @param bound
82 * @since 2.1
83 */
84 public ModelIterator(ISolver solver, int bound) {
85 super(solver);
86 this.bound = bound;
87 }
88
89 /*
90 * (non-Javadoc)
91 *
92 * @see org.sat4j.ISolver#model()
93 */
94 @Override
95 public int[] model() {
96 int[] last = super.model();
97 nbModelFound++;
98 IVecInt clause = new VecInt(last.length);
99 for (int q : last) {
100 clause.push(-q);
101 }
102 try {
103 // System.out.println("adding " + clause);
104 addBlockingClause(clause);
105 } catch (ContradictionException e) {
106 trivialfalsity = true;
107 }
108 return last;
109 }
110
111 /*
112 * (non-Javadoc)
113 *
114 * @see org.sat4j.ISolver#isSatisfiable()
115 */
116 @Override
117 public boolean isSatisfiable() throws TimeoutException {
118 if (trivialfalsity || nbModelFound >= bound) {
119 return false;
120 }
121 trivialfalsity = false;
122 return super.isSatisfiable(true);
123 }
124
125 /*
126 * (non-Javadoc)
127 *
128 * @see org.sat4j.ISolver#isSatisfiable(org.sat4j.datatype.VecInt)
129 */
130 @Override
131 public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
132 if (trivialfalsity || nbModelFound >= bound) {
133 return false;
134 }
135 trivialfalsity = false;
136 return super.isSatisfiable(assumps, true);
137 }
138
139 /*
140 * (non-Javadoc)
141 *
142 * @see org.sat4j.ISolver#reset()
143 */
144 @Override
145 public void reset() {
146 trivialfalsity = false;
147 nbModelFound = 0;
148 super.reset();
149 }
150 }