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.minisat.orders;
29
30 import static org.sat4j.core.LiteralsUtils.negLit;
31 import static org.sat4j.core.LiteralsUtils.posLit;
32
33 import java.util.Random;
34
35 import org.sat4j.minisat.core.IPhaseSelectionStrategy;
36
37 /**
38 * The variable selection strategy randomly picks one phase, either positive or negative.
39 *
40 * @author leberre
41 *
42 */
43 public class RandomLiteralSelectionStrategy implements IPhaseSelectionStrategy {
44
45 /**
46 *
47 */
48 private static final long serialVersionUID = 1L;
49
50 public static final Random rand = new Random(123456789);
51
52 public void assignLiteral(int p) {
53 }
54
55 public void init(int nlength) {
56 }
57
58 public void init(int var, int p) {
59 }
60
61 public int select(int var) {
62 if (rand.nextBoolean()) {
63 return posLit(var);
64 }
65 return negLit(var);
66 }
67
68 public void updateVar(int p) {
69 }
70
71 @Override
72 public String toString() {
73 return "random phase selection";
74 }
75 }