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.minisat.orders;
31
32 import static org.sat4j.core.LiteralsUtils.negLit;
33 import static org.sat4j.core.LiteralsUtils.posLit;
34
35 import java.util.Random;
36
37 import org.sat4j.minisat.core.IPhaseSelectionStrategy;
38
39 /**
40 * The variable selection strategy randomly picks one phase, either positive or
41 * negative.
42 *
43 * @author leberre
44 *
45 */
46 public final class RandomLiteralSelectionStrategy implements
47 IPhaseSelectionStrategy {
48
49 /**
50 *
51 */
52 private static final long serialVersionUID = 1L;
53
54 /**
55 * @since 2.2
56 */
57 public static final Random RAND = new Random(123456789);
58
59 public void assignLiteral(int p) {
60 }
61
62 public void init(int nlength) {
63 }
64
65 public void init(int var, int p) {
66 }
67
68 public int select(int var) {
69 if (RAND.nextBoolean()) {
70 return posLit(var);
71 }
72 return negLit(var);
73 }
74
75 public void updateVar(int p) {
76 }
77
78 public void updateVarAtDecisionLevel(int q) {
79 }
80
81 @Override
82 public String toString() {
83 return "random phase selection";
84 }
85 }