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.core;
29
30 import java.io.Serializable;
31
32
33 /**
34 * The responsibility of that class is to choose the phase (positive or negative)
35 * of the variable that was selected by the IOrder.
36 *
37 * @author leberre
38 *
39 */
40 public interface IPhaseSelectionStrategy extends Serializable {
41
42 /**
43 * To be called when the activity of a literal changed.
44 *
45 * @param p
46 * a literal. The associated variable will be updated.
47 */
48 void updateVar(int p);
49
50 /**
51 * that method has the responsibility to initialize all arrays in the
52 * heuristics.
53 * @param nlength the number of variables managed by the heuristics.
54 */
55 void init(int nlength);
56
57 /**
58 * initialize the phase of a given variable to the given value.
59 * That method is suppose to be called AFTER init(int).
60 *
61 * @param var a variable
62 * @param p it's initial phase
63 */
64 void init(int var, int p);
65
66 /**
67 * indicate that a literal has been satisfied.
68 *
69 * @param p
70 */
71 void assignLiteral(int p);
72
73 /**
74 * selects the phase of the variable according to a phase
75 * selection strategy.
76 *
77 * @param var a variable chosen by the heuristics
78 * @return either var or not var, depending of the selection strategy.
79 *
80 */
81 int select(int var);
82 }