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 * The responsibility of that class is to choose the phase (positive or
34 * negative) of the variable that was selected by the IOrder.
35 *
36 * @author leberre
37 *
38 */
39 public interface IPhaseSelectionStrategy extends Serializable {
40
41 /**
42 * To be called when the activity of a literal changed.
43 *
44 * @param p
45 * a literal. The associated variable will be updated.
46 */
47 void updateVar(int p);
48
49 /**
50 * that method has the responsibility to initialize all arrays in the
51 * heuristics.
52 *
53 * @param nlength
54 * the number of variables managed by the heuristics.
55 */
56 void init(int nlength);
57
58 /**
59 * initialize the phase of a given variable to the given value. That method
60 * is suppose to be called AFTER init(int).
61 *
62 * @param var
63 * a variable
64 * @param p
65 * it's initial phase
66 */
67 void init(int var, int p);
68
69 /**
70 * indicate that a literal has been satisfied.
71 *
72 * @param p
73 */
74 void assignLiteral(int p);
75
76 /**
77 * selects the phase of the variable according to a phase selection
78 * strategy.
79 *
80 * @param var
81 * a variable chosen by the heuristics
82 * @return either var or not var, depending of the selection strategy.
83 *
84 */
85 int select(int var);
86
87 /**
88 * Allow to perform a specific action when a literal of the current decision
89 * level is updated. That method is called after {@link #updateVar(int)}.
90 *
91 * @param q
92 * a literal
93 */
94 void updateVarAtDecisionLevel(int q);
95 }