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.core;
31
32 import java.io.Serializable;
33
34 /**
35 * The responsibility of that class is to choose the phase (positive or
36 * negative) of the variable that was selected by the IOrder.
37 *
38 * @author leberre
39 *
40 */
41 public interface IPhaseSelectionStrategy extends Serializable {
42
43 /**
44 * To be called when the activity of a literal changed.
45 *
46 * @param p
47 * a literal. The associated variable will be updated.
48 */
49 void updateVar(int p);
50
51 /**
52 * that method has the responsibility to initialize all arrays in the
53 * heuristics.
54 *
55 * @param nlength
56 * the number of variables managed by the heuristics.
57 */
58 void init(int nlength);
59
60 /**
61 * initialize the phase of a given variable to the given value. That method
62 * is suppose to be called AFTER init(int).
63 *
64 * @param var
65 * a variable
66 * @param p
67 * it's initial phase
68 */
69 void init(int var, int p);
70
71 /**
72 * indicate that a literal has been satisfied.
73 *
74 * @param p
75 */
76 void assignLiteral(int p);
77
78 /**
79 * selects the phase of the variable according to a phase selection
80 * strategy.
81 *
82 * @param var
83 * a variable chosen by the heuristics
84 * @return either var or not var, depending of the selection strategy.
85 *
86 */
87 int select(int var);
88
89 /**
90 * Allow to perform a specific action when a literal of the current decision
91 * level is updated. That method is called after {@link #updateVar(int)}.
92 *
93 * @param q
94 * a literal
95 */
96 void updateVarAtDecisionLevel(int q);
97 }