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.opt;
29
30 import org.sat4j.specs.ISolver;
31 import org.sat4j.specs.TimeoutException;
32 import org.sat4j.tools.SolverDecorator;
33
34 /**
35 * Abstract class which adds a new "selector" variable for each clause entered
36 * in the solver.
37 *
38 * As a consequence, an original problem with n variables and m clauses will end
39 * up with n+m variables.
40 *
41 * @author daniel
42 *
43 */
44 public abstract class AbstractSelectorVariablesDecorator extends
45 SolverDecorator<ISolver> {
46
47 /**
48 *
49 */
50 private static final long serialVersionUID = 1L;
51
52 protected int nborigvars;
53
54 private int nbexpectedclauses;
55
56 protected int nbnewvar;
57
58 protected int[] prevfullmodel;
59
60 private int [] prevmodel;
61 private boolean [] prevboolmodel;
62
63 public AbstractSelectorVariablesDecorator(ISolver solver) {
64 super(solver);
65 }
66
67 @Override
68 public int[] model() {
69 return prevmodel;
70 }
71
72 @Override
73 public boolean model(int var) {
74 return prevboolmodel[var-1];
75 }
76
77 @Override
78 public int newVar(int howmany) {
79 nborigvars = super.newVar(howmany);
80 return nborigvars;
81 }
82
83 @Override
84 public void setExpectedNumberOfClauses(int nb) {
85 nbexpectedclauses = nb;
86 super.setExpectedNumberOfClauses(nb);
87 super.newVar(nborigvars + nbexpectedclauses);
88 }
89
90 public int getExpectedNumberOfClauses() {
91 return nbexpectedclauses;
92 }
93
94 @Override
95 public void reset() {
96 super.reset();
97 nbnewvar = 0;
98 }
99
100 public boolean admitABetterSolution() throws TimeoutException {
101 boolean result = super.isSatisfiable(true);
102 if (result) {
103 prevfullmodel = super.model();
104 prevboolmodel = new boolean[nVars()];
105 for (int i=0;i<nVars();i++) {
106 prevboolmodel[i]=decorated().model(i+1);
107 }
108 int end = nborigvars - 1;
109 while (Math.abs(prevfullmodel[end]) > nborigvars)
110 end--;
111 prevmodel = new int[end + 1];
112 for (int i = 0; i <= end; i++) {
113 prevmodel[i] = prevfullmodel[i];
114 }
115 }
116 return result;
117 }
118
119 }