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.pb;
31
32 import java.io.PrintWriter;
33
34 import org.sat4j.core.VecInt;
35 import org.sat4j.specs.ContradictionException;
36 import org.sat4j.specs.IOptimizationProblem;
37 import org.sat4j.specs.IVecInt;
38 import org.sat4j.specs.TimeoutException;
39 import org.sat4j.tools.SolutionFoundListener;
40
41 /**
42 * Utility class to use optimization solvers instead of simple SAT solvers in
43 * code meant for SAT solvers.
44 *
45 * @author daniel
46 */
47 public class OptToPBSATAdapter extends PBSolverDecorator {
48
49 /**
50 *
51 */
52 private static final long serialVersionUID = 1L;
53
54 IOptimizationProblem problem;
55
56 private final IVecInt assumps = new VecInt();
57
58 private long begin;
59
60 private SolutionFoundListener sfl;
61
62 public OptToPBSATAdapter(IOptimizationProblem problem) {
63 this(problem, SolutionFoundListener.VOID);
64 }
65
66 public OptToPBSATAdapter(IOptimizationProblem problem,
67 SolutionFoundListener sfl) {
68 super((IPBSolver) problem);
69 this.problem = problem;
70 this.sfl = sfl;
71 }
72
73 @Override
74 public boolean isSatisfiable() throws TimeoutException {
75 return isSatisfiable(VecInt.EMPTY);
76 }
77
78 @Override
79 public boolean isSatisfiable(boolean global) throws TimeoutException {
80 return isSatisfiable();
81 }
82
83 @Override
84 public boolean isSatisfiable(IVecInt myAssumps, boolean global)
85 throws TimeoutException {
86 return isSatisfiable(myAssumps);
87 }
88
89 @Override
90 public boolean isSatisfiable(IVecInt myAssumps) throws TimeoutException {
91 this.assumps.clear();
92 myAssumps.copyTo(this.assumps);
93 this.begin = System.currentTimeMillis();
94 if (this.problem.hasNoObjectiveFunction()) {
95 return this.problem.isSatisfiable(myAssumps);
96 }
97 boolean satisfiable = false;
98 try {
99 while (this.problem.admitABetterSolution(myAssumps)) {
100 satisfiable = true;
101 sfl.onSolutionFound(this.problem.model());
102 this.problem.discardCurrentSolution();
103 if (isVerbose()) {
104 System.out.println(getLogPrefix()
105 + "Current objective function value: "
106 + this.problem.getObjectiveValue() + "("
107 + (System.currentTimeMillis() - this.begin)
108 / 1000.0 + "s)");
109 }
110 }
111 sfl.onUnsatTermination();
112 } catch (ContradictionException ce) {
113 sfl.onUnsatTermination();
114 }
115 return satisfiable;
116 }
117
118 @Override
119 public int[] model() {
120 return model(new PrintWriter(System.out, true));
121 }
122
123 /**
124 * Compute a minimal model according to the objective function of the
125 * IPBProblem decorated.
126 *
127 * @param out
128 * a writer to display information in verbose mode
129 * @since 2.3.2
130 */
131 public int[] model(PrintWriter out) {
132 return this.problem.model();
133 }
134
135 @Override
136 public boolean model(int var) {
137 return this.problem.model(var);
138 }
139
140 @Override
141 public String toString(String prefix) {
142 return prefix + "Optimization to Pseudo Boolean adapter\n"
143 + super.toString(prefix);
144 }
145
146 public boolean isOptimal() {
147 return this.problem.isOptimal();
148 }
149
150 /**
151 * Return the value of the objective function in the last model found.
152 *
153 * @return
154 * @since 2.3.2
155 */
156 public Number getCurrentObjectiveValue() {
157 return this.problem.getObjectiveValue();
158 }
159
160 /**
161 * Allow to set a specific timeout when the solver is in optimization mode.
162 * The solver internal timeout will be set to that value once it has found a
163 * solution. That way, the original timeout of the solver may be reduced if
164 * the solver finds quickly a solution, or increased if the solver finds
165 * regularly new solutions (thus giving more time to the solver each time).
166 *
167 * @see IOptimizationProblem#setTimeoutForFindingBetterSolution(int)
168 */
169 public void setTimeoutForFindingBetterSolution(int seconds) {
170 this.problem.setTimeoutForFindingBetterSolution(seconds);
171 }
172
173 public void setSolutionFoundListener(SolutionFoundListener sfl) {
174 this.sfl = sfl;
175 }
176 }