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;
29
30 import java.io.PrintWriter;
31
32 import org.sat4j.specs.ContradictionException;
33 import org.sat4j.specs.IOptimizationProblem;
34 import org.sat4j.specs.IProblem;
35 import org.sat4j.specs.TimeoutException;
36
37 /**
38 * This class is intended to be used by launchers to solve optimization
39 * problems, i.e. problems for which a loop is needed to find the optimal
40 * solution.
41 *
42 * @author leberre
43 *
44 */
45 public abstract class AbstractOptimizationLauncher extends AbstractLauncher {
46
47 /**
48 *
49 */
50 private static final long serialVersionUID = 1L;
51
52 private static final String CURRENT_OPTIMUM_VALUE_PREFIX = "o "; //$NON-NLS-1$
53
54 @Override
55 protected void displayResult() {
56 displayAnswer();
57
58 log("Total wall clock time (in seconds): " //$NON-NLS-1$
59 + (System.currentTimeMillis() - getBeginTime()) / 1000.0);
60 }
61
62 protected void displayAnswer(){
63 if (solver == null)
64 return;
65 PrintWriter out = getLogWriter();
66 solver.printStat(out, COMMENT_PREFIX);
67 ExitCode exitCode = getExitCode();
68 out.println(ANSWER_PREFIX + exitCode);
69 if (exitCode == ExitCode.SATISFIABLE
70 || exitCode == ExitCode.OPTIMUM_FOUND) {
71 out.print(SOLUTION_PREFIX);
72 getReader().decode(solver.model(), out);
73 out.println();
74 IOptimizationProblem optproblem = (IOptimizationProblem) solver;
75 if (!optproblem.hasNoObjectiveFunction()) {
76 log("objective function=" + optproblem.calculateObjective()); //$NON-NLS-1$
77 }
78 }
79 }
80
81 @Override
82 protected void solve(IProblem problem) throws TimeoutException {
83 boolean isSatisfiable = false;
84
85 IOptimizationProblem optproblem = (IOptimizationProblem) problem;
86
87 try {
88 while (optproblem.admitABetterSolution()) {
89 if (!isSatisfiable) {
90 if (optproblem.nonOptimalMeansSatisfiable()) {
91 setExitCode(ExitCode.SATISFIABLE);
92 if (optproblem.hasNoObjectiveFunction()) {
93 return;
94 }
95 log("SATISFIABLE"); //$NON-NLS-1$
96 }
97 isSatisfiable = true;
98 log("OPTIMIZING..."); //$NON-NLS-1$
99 }
100 log("Got one! Elapsed wall clock time (in seconds):" //$NON-NLS-1$
101 + (System.currentTimeMillis() - getBeginTime())
102 / 1000.0);
103 getLogWriter().println(
104 CURRENT_OPTIMUM_VALUE_PREFIX
105 + optproblem.calculateObjective());
106 optproblem.discard();
107 }
108 if (isSatisfiable) {
109 setExitCode(ExitCode.OPTIMUM_FOUND);
110 } else {
111 setExitCode(ExitCode.UNSATISFIABLE);
112 }
113 } catch (ContradictionException ex) {
114 assert isSatisfiable;
115 setExitCode(ExitCode.OPTIMUM_FOUND);
116 }
117 }
118
119 }