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 pseudo boolean algorithms described in:
20 * A fast pseudo-Boolean constraint solver Chai, D.; Kuehlmann, A.
21 * Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on
22 * Volume 24, Issue 3, March 2005 Page(s): 305 - 317
23 *
24 * and
25 * Heidi E. Dixon, 2004. Automating Pseudo-Boolean Inference within a DPLL
26 * Framework. Ph.D. Dissertation, University of Oregon.
27 *******************************************************************************/
28 package org.sat4j.pb;
29
30 import org.sat4j.specs.ContradictionException;
31 import org.sat4j.specs.IOptimizationProblem;
32 import org.sat4j.specs.IVecInt;
33 import org.sat4j.specs.TimeoutException;
34
35 /**
36 * Utility class to use optimization solvers instead of simple SAT solvers in
37 * code meant for SAT solvers.
38 *
39 * @author daniel
40 */
41 public class OptToPBSATAdapter extends PBSolverDecorator {
42
43 /**
44 *
45 */
46 private static final long serialVersionUID = 1L;
47
48 IOptimizationProblem problem;
49
50 boolean modelComputed = false;
51
52 public OptToPBSATAdapter(IOptimizationProblem problem) {
53 super((IPBSolver) problem);
54 this.problem = problem;
55 }
56
57 @Override
58 public boolean isSatisfiable() throws TimeoutException {
59 modelComputed = false;
60 return problem.admitABetterSolution();
61 }
62
63 @Override
64 public boolean isSatisfiable(boolean global) throws TimeoutException {
65 return isSatisfiable();
66 }
67
68 @Override
69 public boolean isSatisfiable(IVecInt assumps, boolean global)
70 throws TimeoutException {
71 return isSatisfiable(assumps);
72 }
73
74 @Override
75 public boolean isSatisfiable(IVecInt assumps) throws TimeoutException {
76 throw new UnsupportedOperationException();
77 }
78
79 @Override
80 public int[] model() {
81 if (modelComputed)
82 return problem.model();
83 try {
84 assert problem.admitABetterSolution();
85 if (problem.hasNoObjectiveFunction()) {
86 return problem.model();
87 }
88 do {
89 problem.calculateObjective();
90 problem.discard();
91 } while (problem.admitABetterSolution());
92 } catch (TimeoutException e) {
93 // solver timeout
94 } catch (ContradictionException e) {
95 // OK, optimal model found
96 }
97 modelComputed = true;
98 return problem.model();
99 }
100
101 @Override
102 public boolean model(int var) {
103 if (!modelComputed) model();
104 return problem.model(var);
105 }
106
107 @Override
108 public String toString(String prefix) {
109 return prefix+"Optimization to Pseudo Boolean adapter\n"+super.toString(prefix);
110 }
111 }