1 /*******************************************************************************
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2006 Daniel Le
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 package org.sat4j.csp;
20
21 import org.sat4j.core.ASolverFactory;
22 import org.sat4j.minisat.constraints.MixedDataStructureDanielWL;
23 import org.sat4j.minisat.core.DataStructureFactory;
24 import org.sat4j.minisat.core.ILits;
25 import org.sat4j.minisat.core.Solver;
26 import org.sat4j.minisat.learning.MiniSATLearning;
27 import org.sat4j.minisat.orders.VarOrderHeap;
28 import org.sat4j.minisat.restarts.MiniSATRestarts;
29 import org.sat4j.minisat.uip.FirstUIP;
30 import org.sat4j.specs.ISolver;
31 import org.sat4j.tools.DimacsOutputSolver;
32
33 /**
34 * User friendly access to pre-constructed solvers.
35 *
36 * @author leberre
37 */
38 public class SolverFactory extends ASolverFactory<ISolver> {
39
40 /**
41 *
42 */
43 private static final long serialVersionUID = 1L;
44
45 // thread safe implementation of the singleton design pattern
46 private static SolverFactory instance;
47
48 /**
49 * Private constructor. Use singleton method instance() instead.
50 *
51 * @see #instance()
52 */
53 private SolverFactory() {
54 super();
55 }
56
57 private static synchronized void createInstance() {
58 if (instance == null) {
59 instance = new SolverFactory();
60 }
61 }
62
63 /**
64 * Access to the single instance of the factory.
65 *
66 * @return the singleton of that class.
67 */
68 public static SolverFactory instance() {
69 if (instance == null) {
70 createInstance();
71 }
72 return instance;
73 }
74
75 /**
76 * @param dsf
77 * the data structure used for representing clauses and lits
78 * @return MiniSAT the data structure dsf.
79 */
80 public static <L extends ILits> Solver<DataStructureFactory> newMiniSAT(
81 DataStructureFactory dsf) {
82 MiniSATLearning<DataStructureFactory> learning = new MiniSATLearning<DataStructureFactory>();
83 Solver<DataStructureFactory> solver = new Solver<DataStructureFactory>(new FirstUIP(), learning, dsf,
84 new VarOrderHeap(), new MiniSATRestarts());
85 learning.setDataStructureFactory(solver.getDSFactory());
86 learning.setVarActivityListener(solver);
87 return solver;
88 }
89
90
91
92 /**
93 * Default solver of the SolverFactory. This solver is meant to be used on
94 * challenging SAT benchmarks.
95 *
96 * @return the best "general purpose" SAT solver available in the factory.
97 * @see #defaultSolver() the same method, polymorphic, to be called from an
98 * instance of ASolverFactory.
99 */
100 public static ISolver newDefault() {
101 Solver<DataStructureFactory> solver = newMiniSAT(new MixedDataStructureDanielWL());
102 solver.setSimplifier(solver.EXPENSIVE_SIMPLIFICATION);
103 return solver;
104 }
105
106 @Override
107 public ISolver defaultSolver() {
108 return newDefault();
109 }
110
111 /**
112 * Small footprint SAT solver.
113 *
114 * @return a SAT solver suitable for solving small/easy SAT benchmarks.
115 * @see #lightSolver() the same method, polymorphic, to be called from an
116 * instance of ASolverFactory.
117 */
118 public static ISolver newLight() {
119 return newMiniSAT(new MixedDataStructureDanielWL());
120 }
121
122 @Override
123 public ISolver lightSolver() {
124 return newLight();
125 }
126
127 public static ISolver newDimacsOutput() {
128 return new DimacsOutputSolver();
129 }
130
131 }