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.specs;
29
30 import java.io.PrintWriter;
31
32 /**
33 * Access to the information related to a given problem instance.
34 *
35 * @author leberre
36 */
37 public interface IProblem {
38 /**
39 * Provide a model (if any) for a satisfiable formula. That method should be
40 * called AFTER isSatisfiable() or isSatisfiable(IVecInt) if the formula is
41 * satisfiable. Else an exception UnsupportedOperationException is launched.
42 *
43 * @return a model of the formula as an array of literals to satisfy.
44 * @see #isSatisfiable()
45 * @see #isSatisfiable(IVecInt)
46 */
47 int[] model();
48
49 /**
50 * Provide the truth value of a specific variable in the model. That method
51 * should be called AFTER isSatisfiable() if the formula is satisfiable.
52 * Else an exception UnsupportedOperationException is launched.
53 *
54 * @param var
55 * the variable id in Dimacs format
56 * @return the truth value of that variable in the model
57 * @since 1.6
58 * @see #model()
59 */
60 boolean model(int var);
61
62 /**
63 * Provide a prime implicant, i.e. a set of literal that is sufficient to
64 * satisfy all constraints of the problem.
65 *
66 * NOTE THAT THIS FEATURE IS HIGHLY EXPERIMENTAL FOR NOW.
67 *
68 * @return a prime implicant of the formula as an array of literal, Dimacs
69 * format.
70 * @since 2.3
71 */
72 int[] primeImplicant();
73
74 /**
75 * Check the satisfiability of the set of constraints contained inside the
76 * solver.
77 *
78 * @return true if the set of constraints is satisfiable, else false.
79 */
80 boolean isSatisfiable() throws TimeoutException;
81
82 /**
83 * Check the satisfiability of the set of constraints contained inside the
84 * solver.
85 *
86 * @param assumps
87 * a set of literals (represented by usual non null integers in
88 * Dimacs format).
89 * @param globalTimeout
90 * whether that call is part of a global process (i.e.
91 * optimization) or not. if (global), the timeout will not be
92 * reset between each call.
93 * @return true if the set of constraints is satisfiable when literals are
94 * satisfied, else false.
95 */
96 boolean isSatisfiable(IVecInt assumps, boolean globalTimeout)
97 throws TimeoutException;
98
99 /**
100 * Check the satisfiability of the set of constraints contained inside the
101 * solver.
102 *
103 * @param globalTimeout
104 * whether that call is part of a global process (i.e.
105 * optimization) or not. if (global), the timeout will not be
106 * reset between each call.
107 * @return true if the set of constraints is satisfiable, else false.
108 */
109 boolean isSatisfiable(boolean globalTimeout) throws TimeoutException;
110
111 /**
112 * Check the satisfiability of the set of constraints contained inside the
113 * solver.
114 *
115 * @param assumps
116 * a set of literals (represented by usual non null integers in
117 * Dimacs format).
118 * @return true if the set of constraints is satisfiable when literals are
119 * satisfied, else false.
120 */
121 boolean isSatisfiable(IVecInt assumps) throws TimeoutException;
122
123 /**
124 * Look for a model satisfying all the clauses available in the problem. It
125 * is an alternative to isSatisfiable() and model() methods, as shown in the
126 * pseudo-code: <code>
127 if (isSatisfiable()) {
128 return model();
129 }
130 return null;
131 </code>
132 *
133 * @return a model of the formula as an array of literals to satisfy, or
134 * <code>null</code> if no model is found
135 * @throws TimeoutException
136 * if a model cannot be found within the given timeout.
137 * @since 1.7
138 */
139 int[] findModel() throws TimeoutException;
140
141 /**
142 * Look for a model satisfying all the clauses available in the problem. It
143 * is an alternative to isSatisfiable(IVecInt) and model() methods, as shown
144 * in the pseudo-code: <code>
145 if (isSatisfiable(assumpt)) {
146 return model();
147 }
148 return null;
149 </code>
150 *
151 * @return a model of the formula as an array of literals to satisfy, or
152 * <code>null</code> if no model is found
153 * @throws TimeoutException
154 * if a model cannot be found within the given timeout.
155 * @since 1.7
156 */
157 int[] findModel(IVecInt assumps) throws TimeoutException;
158
159 /**
160 * To know the number of constraints currently available in the solver.
161 * (without taking into account learned constraints).
162 *
163 * @return the number of constraints added to the solver
164 */
165 int nConstraints();
166
167 /**
168 * Declare <code>howmany</code> variables in the problem (and thus in the
169 * vocabulary), that will be represented using the Dimacs format by integers
170 * ranging from 1 to howmany. That feature allows encodings to create
171 * additional variables with identifier starting at howmany+1.
172 *
173 * @param howmany
174 * number of variables to create
175 * @return the total number of variables available in the solver (the
176 * highest variable number)
177 * @see #nVars()
178 */
179 int newVar(int howmany);
180
181 /**
182 * To know the number of variables used in the solver as declared by
183 * newVar()
184 *
185 * In case the method newVar() has not been used, the method returns the
186 * number of variables used in the solver.
187 *
188 * @return the number of variables created using newVar().
189 * @see #newVar(int)
190 */
191 int nVars();
192
193 /**
194 * To print additional informations regarding the problem.
195 *
196 * @param out
197 * the place to print the information
198 * @param prefix
199 * the prefix to put in front of each line
200 */
201 void printInfos(PrintWriter out, String prefix);
202
203 }