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.specs;
31
32 import java.io.PrintWriter;
33
34 /**
35 * Access to the information related to a given problem instance.
36 *
37 * @author leberre
38 */
39 public interface IProblem {
40 /**
41 * Provide a model (if any) for a satisfiable formula. That method should be
42 * called AFTER isSatisfiable() or isSatisfiable(IVecInt) if the formula is
43 * satisfiable. Else an exception UnsupportedOperationException is launched.
44 *
45 * @return a model of the formula as an array of literals to satisfy.
46 * @see #isSatisfiable()
47 * @see #isSatisfiable(IVecInt)
48 */
49 int[] model();
50
51 /**
52 * Provide the truth value of a specific variable in the model. That method
53 * should be called AFTER isSatisfiable() if the formula is satisfiable.
54 * Else an exception UnsupportedOperationException is launched.
55 *
56 * @param var
57 * the variable id in Dimacs format
58 * @return the truth value of that variable in the model
59 * @since 1.6
60 * @see #model()
61 */
62 boolean model(int var);
63
64 /**
65 * Provide a prime implicant, i.e. a set of literal that is sufficient to
66 * satisfy all constraints of the problem.
67 *
68 *
69 * @return a prime implicant of the formula as an array of literal, Dimacs
70 * format.
71 * @since 2.3
72 */
73 int[] primeImplicant();
74
75 /**
76 * Check if a given literal is part of the prime implicant computed by the
77 * {@link #primeImplicant()} method.
78 *
79 * @param p
80 * a literal in Dimacs format
81 * @return true iff p belongs to {@link #primeImplicant()}
82 */
83 boolean primeImplicant(int p);
84
85 /**
86 * Check the satisfiability of the set of constraints contained inside the
87 * solver.
88 *
89 * @return true if the set of constraints is satisfiable, else false.
90 */
91 boolean isSatisfiable() throws TimeoutException;
92
93 /**
94 * Check the satisfiability of the set of constraints contained inside the
95 * solver.
96 *
97 * @param assumps
98 * a set of literals (represented by usual non null integers in
99 * Dimacs format).
100 * @param globalTimeout
101 * whether that call is part of a global process (i.e.
102 * optimization) or not. if (global), the timeout will not be
103 * reset between each call.
104 * @return true if the set of constraints is satisfiable when literals are
105 * satisfied, else false.
106 */
107 boolean isSatisfiable(IVecInt assumps, boolean globalTimeout)
108 throws TimeoutException;
109
110 /**
111 * Check the satisfiability of the set of constraints contained inside the
112 * solver.
113 *
114 * @param globalTimeout
115 * whether that call is part of a global process (i.e.
116 * optimization) or not. if (global), the timeout will not be
117 * reset between each call.
118 * @return true if the set of constraints is satisfiable, else false.
119 */
120 boolean isSatisfiable(boolean globalTimeout) throws TimeoutException;
121
122 /**
123 * Check the satisfiability of the set of constraints contained inside the
124 * solver.
125 *
126 * @param assumps
127 * a set of literals (represented by usual non null integers in
128 * Dimacs format).
129 * @return true if the set of constraints is satisfiable when literals are
130 * satisfied, else false.
131 */
132 boolean isSatisfiable(IVecInt assumps) throws TimeoutException;
133
134 /**
135 * Look for a model satisfying all the clauses available in the problem. It
136 * is an alternative to isSatisfiable() and model() methods, as shown in the
137 * pseudo-code: <code>
138 if (isSatisfiable()) {
139 return model();
140 }
141 return null;
142 </code>
143 *
144 * @return a model of the formula as an array of literals to satisfy, or
145 * <code>null</code> if no model is found
146 * @throws TimeoutException
147 * if a model cannot be found within the given timeout.
148 * @since 1.7
149 */
150 int[] findModel() throws TimeoutException;
151
152 /**
153 * Look for a model satisfying all the clauses available in the problem. It
154 * is an alternative to isSatisfiable(IVecInt) and model() methods, as shown
155 * in the pseudo-code: <code>
156 if (isSatisfiable(assumpt)) {
157 return model();
158 }
159 return null;
160 </code>
161 *
162 * @return a model of the formula as an array of literals to satisfy, or
163 * <code>null</code> if no model is found
164 * @throws TimeoutException
165 * if a model cannot be found within the given timeout.
166 * @since 1.7
167 */
168 int[] findModel(IVecInt assumps) throws TimeoutException;
169
170 /**
171 * To know the number of constraints currently available in the solver.
172 * (without taking into account learned constraints).
173 *
174 * @return the number of constraints added to the solver
175 */
176 int nConstraints();
177
178 /**
179 * Declare <code>howmany</code> variables in the problem (and thus in the
180 * vocabulary), that will be represented using the Dimacs format by integers
181 * ranging from 1 to howmany. That feature allows encodings to create
182 * additional variables with identifier starting at howmany+1.
183 *
184 * @param howmany
185 * number of variables to create
186 * @return the total number of variables available in the solver (the
187 * highest variable number)
188 * @see #nVars()
189 */
190 int newVar(int howmany);
191
192 /**
193 * To know the number of variables used in the solver as declared by
194 * newVar()
195 *
196 * In case the method newVar() has not been used, the method returns the
197 * number of variables used in the solver.
198 *
199 * @return the number of variables created using newVar().
200 * @see #newVar(int)
201 */
202 int nVars();
203
204 /**
205 * To print additional informations regarding the problem.
206 *
207 * @param out
208 * the place to print the information
209 * @param prefix
210 * the prefix to put in front of each line
211 */
212 void printInfos(PrintWriter out, String prefix);
213
214 }