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.minisat.core;
31
32 import org.sat4j.specs.IConstr;
33 import org.sat4j.specs.IVecInt;
34 import org.sat4j.specs.UnitPropagationListener;
35
36 /*
37 * Created on 16 oct. 2003
38 */
39
40 /**
41 * Basic constraint abstraction used in Solver.
42 *
43 * Any new constraint type should implement that interface.
44 *
45 * @author leberre
46 */
47 public interface Constr extends IConstr {
48
49 /**
50 * Remove a constraint from the solver.
51 *
52 * @param upl
53 * @since 2.1
54 */
55 void remove(UnitPropagationListener upl);
56
57 /**
58 * Simplifies a constraint, by removing top level falsified literals for
59 * instance.
60 *
61 * @return true iff the constraint is satisfied and can be removed from the
62 * database.
63 */
64 boolean simplify();
65
66 /**
67 * Compute the reason for a given assignment.
68 *
69 * If the constraint is a clause, it is supposed to be either a unit clause
70 * or a falsified one. It is expected that the falsification of the
71 * constraint has been detected as soon at is occurs (e.g. using
72 * {@link Propagatable#propagate(UnitPropagationListener, int)}.
73 *
74 *
75 * @param p
76 * a satisfied literal (or Lit.UNDEFINED)
77 * @param outReason
78 * the list of falsified literals whose negation is the reason of
79 * the assignment of p to true.
80 */
81 void calcReason(int p, IVecInt outReason);
82
83 /**
84 * Compute the reason for a given assignment in a the constraint created on
85 * the fly in the solver. Compared to the method
86 * {@link #calcReason(int, IVecInt)}, the falsification may not have been
87 * detected as soon as possible. As such, it is necessary to take into
88 * account the order of the literals in the trail.
89 *
90 * @param p
91 * a satisfied literal (or Lit.UNDEFINED)
92 * @param trail
93 * all the literals satisfied in the solvers, should not be
94 * modified.
95 * @param outReason
96 * a list of falsified literals whose negation is the reason of
97 * the assignment of p to true.
98 * @since 2.3.3
99 */
100 void calcReasonOnTheFly(int p, IVecInt trail, IVecInt outReason);
101
102 /**
103 * Increase the constraint activity.
104 *
105 * @param claInc
106 * the value to increase the activity with
107 */
108 void incActivity(double claInc);
109
110 /**
111 *
112 * @param claInc
113 * @since 2.1
114 *
115 */
116 @Deprecated
117 void forwardActivity(double claInc);
118
119 /**
120 * Indicate wether a constraint is responsible from an assignment.
121 *
122 * @return true if a constraint is a "reason" for an assignment.
123 */
124 boolean locked();
125
126 /**
127 * Mark a constraint as learnt.
128 */
129
130 void setLearnt();
131
132 /**
133 * Register the constraint to the solver.
134 */
135 void register();
136
137 /**
138 * Rescale the clause activity by a value.
139 *
140 * @param d
141 * the value to rescale the clause activity with.
142 */
143 void rescaleBy(double d);
144
145 /**
146 * Set the activity at a specific value
147 *
148 * @param d
149 * the new activity
150 * @since 2.3.1
151 */
152 void setActivity(double d);
153
154 /**
155 * Method called when the constraint is to be asserted. It means that the
156 * constraint was learned during the search and it should now propagate some
157 * truth values. In the clausal case, only one literal should be propagated.
158 * In other cases, it might be different.
159 *
160 * @param s
161 * a UnitPropagationListener to use for unit propagation.
162 */
163 void assertConstraint(UnitPropagationListener s);
164
165 /**
166 * Method called when the constraint is added to the solver "on the fly". In
167 * that case, the constraint may or may not have to propagate some literals,
168 * unlike the {@link #assertConstraint(UnitPropagationListener)} method.
169 *
170 * @param s
171 * a UnitPropagationListener to use for unit propagation.
172 * @since 2.3.4
173 */
174 void assertConstraintIfNeeded(UnitPropagationListener s);
175
176 }