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