1 /*
2 * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2006 Daniel Le Berre
3 *
4 * Based on the original minisat specification from:
5 *
6 * An extensible SAT solver. Niklas E?n and Niklas S?rensson. Proceedings of the
7 * Sixth International Conference on Theory and Applications of Satisfiability
8 * Testing, LNCS 2919, pp 502-518, 2003.
9 *
10 * This library is free software; you can redistribute it and/or modify it under
11 * the terms of the GNU Lesser General Public License as published by the Free
12 * Software Foundation; either version 2.1 of the License, or (at your option)
13 * any later version.
14 *
15 * This library is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
18 * details.
19 *
20 * You should have received a copy of the GNU Lesser General Public License
21 * along with this library; if not, write to the Free Software Foundation, Inc.,
22 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 *
24 */
25
26 package org.sat4j.minisat.core;
27
28 import org.sat4j.specs.IConstr;
29 import org.sat4j.specs.IVecInt;
30
31 /*
32 * Created on 16 oct. 2003
33 */
34
35 /**
36 * Basic constraint abstraction used in Solver.
37 *
38 * Any new constraint type should implement that interface.
39 *
40 * @author leberre
41 */
42 public interface Constr extends Propagatable, IConstr {
43
44 /**
45 * Remove a constraint from the solver.
46 *
47 */
48 void remove();
49
50 /**
51 * Simplifies a constraint, by removing top level falsified literals for
52 * instance.
53 *
54 * @return true iff the constraint is satisfied.
55 */
56 boolean simplify();
57
58 /**
59 * Compute the reason for a given assignment.
60 *
61 * If the constraint is a clause, it is supposed to be either a unit clause
62 * or a falsified one.
63 *
64 * @param p
65 * a satisfied literal (or Lit.UNDEFINED)
66 * @param outReason
67 * the list of falsified literals whose negation is the reason of
68 * the assignment of p to true.
69 */
70 void calcReason(int p, IVecInt outReason);
71
72 /**
73 * Increase the constraint activity.
74 *
75 * @param claInc
76 * the value to increase the activity with
77 */
78 void incActivity(double claInc);
79
80 /**
81 * To obtain the activity of the constraint.
82 *
83 * @return the activity of the clause.
84 */
85 double getActivity();
86
87 /**
88 * Indicate wether a constraint is responsible from an assignment.
89 *
90 * @return true if a constraint is a "reason" for an assignment.
91 */
92 boolean locked();
93
94 /**
95 * Mark a constraint as learnt.
96 */
97
98 void setLearnt();
99
100 /**
101 * Register the constraint to the solver.
102 */
103 void register();
104
105 /**
106 * Rescale the clause activity by a value.
107 *
108 * @param d
109 * the value to rescale the clause activity with.
110 */
111 void rescaleBy(double d);
112
113 /**
114 * Method called when the constraint is to be asserted. It means that the
115 * constraint was learnt during the search and it should now propagate some
116 * truth values. In the clausal case, only one literal should be propagated.
117 * In other cases, it might be different.
118 *
119 * @param s
120 * a UnitPropagationListener to use for unit propagation.
121 */
122 void assertConstraint(UnitPropagationListener s);
123 }