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.minisat.core;
29
30 import org.sat4j.specs.IConstr;
31 import org.sat4j.specs.IVecInt;
32
33 /*
34 * Created on 16 oct. 2003
35 */
36
37 /**
38 * Basic constraint abstraction used in Solver.
39 *
40 * Any new constraint type should implement that interface.
41 *
42 * @author leberre
43 */
44 public interface Constr extends Propagatable, IConstr {
45
46 /**
47 * Remove a constraint from the solver.
48 *
49 */
50 void remove();
51
52 /**
53 * Simplifies a constraint, by removing top level falsified literals for
54 * instance.
55 *
56 * @return true iff the constraint is satisfied.
57 */
58 boolean simplify();
59
60 /**
61 * Compute the reason for a given assignment.
62 *
63 * If the constraint is a clause, it is supposed to be either a unit clause
64 * or a falsified one.
65 *
66 * @param p
67 * a satisfied literal (or Lit.UNDEFINED)
68 * @param outReason
69 * the list of falsified literals whose negation is the reason of
70 * the assignment of p to true.
71 */
72 void calcReason(int p, IVecInt outReason);
73
74 /**
75 * Increase the constraint activity.
76 *
77 * @param claInc
78 * the value to increase the activity with
79 */
80 void incActivity(double claInc);
81
82 /**
83 * To obtain the activity of the constraint.
84 *
85 * @return the activity of the clause.
86 */
87 double getActivity();
88
89 /**
90 * Indicate wether a constraint is responsible from an assignment.
91 *
92 * @return true if a constraint is a "reason" for an assignment.
93 */
94 boolean locked();
95
96 /**
97 * Mark a constraint as learnt.
98 */
99
100 void setLearnt();
101
102 /**
103 * Register the constraint to the solver.
104 */
105 void register();
106
107 /**
108 * Rescale the clause activity by a value.
109 *
110 * @param d
111 * the value to rescale the clause activity with.
112 */
113 void rescaleBy(double d);
114
115 /**
116 * Method called when the constraint is to be asserted. It means that the
117 * constraint was learnt during the search and it should now propagate some
118 * truth values. In the clausal case, only one literal should be propagated.
119 * In other cases, it might be different.
120 *
121 * @param s
122 * a UnitPropagationListener to use for unit propagation.
123 */
124 void assertConstraint(UnitPropagationListener s);
125 }