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
29 package org.sat4j.tools.encoding;
30
31 import org.sat4j.core.ConstrGroup;
32 import org.sat4j.core.VecInt;
33 import org.sat4j.specs.ContradictionException;
34 import org.sat4j.specs.IConstr;
35 import org.sat4j.specs.ISolver;
36 import org.sat4j.specs.IVecInt;
37
38 /**
39 *
40 * For the "at most one" case, this encoding is equivalent to the one referred
41 * to in the literature as the pair-wise or naive encoding. For the "at most k"
42 * case, the previous encoding is generalized with binomial selection.
43 *
44 * @author stephanieroussel
45 * @since 2.3.1
46 */
47 public class Binomial extends EncodingStrategyAdapter {
48
49 @Override
50 public IConstr addAtMost(ISolver solver, IVecInt literals, int degree)
51 throws ContradictionException {
52 ConstrGroup group = new ConstrGroup();
53
54 IVecInt clause = new VecInt();
55
56 for (IVecInt vec : literals.subset(degree + 1)) {
57 for (int i = 0; i < vec.size(); i++) {
58 clause.push(-vec.get(i));
59 }
60 group.add(solver.addClause(clause));
61 clause.clear();
62 }
63 return group;
64
65 }
66
67 @Override
68 public IConstr addAtMostOne(ISolver solver, IVecInt literals)
69 throws ContradictionException {
70 ConstrGroup group = new ConstrGroup();
71
72 VecInt clause = new VecInt();
73
74 for (int i = 0; i < literals.size() - 1; i++) {
75 for (int j = i + 1; j < literals.size(); j++) {
76 clause.push(-literals.get(i));
77 clause.push(-literals.get(j));
78 group.add(solver.addClause(clause));
79 clause.clear();
80 }
81 }
82 return group;
83 }
84
85 }