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 pseudo boolean algorithms described in:
20 * A fast pseudo-Boolean constraint solver Chai, D.; Kuehlmann, A.
21 * Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on
22 * Volume 24, Issue 3, March 2005 Page(s): 305 - 317
23 *
24 * and
25 * Heidi E. Dixon, 2004. Automating Pseudo-Boolean Inference within a DPLL
26 * Framework. Ph.D. Dissertation, University of Oregon.
27 *******************************************************************************/
28 package org.sat4j.pb.constraints.pb;
29
30 import static org.sat4j.core.LiteralsUtils.neg;
31
32 import java.math.BigInteger;
33
34 import org.sat4j.minisat.constraints.cnf.HTClause;
35 import org.sat4j.minisat.core.ILits;
36 import org.sat4j.minisat.core.UnitPropagationListener;
37 import org.sat4j.specs.IVecInt;
38
39 public class HTClausePB extends HTClause implements PBConstr {
40
41 /**
42 *
43 */
44 private static final long serialVersionUID = 1L;
45
46 private boolean learnt;
47
48 public HTClausePB(IVecInt ps, ILits voc) {
49 super(ps, voc);
50 // TODO Auto-generated constructor stub
51 }
52
53 /*
54 * (non-Javadoc)
55 *
56 * @see org.sat4j.minisat.constraints.pb.PBConstr#getCoefficient(int)
57 */
58 public BigInteger getCoef(int literal) {
59 return BigInteger.ONE;
60 }
61
62 /*
63 * (non-Javadoc)
64 *
65 * @see org.sat4j.minisat.constraints.pb.PBConstr#getDegree()
66 */
67 public BigInteger getDegree() {
68 return BigInteger.ONE;
69 }
70
71 public BigInteger[] getCoefs() {
72 BigInteger[] tmp = new BigInteger[size()];
73 for (int i = 0; i < tmp.length; i++)
74 tmp[i] = BigInteger.ONE;
75 return tmp;
76 }
77
78 /**
79 * Creates a brand new clause, presumably from external data. Performs all
80 * sanity checks.
81 *
82 * @param s
83 * the object responsible for unit propagation
84 * @param voc
85 * the vocabulary
86 * @param literals
87 * the literals to store in the clause
88 * @return the created clause or null if the clause should be ignored
89 * (tautology for example)
90 */
91 public static HTClausePB brandNewClause(UnitPropagationListener s,
92 ILits voc, IVecInt literals) {
93 HTClausePB c = new HTClausePB(literals, voc);
94 c.register();
95 return c;
96 }
97
98 @Override
99 public void assertConstraint(UnitPropagationListener s) {
100 for (int i = 0; i < size(); i++)
101 if (getVocabulary().isUnassigned(get(i))) {
102 boolean ret = s.enqueue(get(i), this);
103 assert ret;
104 break;
105 }
106 }
107
108 public IVecInt computeAnImpliedClause() {
109 return null;
110 }
111
112 /**
113 * declares this clause as learnt
114 *
115 */
116 public void setLearnt() {
117 learnt = true;
118 }
119
120 /*
121 * (non-Javadoc)
122 *
123 * @see org.sat4j.minisat.datatype.Constr#learnt()
124 */
125 public boolean learnt() {
126 return learnt;
127 }
128
129 /**
130 * Register this clause which means watching the necessary literals If the
131 * clause is learnt, setLearnt() must be called before a call to register()
132 *
133 * @see #setLearnt()
134 */
135 public void register() {
136 if (learnt) {
137 if (middleLits.length > 0) {
138 // looking for the literal to put in tail
139 int maxi = 0;
140 int maxlevel = voc.getLevel(middleLits[0]);
141 for (int i = 1; i < middleLits.length; i++) {
142 int level = voc.getLevel(middleLits[i]);
143 if (level > maxlevel) {
144 maxi = i;
145 maxlevel = level;
146 }
147 }
148 if (maxlevel > voc.getLevel(tail)) {
149 int l = tail;
150 tail = middleLits[maxi];
151 middleLits[maxi] = l;
152 }
153 }
154 }
155
156 // watch both head and tail literals.
157 voc.attach(neg(head), this);
158 voc.attach(neg(tail), this);
159 }
160
161
162 }