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 java.math.BigInteger;
31
32 public final class ConflictMapSwitchToClause extends ConflictMap {
33
34 public static int UPPERBOUND;
35
36 public ConflictMapSwitchToClause(PBConstr cpb, int level) {
37 super(cpb, level);
38 }
39
40 public static IConflict createConflict(PBConstr cpb, int level) {
41 return new ConflictMapSwitchToClause(cpb, level);
42 }
43
44 /**
45 * reduces the constraint defined by wpb until the result of the cutting
46 * plane is a conflict. this reduction returns either a clause if .
47 *
48 * @param litImplied
49 * @param ind
50 * @param reducedCoefs
51 * @param wpb
52 * @return BigInteger.ONE
53 */
54 @Override
55 protected BigInteger reduceUntilConflict(int litImplied, int ind,
56 BigInteger[] reducedCoefs, WatchPb wpb) {
57 BigInteger degreeCons = super.reduceUntilConflict(litImplied, ind,
58 reducedCoefs, wpb);
59 // updating of the degree of the conflict
60 int i = 0;
61 for (; i < reducedCoefs.length
62 && reducedCoefs[i].equals(BigInteger.ZERO) && i != ind; i++) {
63 }
64 if (i < reducedCoefs.length) {
65 BigInteger bigCoef = reducedCoefs[i].multiply(coefMultCons);
66 if (weightedLits.containsKey(wpb.get(i)))
67 bigCoef = bigCoef.add(weightedLits.get(wpb.get(i)).multiply(
68 coefMult));
69 if (bigCoef.toString().length() > UPPERBOUND) {
70 // if we deal with really big integers
71 // reducing the constraint to a clause
72 numberOfReductions++;
73 hasBeenReduced = true;
74 degreeCons = reduceToClause(ind, wpb, reducedCoefs);
75 coefMultCons = weightedLits.get(litImplied ^ 1);
76 coefMult = BigInteger.ONE;
77 }
78 }
79 return degreeCons;
80 }
81
82 private BigInteger reduceToClause(int ind, WatchPb wpb,
83 BigInteger[] reducedCoefs) {
84 for (int i = 0; i < reducedCoefs.length; i++)
85 if (i == ind || wpb.getVocabulary().isFalsified(wpb.get(i)))
86 reducedCoefs[i] = BigInteger.ONE;
87 else
88 reducedCoefs[i] = BigInteger.ZERO;
89 return BigInteger.ONE;
90 }
91
92 }