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.constraints.card;
29
30 import java.io.Serializable;
31
32 import org.sat4j.minisat.constraints.cnf.Lits;
33 import org.sat4j.minisat.core.Constr;
34 import org.sat4j.minisat.core.ILits;
35 import org.sat4j.minisat.core.Undoable;
36 import org.sat4j.minisat.core.UnitPropagationListener;
37 import org.sat4j.specs.ContradictionException;
38 import org.sat4j.specs.IVecInt;
39
40 /**
41 * Cardinality constraint.
42 *
43 * @author leberre
44 */
45 public class AtLeast implements Constr, Undoable, Serializable {
46
47 private static final long serialVersionUID = 1L;
48
49 /** number of allowed falsified literal */
50 protected int maxUnsatisfied;
51
52 /** current number of falsified literals */
53 private int counter;
54
55 /**
56 * constraint literals
57 */
58 protected final int[] lits;
59
60 protected final ILits voc;
61
62 /**
63 * @param ps
64 * a vector of literals
65 * @param degree
66 * the minimal number of satisfied literals
67 */
68 protected AtLeast(ILits voc, IVecInt ps, int degree) {
69 maxUnsatisfied = ps.size() - degree;
70 this.voc = voc;
71 counter = 0;
72 lits = new int[ps.size()];
73 ps.moveTo(lits);
74 for (int q : lits) {
75 voc.attach(q ^ 1, this);
76 }
77 }
78
79 public static AtLeast atLeastNew(UnitPropagationListener s, ILits voc,
80 IVecInt ps, int n) throws ContradictionException {
81 int degree = Cards.niceParameters(s, voc, ps, n);
82 if (degree == 0)
83 return null;
84 return new AtLeast(voc, ps, degree);
85 }
86
87 /*
88 * (non-Javadoc)
89 *
90 * @see Constr#remove(Solver)
91 */
92 public void remove() {
93 for (int q : lits) {
94 voc.attaches(q ^ 1).remove(this);
95 }
96 }
97
98 /*
99 * (non-Javadoc)
100 *
101 * @see Constr#propagate(Solver, Lit)
102 */
103 public boolean propagate(UnitPropagationListener s, int p) {
104 // remet la clause dans la liste des clauses regardees
105 voc.attach(p, this);
106
107 if (counter == maxUnsatisfied)
108 return false;
109
110 counter++;
111 voc.undos(p).push(this);
112
113 // If no more can be false, enqueue the rest:
114 if (counter == maxUnsatisfied)
115 for (int q : lits) {
116 if (voc.isUnassigned(q) && !s.enqueue(q, this)) {
117 return false;
118 }
119 }
120 return true;
121 }
122
123 /*
124 * (non-Javadoc)
125 *
126 * @see Constr#simplify(Solver)
127 */
128 public boolean simplify() {
129 return false;
130 }
131
132 /*
133 * (non-Javadoc)
134 *
135 * @see Constr#undo(Solver, Lit)
136 */
137 public void undo(int p) {
138 counter--;
139 }
140
141 /*
142 * (non-Javadoc)
143 *
144 * @see Constr#calcReason(Solver, Lit, Vec)
145 */
146 public void calcReason(int p, IVecInt outReason) {
147 int c = (p == ILits.UNDEFINED) ? -1 : 0;
148 for (int q : lits) {
149 if (voc.isFalsified(q)) {
150 outReason.push(q ^ 1);
151 if (++c == maxUnsatisfied)
152 return;
153 }
154 }
155 }
156
157 /*
158 * (non-Javadoc)
159 *
160 * @see org.sat4j.minisat.datatype.Constr#learnt()
161 */
162 public boolean learnt() {
163 // Ces contraintes ne sont pas apprises pour le moment.
164 return false;
165 }
166
167 /*
168 * (non-Javadoc)
169 *
170 * @see org.sat4j.minisat.datatype.Constr#getActivity()
171 */
172 public double getActivity() {
173 // TODO Auto-generated method stub
174 return 0;
175 }
176
177 /*
178 * (non-Javadoc)
179 *
180 * @see org.sat4j.minisat.datatype.Constr#incActivity(double)
181 */
182 public void incActivity(double claInc) {
183 // TODO Auto-generated method stub
184
185 }
186
187 /*
188 * For learnt clauses only @author leberre
189 */
190 public boolean locked() {
191 // FIXME need to be adapted to AtLeast
192 // return lits[0].getReason() == this;
193 return true;
194 }
195
196 public void setLearnt() {
197 throw new UnsupportedOperationException();
198 }
199
200 public void register() {
201 throw new UnsupportedOperationException();
202 }
203
204 public int size() {
205 return lits.length;
206 }
207
208 public int get(int i) {
209 return lits[i];
210 }
211
212 public void rescaleBy(double d) {
213 throw new UnsupportedOperationException();
214 }
215
216 public void assertConstraint(UnitPropagationListener s) {
217 throw new UnsupportedOperationException();
218 }
219
220 /**
221 * Cha?ne repr?sentant la contrainte
222 *
223 * @return Cha?ne repr?sentant la contrainte
224 */
225 @Override
226 public String toString() {
227 StringBuffer stb = new StringBuffer();
228 stb.append("Card (" + lits.length + ") : ");
229 for (int i = 0; i < lits.length; i++) {
230 // if (voc.isUnassigned(lits[i])) {
231 stb.append(" + "); //$NON-NLS-1$
232 stb.append(Lits.toString(this.lits[i]));
233 stb.append("[");
234 stb.append(voc.valueToString(lits[i]));
235 stb.append("@");
236 stb.append(voc.getLevel(lits[i]));
237 stb.append("]");
238 stb.append(" ");
239 stb.append(" "); //$NON-NLS-1$
240 }
241 stb.append(">= "); //$NON-NLS-1$
242 stb.append(size() - maxUnsatisfied);
243
244 return stb.toString();
245 }
246
247 }