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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.learning;
29  
30  import org.sat4j.minisat.core.Constr;
31  import org.sat4j.minisat.core.DataStructureFactory;
32  import org.sat4j.minisat.core.ILits;
33  import org.sat4j.minisat.core.LearningStrategy;
34  import org.sat4j.minisat.core.Solver;
35  import org.sat4j.minisat.core.SolverStats;
36  import org.sat4j.minisat.core.VarActivityListener;
37  
38  /**
39   * Learn only clauses which size is smaller than a percentage of the number of
40   * variables.
41   * 
42   * @author leberre
43   */
44  public abstract class LimitedLearning<D extends DataStructureFactory> implements LearningStrategy<D> {
45  
46      private static final long serialVersionUID = 1L;
47  
48      private final NoLearningButHeuristics<D> none;
49  
50      private final MiniSATLearning<D> all;
51  
52      protected ILits lits;
53      
54      private SolverStats stats;
55  
56      public LimitedLearning() {
57          none = new NoLearningButHeuristics<D>();
58          all = new MiniSATLearning<D>();
59      }
60  
61      public void setSolver(Solver<D> s) {
62          this.lits = s.getVocabulary();
63          setVarActivityListener(s);
64          all.setDataStructureFactory(s.getDSFactory());
65          stats = s.getStats();
66      }
67  
68      public void learns(Constr constr) {
69          if (learningCondition(constr)) {
70              all.learns(constr);
71          } else {
72              none.learns(constr);
73              stats.ignoredclauses++;
74          }
75      }
76  
77      abstract protected boolean learningCondition(Constr constr);
78      
79      public void init() {
80          all.init();
81          none.init();
82      }
83  
84      public void setVarActivityListener(VarActivityListener s) {
85          none.setVarActivityListener(s);
86          all.setVarActivityListener(s);
87      }
88  }