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1   /*******************************************************************************
2    * SAT4J: a SATisfiability library for Java Copyright (C) 2004, 2012 Artois University and CNRS
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   * Contributors:
28   *   CRIL - initial API and implementation
29   *******************************************************************************/
30  package org.sat4j.minisat.learning;
31  
32  import org.sat4j.minisat.core.Constr;
33  import org.sat4j.minisat.core.DataStructureFactory;
34  import org.sat4j.minisat.core.ILits;
35  import org.sat4j.minisat.core.LearningStrategy;
36  import org.sat4j.minisat.core.Solver;
37  import org.sat4j.minisat.core.SolverStats;
38  import org.sat4j.minisat.core.VarActivityListener;
39  
40  /**
41   * Learn only clauses which size is smaller than a percentage of the number of
42   * variables.
43   * 
44   * @author leberre
45   */
46  public abstract class LimitedLearning<D extends DataStructureFactory>
47          implements LearningStrategy<D> {
48  
49      private static final long serialVersionUID = 1L;
50  
51      private final NoLearningButHeuristics<D> none;
52  
53      private final MiniSATLearning<D> all;
54  
55      protected ILits lits;
56  
57      private SolverStats stats;
58  
59      public LimitedLearning() {
60          this.none = new NoLearningButHeuristics<D>();
61          this.all = new MiniSATLearning<D>();
62      }
63  
64      public void setSolver(Solver<D> s) {
65          this.lits = s.getVocabulary();
66          setVarActivityListener(s);
67          this.all.setDataStructureFactory(s.getDSFactory());
68          this.stats = s.getStats();
69      }
70  
71      public void learns(Constr constr) {
72          if (learningCondition(constr)) {
73              this.all.learns(constr);
74          } else {
75              this.none.learns(constr);
76              this.stats.ignoredclauses++;
77          }
78      }
79  
80      abstract protected boolean learningCondition(Constr constr);
81  
82      public void init() {
83          this.all.init();
84          this.none.init();
85      }
86  
87      public void setVarActivityListener(VarActivityListener s) {
88          this.none.setVarActivityListener(s);
89          this.all.setVarActivityListener(s);
90      }
91  }