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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  
33  /**
34   * A learning scheme for learning constraints of size smaller than a given
35   * constant.
36   * 
37   * @author leberre
38   */
39  public class FixedLengthLearning<D extends DataStructureFactory> extends LimitedLearning<D> {
40  
41      private static final long serialVersionUID = 1L;
42  
43      private int maxlength;
44  
45      private int bound;
46  
47      public FixedLengthLearning() {
48          this(3);
49      }
50  
51      public FixedLengthLearning(int maxlength) {
52          this.maxlength = maxlength;
53      }
54  
55      /*
56       * (non-Javadoc)
57       * 
58       * @see org.sat4j.minisat.LimitedLearning#learningCondition(org.sat4j.minisat.Constr)
59       */
60      @Override
61      public void init() {
62          setBound(maxlength);
63      }
64  
65      public void setMaxLength(int v) {
66          maxlength = v;
67      }
68  
69      public int getMaxLength() {
70          return maxlength;
71      }
72  
73      @Override
74      public String toString() {
75          return "Limit learning to clauses of size smaller or equal to " //$NON-NLS-1$
76                  + maxlength;
77      }
78  
79      protected void setBound(int newbound) {
80          bound = newbound;
81      }
82      
83      @Override
84      protected boolean learningCondition(Constr constr) {
85          return constr.size() <= bound;
86      }
87  
88  }