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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.math.genetics;
18  
19  /**
20   * Stops after a fixed number of generations.  Each time 
21   * {@link #isSatisfied(Population)} is invoked, a generation counter is
22   * incremented.  Once the counter reaches the configured 
23   * <code>maxGenerations</code> value, {@link #isSatisfied(Population)} returns
24   * true.
25   * 
26   * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
27   * @since 2.0
28   */
29  public class FixedGenerationCount implements StoppingCondition {
30      /** Number of generations that have passed */
31      private int numGenerations = 0;
32      
33      /** Maximum number of generations (stopping criteria) */
34      private final int maxGenerations;
35      
36      /**
37       * Create a new FixedGenerationCount instance.
38       * 
39       * @param maxGenerations number of generations to evolve
40       */
41      public FixedGenerationCount(int maxGenerations) {
42          if (maxGenerations <= 0) 
43              throw new IllegalArgumentException("The number of generations has to be >= 0");
44          this.maxGenerations = maxGenerations;
45      }
46      
47      /**
48       * Determine whether or not the given number of generations have passed.
49       * Increments the number of generations counter if the maximum has not
50       * been reached.
51       * 
52       * @param population ignored (no impact on result)
53       * @return <code>true</code> IFF the maximum number of generations has been exceeded
54       */
55      public boolean isSatisfied(Population population) {
56          if (this.numGenerations < this.maxGenerations) {
57              numGenerations++;
58              return false;
59          }
60          return true;
61      }
62  
63      /**
64       * @return the number of generations that have passed
65       */
66      public int getNumGenerations() {
67          return numGenerations;
68      }
69  
70  }