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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.math4.legacy.genetics;
18  
19  import org.apache.commons.math4.legacy.exception.NumberIsTooSmallException;
20  
21  /**
22   * Stops after a fixed number of generations.
23   * <p>
24   * Each time {@link #isSatisfied(Population)} is invoked, a generation counter
25   * is incremented. Once the counter reaches the configured
26   * {@code maxGenerations} value, {@link #isSatisfied(Population)} returns true.
27   *
28   * @since 2.0
29   */
30  public class FixedGenerationCount implements StoppingCondition {
31      /** Number of generations that have passed. */
32      private int numGenerations;
33  
34      /** Maximum number of generations (stopping criteria). */
35      private final int maxGenerations;
36  
37      /**
38       * Create a new FixedGenerationCount instance.
39       *
40       * @param maxGenerations number of generations to evolve
41       * @throws NumberIsTooSmallException if the number of generations is &lt; 1
42       */
43      public FixedGenerationCount(final int maxGenerations) throws NumberIsTooSmallException {
44          if (maxGenerations <= 0) {
45              throw new NumberIsTooSmallException(maxGenerations, 1, true);
46          }
47          this.maxGenerations = maxGenerations;
48      }
49  
50      /**
51       * Determine whether or not the given number of generations have passed. Increments the number of generations
52       * counter if the maximum has not been reached.
53       *
54       * @param population ignored (no impact on result)
55       * @return <code>true</code> IFF the maximum number of generations has been exceeded
56       */
57      @Override
58      public boolean isSatisfied(final Population population) {
59          if (this.numGenerations < this.maxGenerations) {
60              numGenerations++;
61              return false;
62          }
63          return true;
64      }
65  
66      /**
67       * Returns the number of generations that have already passed.
68       * @return the number of generations that have passed
69       */
70      public int getNumGenerations() {
71          return numGenerations;
72      }
73  }