001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math.genetics;
018
019 /**
020 * Stops after a fixed number of generations. Each time
021 * {@link #isSatisfied(Population)} is invoked, a generation counter is
022 * incremented. Once the counter reaches the configured
023 * <code>maxGenerations</code> value, {@link #isSatisfied(Population)} returns
024 * true.
025 *
026 * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
027 * @since 2.0
028 */
029 public class FixedGenerationCount implements StoppingCondition {
030 /** Number of generations that have passed */
031 private int numGenerations = 0;
032
033 /** Maximum number of generations (stopping criteria) */
034 private final int maxGenerations;
035
036 /**
037 * Create a new FixedGenerationCount instance.
038 *
039 * @param maxGenerations number of generations to evolve
040 */
041 public FixedGenerationCount(int maxGenerations) {
042 if (maxGenerations <= 0)
043 throw new IllegalArgumentException("The number of generations has to be >= 0");
044 this.maxGenerations = maxGenerations;
045 }
046
047 /**
048 * Determine whether or not the given number of generations have passed.
049 * Increments the number of generations counter if the maximum has not
050 * been reached.
051 *
052 * @param population ignored (no impact on result)
053 * @return <code>true</code> IFF the maximum number of generations has been exceeded
054 */
055 public boolean isSatisfied(Population population) {
056 if (this.numGenerations < this.maxGenerations) {
057 numGenerations++;
058 return false;
059 }
060 return true;
061 }
062
063 /**
064 * @return the number of generations that have passed
065 */
066 public int getNumGenerations() {
067 return numGenerations;
068 }
069
070 }