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.math3.genetics;
018
019 import org.apache.commons.math3.exception.NumberIsTooSmallException;
020
021 /**
022 * Stops after a fixed number of generations. Each time {@link #isSatisfied(Population)} is invoked, a generation
023 * counter is incremented. Once the counter reaches the configured <code>maxGenerations</code> value,
024 * {@link #isSatisfied(Population)} returns true.
025 *
026 * @version $Id: FixedGenerationCount.java 1416643 2012-12-03 19:37:14Z tn $
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 * @throws NumberIsTooSmallException if the number of generations is < 1
041 */
042 public FixedGenerationCount(final int maxGenerations) throws NumberIsTooSmallException {
043 if (maxGenerations <= 0) {
044 throw new NumberIsTooSmallException(maxGenerations, 1, true);
045 }
046 this.maxGenerations = maxGenerations;
047 }
048
049 /**
050 * Determine whether or not the given number of generations have passed. Increments the number of generations
051 * counter if the maximum has not been reached.
052 *
053 * @param population ignored (no impact on result)
054 * @return <code>true</code> IFF the maximum number of generations has been exceeded
055 */
056 public boolean isSatisfied(final Population population) {
057 if (this.numGenerations < this.maxGenerations) {
058 numGenerations++;
059 return false;
060 }
061 return true;
062 }
063
064 /**
065 * Returns the number of generations that have already passed.
066 * @return the number of generations that have passed
067 */
068 public int getNumGenerations() {
069 return numGenerations;
070 }
071
072 }