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    }