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 &lt; 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    }