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 */
017package org.apache.commons.math3.genetics;
018
019import 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 */
029public 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}