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 * @since 2.0
027 */
028public class FixedGenerationCount implements StoppingCondition {
029    /** Number of generations that have passed */
030    private int numGenerations = 0;
031
032    /** Maximum number of generations (stopping criteria) */
033    private final int maxGenerations;
034
035    /**
036     * Create a new FixedGenerationCount instance.
037     *
038     * @param maxGenerations number of generations to evolve
039     * @throws NumberIsTooSmallException if the number of generations is &lt; 1
040     */
041    public FixedGenerationCount(final int maxGenerations) throws NumberIsTooSmallException {
042        if (maxGenerations <= 0) {
043            throw new NumberIsTooSmallException(maxGenerations, 1, true);
044        }
045        this.maxGenerations = maxGenerations;
046    }
047
048    /**
049     * Determine whether or not the given number of generations have passed. Increments the number of generations
050     * counter if the maximum has not 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(final Population population) {
056        if (this.numGenerations < this.maxGenerations) {
057            numGenerations++;
058            return false;
059        }
060        return true;
061    }
062
063    /**
064     * Returns the number of generations that have already passed.
065     * @return the number of generations that have passed
066     */
067    public int getNumGenerations() {
068        return numGenerations;
069    }
070
071}