FixedGenerationCount.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.genetics;

/**
 * Stops after a fixed number of generations.  Each time
 * {@link #isSatisfied(Population)} is invoked, a generation counter is
 * incremented.  Once the counter reaches the configured
 * <code>maxGenerations</code> value, {@link #isSatisfied(Population)} returns
 * true.
 *
 * @version $Id: FixedGenerationCount.java 1131229 2011-06-03 20:49:25Z luc $
 * @since 2.0
 */
public class FixedGenerationCount implements StoppingCondition {
    /** Number of generations that have passed */
    private int numGenerations = 0;

    /** Maximum number of generations (stopping criteria) */
    private final int maxGenerations;

    /**
     * Create a new FixedGenerationCount instance.
     *
     * @param maxGenerations number of generations to evolve
     */
    public FixedGenerationCount(int maxGenerations) {
        if (maxGenerations <= 0)
            throw new IllegalArgumentException("The number of generations has to be >= 0");
        this.maxGenerations = maxGenerations;
    }

    /**
     * Determine whether or not the given number of generations have passed.
     * Increments the number of generations counter if the maximum has not
     * been reached.
     *
     * @param population ignored (no impact on result)
     * @return <code>true</code> IFF the maximum number of generations has been exceeded
     */
    public boolean isSatisfied(Population population) {
        if (this.numGenerations < this.maxGenerations) {
            numGenerations++;
            return false;
        }
        return true;
    }

    /**
     * @return the number of generations that have passed
     */
    public int getNumGenerations() {
        return numGenerations;
    }

}