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 java.util.ArrayList;
020import java.util.List;
021
022import org.apache.commons.math3.exception.MathIllegalArgumentException;
023import org.apache.commons.math3.exception.util.LocalizedFormats;
024
025/**
026 * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
027 * of the array representation to a random value uniformly distributed in [0,1].
028 *
029 * @since 2.0
030 * @version $Id: RandomKeyMutation.java 1416643 2012-12-03 19:37:14Z tn $
031 */
032public class RandomKeyMutation implements MutationPolicy {
033
034    /**
035     * {@inheritDoc}
036     *
037     * @throws MathIllegalArgumentException if <code>original</code> is not a {@link RandomKey} instance
038     */
039    public Chromosome mutate(final Chromosome original) throws MathIllegalArgumentException {
040        if (!(original instanceof RandomKey<?>)) {
041            throw new MathIllegalArgumentException(LocalizedFormats.RANDOMKEY_MUTATION_WRONG_CLASS,
042                                                   original.getClass().getSimpleName());
043        }
044
045        RandomKey<?> originalRk = (RandomKey<?>) original;
046        List<Double> repr = originalRk.getRepresentation();
047        int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
048
049        List<Double> newRepr = new ArrayList<Double> (repr);
050        newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
051
052        return originalRk.newFixedLengthChromosome(newRepr);
053    }
054
055}