MutateShuffle.java

/*
 * Artificial Intelligence for Humans
 * Volume 2: Nature Inspired Algorithms
 * Java Version
 * http://www.aifh.org
 * http://www.jeffheaton.com
 *
 * Code repository:
 * https://github.com/jeffheaton/aifh
 *
 * Copyright 2014 by Jeff Heaton
 *
 * Licensed 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.
 *
 * For more information on Heaton Research copyrights, licenses
 * and trademarks visit:
 * http://www.heatonresearch.com/copyright
 */
package com.heatonresearch.aifh.genetic.mutate;

import com.heatonresearch.aifh.evolutionary.genome.Genome;
import com.heatonresearch.aifh.evolutionary.opp.EvolutionaryOperator;
import com.heatonresearch.aifh.evolutionary.train.EvolutionaryAlgorithm;
import com.heatonresearch.aifh.genetic.genome.ArrayGenome;
import com.heatonresearch.aifh.randomize.GenerateRandom;

/**
 * A simple mutation where genes are shuffled. This mutation will not produce
 * repeated genes.
 */
public class MutateShuffle implements EvolutionaryOperator {

    /**
     * The owner.
     */
    private EvolutionaryAlgorithm owner;

    /**
     * {@inheritDoc}
     */
    @Override
    public void init(final EvolutionaryAlgorithm theOwner) {
        this.owner = theOwner;
    }

    /**
     * @return The number of offspring produced, which is 1 for this mutation.
     */
    @Override
    public int offspringProduced() {
        return 1;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int parentsNeeded() {
        return 1;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void performOperation(final GenerateRandom rnd, final Genome[] parents,
                                 final int parentIndex, final Genome[] offspring,
                                 final int offspringIndex) {
        final ArrayGenome parent = (ArrayGenome) parents[parentIndex];
        offspring[offspringIndex] = this.owner.getPopulation()
                .getGenomeFactory().factor();
        final ArrayGenome child = (ArrayGenome) offspring[offspringIndex];

        child.copy(parent);

        final int length = parent.size();
        int iswap1 = (int) (rnd.nextDouble() * length);
        int iswap2 = (int) (rnd.nextDouble() * length);

        // can't be equal
        if (iswap1 == iswap2) {
            // move to the next, but
            // don't go out of bounds
            if (iswap1 > 0) {
                iswap1--;
            } else {
                iswap1++;
            }

        }

        // make sure they are in the right order
        if (iswap1 > iswap2) {
            final int temp = iswap1;
            iswap1 = iswap2;
            iswap2 = temp;
        }

        child.swap(iswap1, iswap2);
    }

}