MutatePerturb.java

/*
 * Encog(tm) Core v3.4 - Java Version
 * http://www.heatonresearch.com/encog/
 * https://github.com/encog/encog-java-core
 
 * Copyright 2008-2016 Heaton Research, Inc.
 *
 * 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:
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 */
package org.encog.ml.genetic.mutate;

import java.util.Random;

import org.encog.ml.ea.genome.Genome;
import org.encog.ml.ea.opp.EvolutionaryOperator;
import org.encog.ml.ea.train.EvolutionaryAlgorithm;
import org.encog.ml.genetic.genome.DoubleArrayGenome;

/**
 * A simple mutation based on random numbers.
 */
public class MutatePerturb implements EvolutionaryOperator {

	/**
	 * The amount to perturb by.
	 */
	private final double perturbAmount;

	/**
	 * Construct a perturb mutation.
	 * @param thePerturbAmount The amount to mutate by(percent).
	 */
	public MutatePerturb(final double thePerturbAmount) {
		this.perturbAmount = thePerturbAmount;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void performOperation(Random rnd, Genome[] parents, int parentIndex,
			Genome[] offspring, int offspringIndex) {
		DoubleArrayGenome parent = (DoubleArrayGenome)parents[parentIndex];
		offspring[offspringIndex] = parent.getPopulation().getGenomeFactory().factor();
		DoubleArrayGenome child = (DoubleArrayGenome)offspring[offspringIndex];
		
		for(int i=0;i<parent.size();i++) {
			double value = parent.getData()[i];
			value += value * (perturbAmount - (rnd.nextDouble() * perturbAmount * 2));
			child.getData()[i] = value;
		}
	}
	
	/**
	 * @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 init(EvolutionaryAlgorithm theOwner) {
		// not needed
	}
}