Splice.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:
 * http://www.heatonresearch.com/copyright
 */
package org.encog.ml.genetic.crossover;

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.ArrayGenome;

/**
 * A simple cross over where genes are simply "spliced". Genes are allowed to
 * repeat.
 */
public class Splice implements EvolutionaryOperator {

	/**
	 * The cut length.
	 */
	private final int cutLength;
	
	/**
	 * The owner.
	 */
	private EvolutionaryAlgorithm owner;

	/**
	 * Create a slice crossover with the specified cut length.
	 * @param theCutLength The cut length.
	 */
	public Splice(final int theCutLength) {
		this.cutLength = theCutLength;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public void performOperation(Random rnd, Genome[] parents, int parentIndex,
			Genome[] offspring, int offspringIndex) {
		
		ArrayGenome mother = (ArrayGenome)parents[parentIndex];
		ArrayGenome father = (ArrayGenome)parents[parentIndex+1];
		ArrayGenome offspring1 = (ArrayGenome)this.owner.getPopulation().getGenomeFactory().factor();
		ArrayGenome offspring2 = (ArrayGenome)this.owner.getPopulation().getGenomeFactory().factor();
		
		offspring[offspringIndex] = offspring1;
		offspring[offspringIndex+1] = offspring2;
		
		final int geneLength = mother.size();

		// the chromosome must be cut at two positions, determine them
		final int cutpoint1 = (int) (rnd.nextInt(geneLength - this.cutLength));
		final int cutpoint2 = cutpoint1 + this.cutLength;

		// handle cut section
		for (int i = 0; i < geneLength; i++) {
			if (!((i < cutpoint1) || (i > cutpoint2))) {
				offspring1.copy(father,i,i);
				offspring2.copy(mother,i,i);
			}
		}

		// handle outer sections
		for (int i = 0; i < geneLength; i++) {
			if ((i < cutpoint1) || (i > cutpoint2)) {
				offspring1.copy(mother,i,i);
				offspring2.copy(father,i,i);
			}
		}
	}

	/**
	 * @return The number of offspring produced, which is 2 for splice crossover.
	 */
	@Override
	public int offspringProduced() {
		return 2;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public int parentsNeeded() {
		return 2;
	}

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