/*
* Encog(tm) Core v3.3 - Java Version
* http://www.heatonresearch.com/encog/
* https://github.com/encog/encog-java-core
* Copyright 2008-2014 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.neural.neat.training.opp;
import java.util.Random;
import org.encog.mathutil.randomize.RangeRandomizer;
import org.encog.ml.ea.genome.Genome;
import org.encog.neural.neat.training.NEATGenome;
import org.encog.neural.neat.training.NEATLinkGene;
/**
* Mutate a genome by removing a random link. Do not remove links from genomes
* that have fewer than 5 links.
*
* -----------------------------------------------------------------------------
* http://www.cs.ucf.edu/~kstanley/ Encog's NEAT implementation was drawn from
* the following three Journal Articles. For more complete BibTeX sources, see
* NEATNetwork.java.
*
* Evolving Neural Networks Through Augmenting Topologies
*
* Generating Large-Scale Neural Networks Through Discovering Geometric
* Regularities
*
* Automatic feature selection in neuroevolution
*/
public class NEATMutateRemoveLink extends NEATMutation {
/**
* Do not remove from genomes that have fewer than this number of links.
*/
public static final int MIN_LINK = 5;
/**
* {@inheritDoc}
*/
@Override
public void performOperation(final Random rnd, final Genome[] parents,
final int parentIndex, final Genome[] offspring,
final int offspringIndex) {
final NEATGenome target = obtainGenome(parents, parentIndex, offspring,
offspringIndex);
if (target.getLinksChromosome().size() < NEATMutateRemoveLink.MIN_LINK) {
// don't remove from small genomes
return;
}
// determine the target and remove
final int index = RangeRandomizer.randomInt(0, target
.getLinksChromosome().size() - 1);
final NEATLinkGene targetGene = target.getLinksChromosome().get(index);
target.getLinksChromosome().remove(index);
// if this orphaned any nodes, then kill them too!
if (!isNeuronNeeded(target, targetGene.getFromNeuronID())) {
removeNeuron(target, targetGene.getFromNeuronID());
}
if (!isNeuronNeeded(target, targetGene.getToNeuronID())) {
removeNeuron(target, targetGene.getToNeuronID());
}
}
}