/*
* 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.neural.neat.training.opp.links;
import java.io.Serializable;
import java.util.Random;
import org.encog.ml.ea.train.EvolutionaryAlgorithm;
import org.encog.neural.neat.NEATPopulation;
import org.encog.neural.neat.training.NEATLinkGene;
/**
* Mutate weight links by perturbing their weights. This will be done by adding
* a Gaussian random number with the specified sigma. The sigma specifies the
* standard deviation of the random number. Because the random numbers are
* clustered at zero, this can be either an increase or decrease.
*
* -----------------------------------------------------------------------------
* 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 MutatePerturbLinkWeight implements MutateLinkWeight, Serializable {
/**
* The trainer being used.
*/
private EvolutionaryAlgorithm trainer;
/**
* The sigma (standard deviation) of the Gaussian random numbers.
*/
private final double sigma;
/**
* Construct the perturbing mutator.
*
* @param theSigma
* The sigma (standard deviation) for all random numbers.
*/
public MutatePerturbLinkWeight(final double theSigma) {
this.sigma = theSigma;
}
/**
* {@inheritDoc}
*/
@Override
public EvolutionaryAlgorithm getTrainer() {
return this.trainer;
}
/**
* {@inheritDoc}
*/
@Override
public void init(final EvolutionaryAlgorithm theTrainer) {
this.trainer = theTrainer;
}
/**
* {@inheritDoc}
*/
@Override
public void mutateWeight(final Random rnd, final NEATLinkGene linkGene,
final double weightRange) {
final double delta = rnd.nextGaussian() * this.sigma;
double w = linkGene.getWeight() + delta;
w = NEATPopulation.clampWeight(w, weightRange);
linkGene.setWeight(w);
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
final StringBuilder result = new StringBuilder();
result.append("[");
result.append(this.getClass().getSimpleName());
result.append(":sigma=");
result.append(this.sigma);
result.append("]");
return result.toString();
}
}