/*
* 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.crossover;
import com.heatonresearch.aifh.AIFHError;
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.IntegerArrayGenome;
import com.heatonresearch.aifh.randomize.GenerateRandom;
import java.util.HashSet;
import java.util.Set;
/**
* A simple cross over where genes are simply "spliced". Genes are not allowed
* to repeat. This method only works with IntegerArrayGenome.
*/
public class SpliceNoRepeat implements EvolutionaryOperator {
/**
* The owner.
*/
private EvolutionaryAlgorithm owner;
/**
* Get a list of the genes that have not been taken before. This is useful
* if you do not wish the same gene to appear more than once in a
* genome.
*
* @param source The pool of genes to select from.
* @param taken An array of the taken genes.
* @return Those genes in source that are not taken.
*/
private static int getNotTaken(final IntegerArrayGenome source,
final Set<Integer> taken) {
for (final int trial : source.getData()) {
if (!taken.contains(trial)) {
taken.add(trial);
return trial;
}
}
throw new AIFHError("Ran out of integers to select.");
}
/**
* The cut length.
*/
private int cutLength;
/**
* Construct a splice crossover.
*
* @param theCutLength The cut length.
*/
public SpliceNoRepeat(final int theCutLength) {
this.cutLength = theCutLength;
}
/**
* {@inheritDoc}
*/
@Override
public void performOperation(GenerateRandom rnd, Genome[] parents, int parentIndex,
Genome[] offspring, int offspringIndex) {
IntegerArrayGenome mother = (IntegerArrayGenome) parents[parentIndex];
IntegerArrayGenome father = (IntegerArrayGenome) parents[parentIndex + 1];
IntegerArrayGenome offspring1 = (IntegerArrayGenome) this.owner.getPopulation().getGenomeFactory().factor();
IntegerArrayGenome offspring2 = (IntegerArrayGenome) 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 = rnd.nextInt(geneLength - this.cutLength);
final int cutpoint2 = cutpoint1 + this.cutLength;
// keep track of which genes have been taken in each of the two
// offspring, defaults to false.
final Set<Integer> taken1 = new HashSet<Integer>();
final Set<Integer> taken2 = new HashSet<Integer>();
// 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);
taken1.add(father.getData()[i]);
taken2.add(mother.getData()[i]);
}
}
// handle outer sections
for (int i = 0; i < geneLength; i++) {
if ((i < cutpoint1) || (i > cutpoint2)) {
offspring1.getData()[i] = SpliceNoRepeat.getNotTaken(mother, taken1);
offspring2.getData()[i] = SpliceNoRepeat.getNotTaken(father, taken2);
}
}
}
/**
* @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;
}
}