BitChromosomeMultiPointCrossover.java
package net.bmahe.genetics4j.core.combination.multipointcrossover;
import java.util.BitSet;
import java.util.List;
import java.util.random.RandomGenerator;
import org.apache.commons.lang3.Validate;
import net.bmahe.genetics4j.core.chromosomes.BitChromosome;
import net.bmahe.genetics4j.core.chromosomes.Chromosome;
import net.bmahe.genetics4j.core.combination.ChromosomeCombinator;
import net.bmahe.genetics4j.core.spec.AbstractEAConfiguration;
import net.bmahe.genetics4j.core.spec.combination.MultiPointCrossover;
public class BitChromosomeMultiPointCrossover<T extends Comparable<T>> implements ChromosomeCombinator<T> {
private final RandomGenerator randomGenerator;
private final MultiPointCrossover multiPointCrossoverPolicy;
public BitChromosomeMultiPointCrossover(final RandomGenerator _randomGenerator,
final MultiPointCrossover _multiPointCrossoverPolicy) {
Validate.notNull(_randomGenerator);
Validate.notNull(_multiPointCrossoverPolicy);
this.randomGenerator = _randomGenerator;
this.multiPointCrossoverPolicy = _multiPointCrossoverPolicy;
}
@Override
public List<Chromosome> combine(final AbstractEAConfiguration<T> eaConfiguration, final Chromosome chromosome1,
final T firstParentFitness, final Chromosome chromosome2, final T secondParentFitness) {
Validate.notNull(chromosome1);
Validate.notNull(chromosome2);
Validate.isInstanceOf(BitChromosome.class, chromosome1);
Validate.isInstanceOf(BitChromosome.class, chromosome2);
Validate.isTrue(chromosome1.getNumAlleles() == chromosome2.getNumAlleles());
Validate.isTrue(multiPointCrossoverPolicy.numCrossovers() < chromosome1.getNumAlleles());
Validate.isTrue(multiPointCrossoverPolicy.numCrossovers() < chromosome2.getNumAlleles());
final int[] alleleSplits = randomGenerator.ints(0, chromosome1.getNumAlleles())
.distinct()
.limit(multiPointCrossoverPolicy.numCrossovers())
.sorted()
.toArray();
final BitChromosome bitChromosome1 = (BitChromosome) chromosome1;
final BitChromosome bitChromosome2 = (BitChromosome) chromosome2;
final int numAlleles = chromosome1.getNumAlleles();
final BitSet firstChildBitSet = new BitSet(numAlleles);
final BitSet secondChildBitSet = new BitSet(numAlleles);
boolean useChromosome1 = true;
int splitIndex = 0;
for (int i = 0; i < bitChromosome1.getNumAlleles(); i++) {
if (splitIndex < alleleSplits.length && i == alleleSplits[splitIndex]) {
splitIndex++;
useChromosome1 = !useChromosome1;
}
if (useChromosome1) {
firstChildBitSet.set(i, bitChromosome1.getBit(i));
secondChildBitSet.set(i, bitChromosome2.getBit(i));
} else {
firstChildBitSet.set(i, bitChromosome2.getBit(i));
secondChildBitSet.set(i, bitChromosome1.getBit(i));
}
}
return List.of(new BitChromosome(numAlleles, firstChildBitSet), new BitChromosome(numAlleles, secondChildBitSet));
}
}