1 package net.bmahe.genetics4j.core.mutation.chromosome.swapmutation;
2
3 import java.util.BitSet;
4 import java.util.Objects;
5 import java.util.random.RandomGenerator;
6
7 import org.apache.commons.lang3.Validate;
8
9 import net.bmahe.genetics4j.core.chromosomes.BitChromosome;
10 import net.bmahe.genetics4j.core.chromosomes.Chromosome;
11 import net.bmahe.genetics4j.core.mutation.chromosome.ChromosomeMutationHandler;
12 import net.bmahe.genetics4j.core.spec.chromosome.BitChromosomeSpec;
13 import net.bmahe.genetics4j.core.spec.chromosome.ChromosomeSpec;
14 import net.bmahe.genetics4j.core.spec.mutation.MutationPolicy;
15 import net.bmahe.genetics4j.core.spec.mutation.SwapMutation;
16
17 public class BitChromosomeSwapMutationHandler implements ChromosomeMutationHandler<BitChromosome> {
18
19 private final RandomGenerator randomGenerator;
20
21 public BitChromosomeSwapMutationHandler(final RandomGenerator _randomGenerator) {
22 Objects.requireNonNull(_randomGenerator);
23
24 this.randomGenerator = _randomGenerator;
25 }
26
27 @Override
28 public boolean canHandle(final MutationPolicy mutationPolicy, final ChromosomeSpec chromosome) {
29 Objects.requireNonNull(mutationPolicy);
30 Objects.requireNonNull(chromosome);
31
32 return mutationPolicy instanceof SwapMutation && chromosome instanceof BitChromosomeSpec;
33 }
34
35 @Override
36 public BitChromosome mutate(final MutationPolicy mutationPolicy, final Chromosome chromosome) {
37 Objects.requireNonNull(mutationPolicy);
38 Objects.requireNonNull(chromosome);
39 Validate.isInstanceOf(SwapMutation.class, mutationPolicy);
40 Validate.isInstanceOf(BitChromosome.class, chromosome);
41
42 final SwapMutation swapMutation = (SwapMutation) mutationPolicy;
43 final int numSwap = swapMutation.isNumSwapFixed() ? swapMutation.numSwap()
44 : 1 + randomGenerator.nextInt(swapMutation.numSwap());
45
46 final BitChromosome bitChromosome = (BitChromosome) chromosome;
47
48 final BitSet newBitSet = new BitSet(bitChromosome.getNumAlleles());
49 for (int i = 0; i < bitChromosome.getNumAlleles(); i++) {
50 newBitSet.or(bitChromosome.getBitSet());
51 }
52
53 for (int i = 0; i < numSwap; i++) {
54 final int value1Index = randomGenerator.nextInt(bitChromosome.getNumAlleles());
55 final int value2Index = randomGenerator.nextInt(bitChromosome.getNumAlleles());
56
57 final boolean value1 = newBitSet.get(value1Index);
58 final boolean value2 = newBitSet.get(value2Index);
59
60 newBitSet.set(value1Index, value2);
61 newBitSet.set(value2Index, value1);
62 }
63 return new BitChromosome(bitChromosome.getNumAlleles(), newBitSet);
64 }
65 }