io.jenetics.ext.HPRMutator Maven / Gradle / Ivy
/*
* Java Genetic Algorithm Library (jenetics-8.1.0).
* Copyright (c) 2007-2024 Franz Wilhelmstötter
*
* 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.
*
* Author:
* Franz Wilhelmstötter ([email protected])
*/
package io.jenetics.ext;
import java.util.random.RandomGenerator;
import io.jenetics.AbstractAlterer;
import io.jenetics.Chromosome;
import io.jenetics.Gene;
import io.jenetics.Mutator;
import io.jenetics.MutatorResult;
import io.jenetics.internal.math.Probabilities;
import io.jenetics.internal.math.Subsets;
import io.jenetics.util.MSeq;
/**
* The Hybridizing PSM and RSM Operator (HPRM) constructs an offspring from a
* pair of parents by hybridizing two mutation operators, PSM and RSM.
*
* This mutator is described in A New
* Mutation Operator for Solving an NP-Complete Problem: Travelling Salesman
* Problem, by Otman Abdoun, Chakir Tajani and
* Jaafar Abouchabka.
*
* @see RSMutator
* @see io.jenetics.SwapMutator
*
* @author Franz Wilhelmstötter
* @version 5.0
* @since 5.0
*/
public class HPRMutator<
G extends Gene,
C extends Comparable
>
extends Mutator
{
/**
* Constructs an alterer with a given recombination probability.
*
* @param probability the crossover probability.
* @throws IllegalArgumentException if the {@code probability} is not in the
* valid range of {@code [0, 1]}.
*/
public HPRMutator(final double probability) {
super(probability);
}
/**
* Default constructor, with default mutation probability
* ({@link AbstractAlterer#DEFAULT_ALTER_PROBABILITY}).
*/
public HPRMutator() {
this(DEFAULT_ALTER_PROBABILITY);
}
@Override
protected MutatorResult> mutate(
final Chromosome chromosome,
final double p,
final RandomGenerator random
) {
final MutatorResult> result;
if (chromosome.length() > 1) {
final int P = Probabilities.toInt(p);
final int[] points = Subsets.next(random, chromosome.length(), 2);
final MSeq genes = MSeq.of(chromosome);
int mutations = (points[1] - points[0] + 1)/2;
for (int i = points[0], j = points[1]; i < j; ++i, --j) {
genes.swap(i, j);
if (random.nextInt() < P) {
genes.swap(i, random.nextInt(chromosome.length()));
++mutations;
}
}
result = new MutatorResult<>(
chromosome.newInstance(genes.toISeq()),
mutations
);
} else {
result = new MutatorResult<>(chromosome, 0);
}
return result;
}
}