/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ package org.apache.commons.math3.genetics; import org.apache.commons.math3.exception.DimensionMismatchException; import org.apache.commons.math3.exception.MathIllegalArgumentException; import org.apache.commons.math3.exception.NotStrictlyPositiveException; import org.apache.commons.math3.exception.NumberIsTooLargeException; import org.apache.commons.math3.exception.util.LocalizedFormats; import org.apache.commons.math3.random.RandomGenerator; import java.util.ArrayList; import java.util.List; /** * N-point crossover policy. For each iteration a random crossover point is selected and the first * part from each parent is copied to the corresponding child, and the second parts are copied * crosswise. * *
Example (2-point crossover): * *
* -C- denotes a crossover point * -C- -C- -C- -C- * p1 = (1 0 | 1 0 0 1 | 0 1 1) X p2 = (0 1 | 1 0 1 0 | 1 1 1) * \----/ \-------/ \-----/ \----/ \--------/ \-----/ * || (*) || || (**) || * VV (**) VV VV (*) VV * /----\ /--------\ /-----\ /----\ /--------\ /-----\ * c1 = (1 0 | 1 0 1 0 | 0 1 1) X c2 = (0 1 | 1 0 0 1 | 0 1 1) ** * This policy works only on {@link AbstractListChromosome}, and therefore it is parameterized by T. * Moreover, the chromosomes must have same lengths. * * @param
Note: the number of crossover points must be < chromosome length - 1
*
. This condition can only be checked at runtime, as the chromosome length is not known
* in advance.
*
* @param crossoverPoints the number of crossover points
* @throws NotStrictlyPositiveException if the number of {@code crossoverPoints} is not strictly
* positive
*/
public NPointCrossover(final int crossoverPoints) throws NotStrictlyPositiveException {
if (crossoverPoints <= 0) {
throw new NotStrictlyPositiveException(crossoverPoints);
}
this.crossoverPoints = crossoverPoints;
}
/**
* Returns the number of crossover points used by this {@link CrossoverPolicy}.
*
* @return the number of crossover points
*/
public int getCrossoverPoints() {
return crossoverPoints;
}
/**
* Performs a N-point crossover. N random crossover points are selected and are used to divide
* the parent chromosomes into segments. The segments are copied in alternate order from the two
* parents to the corresponding child chromosomes.
*
*
Example (2-point crossover): * *
* -C- denotes a crossover point * -C- -C- -C- -C- * p1 = (1 0 | 1 0 0 1 | 0 1 1) X p2 = (0 1 | 1 0 1 0 | 1 1 1) * \----/ \-------/ \-----/ \----/ \--------/ \-----/ * || (*) || || (**) || * VV (**) VV VV (*) VV * /----\ /--------\ /-----\ /----\ /--------\ /-----\ * c1 = (1 0 | 1 0 1 0 | 0 1 1) X c2 = (0 1 | 1 0 0 1 | 0 1 1) ** * @param first first parent (p1) * @param second second parent (p2) * @return pair of two children (c1,c2) * @throws MathIllegalArgumentException iff one of the chromosomes is not an instance of {@link * AbstractListChromosome} * @throws DimensionMismatchException if the length of the two chromosomes is different */ @SuppressWarnings("unchecked") // OK because of instanceof checks public ChromosomePair crossover(final Chromosome first, final Chromosome second) throws DimensionMismatchException, MathIllegalArgumentException { if (!(first instanceof AbstractListChromosome> && second instanceof AbstractListChromosome>)) { throw new MathIllegalArgumentException( LocalizedFormats.INVALID_FIXED_LENGTH_CHROMOSOME); } return mate((AbstractListChromosome