/* * 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; /** * Individual in a population. Chromosomes are compared based on their fitness. * *
The chromosomes are IMMUTABLE, and so their fitness is also immutable and therefore it can be
* cached.
*
* @since 2.0
*/
public abstract class Chromosome implements Comparable Computation of fitness is usually very time-consuming task, therefore the fitness is
* cached.
*
* @return the fitness
*/
public double getFitness() {
if (this.fitness == NO_FITNESS) {
// no cache - compute the fitness
this.fitness = fitness();
}
return this.fitness;
}
/**
* Compares two chromosomes based on their fitness. The bigger the fitness, the better the
* chromosome.
*
* @param another another chromosome to compare
* @return
*
*
*/
public int compareTo(final Chromosome another) {
return Double.compare(getFitness(), another.getFitness());
}
/**
* Returns another
is better than this
* another
is worse than this
* true
iff another
has the same representation and therefore
* the same fitness. By default, it returns false -- override it in your implementation if you
* need it.
*
* @param another chromosome to compare
* @return true if another
is equivalent to this chromosome
*/
protected boolean isSame(final Chromosome another) {
return false;
}
/**
* Searches the population
for another chromosome with the same representation. If
* such chromosome is found, it is returned, if no such chromosome exists, returns null
*
.
*
* @param population Population to search
* @return Chromosome with the same representation, or null
if no such chromosome
* exists.
*/
protected Chromosome findSameChromosome(final Population population) {
for (Chromosome anotherChr : population) {
if (this.isSame(anotherChr)) {
return anotherChr;
}
}
return null;
}
/**
* Searches the population for a chromosome representing the same solution, and if it finds one,
* updates the fitness to its value.
*
* @param population Population to search
*/
public void searchForFitnessUpdate(final Population population) {
Chromosome sameChromosome = findSameChromosome(population);
if (sameChromosome != null) {
fitness = sameChromosome.getFitness();
}
}
}