| /* |
| * 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.math.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 |
| * @version $Revision:$ $Date:$ |
| */ |
| public abstract class Chromosome implements Comparable<Chromosome>,Fitness { |
| |
| /** |
| * Cached value of the fitness of this chromosome. |
| */ |
| private double fitness = Double.MIN_VALUE; |
| |
| /** |
| * Access the fitness of this chromosome. The bigger the fitness, the better |
| * the chromosome. |
| * |
| * Computation of fitness is usually very time-consuming task, therefore the |
| * fitness is cached. |
| * |
| * @return the fitness. |
| */ |
| public double getFitness() { |
| if (this.fitness == Double.MIN_VALUE) { |
| // 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 |
| * <ul> |
| * <li>-1 if <code>another</code> is better than <code>this</code></li> |
| * <li>1 if <code>another</code> is worse than <code>this</code></li> |
| * <li>0 if the two chromosomes have the same fitness</li> |
| * </ul> |
| */ |
| public int compareTo(Chromosome another) { |
| return ((Double)this.getFitness()).compareTo(another.getFitness()); |
| } |
| |
| /** |
| * Returns <code>true<code> iff <code>another</code> 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 <code>another</code> is equivalent to this chromosome |
| */ |
| protected boolean isSame(Chromosome another) { |
| return false; |
| } |
| |
| /** |
| * Searches the <code>population</code> for another chromosome with the same |
| * representation. If such chromosome is found, it is returned, if no such |
| * chromosome exists, returns <code>null</code>. |
| * |
| * @param population |
| * Population to search |
| * @return Chromosome with the same representation, or <code>null</code> if |
| * no such chromosome exists. |
| */ |
| protected Chromosome findSameChromosome(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(Population population) { |
| Chromosome sameChromosome = findSameChromosome(population); |
| if (sameChromosome != null) { |
| fitness = sameChromosome.getFitness(); |
| } |
| } |
| |
| } |