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Diffstat (limited to 'src/main/java/org/apache/commons/math/genetics/Chromosome.java')
-rw-r--r-- | src/main/java/org/apache/commons/math/genetics/Chromosome.java | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math/genetics/Chromosome.java b/src/main/java/org/apache/commons/math/genetics/Chromosome.java new file mode 100644 index 0000000..5641a5b --- /dev/null +++ b/src/main/java/org/apache/commons/math/genetics/Chromosome.java @@ -0,0 +1,111 @@ +/* + * 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: 811685 $ $Date: 2009-09-05 19:36:48 +0200 (sam. 05 sept. 2009) $ + */ +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(); + } + } + +} |