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Eliminated the "mutation requirement" in nextGeneration method. 

Added algorithm description in javadoc.
JIRA: MATH-207
Reported and patched by David Stefka




git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/branches/MATH_2_0@699704 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Phil Steitz 2008-09-27 18:05:19 +00:00
parent dbd8ffb54f
commit 6460cd272a
1 changed files with 35 additions and 11 deletions
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46
src/java/org/apache/commons/math/genetics/GeneticAlgorithm.java
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@ -19,6 +19,7 @@ package org.apache.commons.math.genetics;
/**
* Implementation of a genetic algorithm. All factors that govern the operation
* of the algorithm can be configured for a specific problem.
*
* @version $Revision$ $Date$
*/
public class GeneticAlgorithm {
@ -99,7 +100,24 @@ public class GeneticAlgorithm {
}
/**
* Evolve the given population into the next generation.
* <p>Evolve the given population into the next generation.</p>
* <p><ol>
* <li>Get nextGeneration polulation to fill from <code>current</code>
* generation, using its nextGeneration method</li>
* <li>Loop until new generation is filled:</li>
* <ul><li>Apply configured SelectionPolicy to select a pair of parents
* from <code>current</code></li>
* <li>With probability = {@link #getCrossoverRate()}, apply
* configured {@link CrossoverPolicy} to parents</li>
* <li>With probability = {@link #getMutationRate()}, apply
* configured {@link MutationPolicy} to each parent</li>
* <li>Add resulting chromosomes individually to nextGeneration,
* space permitting</li>
* </ul>
* <li>Return nextGeneration</li>
* </ol>
* </p>
*
*
* @param current the current population.
* @return the population for the next generation.
@ -112,23 +130,29 @@ public class GeneticAlgorithm {
// select parent chromosomes
ChromosomePair pair = getSelectionPolicy().select(current);
// apply crossover policy to create two offspring
// crossover?
if (Math.random() < getCrossoverRate()) {
// apply crossover policy to create two offspring
pair = getCrossoverPolicy().crossover(pair.getFirst(),
pair.getSecond());
}
// apply mutation policy to first offspring
// mutation?
if (Math.random() < getMutationRate()) {
nextGeneration.addChromosome(getMutationPolicy().mutate(
pair.getFirst()));
// apply mutation policy to the chromosomes
pair = new ChromosomePair(
getMutationPolicy().mutate(pair.getFirst()),
getMutationPolicy().mutate(pair.getSecond())
);
}
if (nextGeneration.getPopulationSize() < nextGeneration
.getPopulationLimit()) {
// apply mutation policy to second offspring
nextGeneration.addChromosome(getMutationPolicy().mutate(
pair.getSecond()));
}
// add the first chromosome to the population
nextGeneration.addChromosome(pair.getFirst());
// is there still a place for the second chromosome?
if (nextGeneration.getPopulationSize() < nextGeneration
.getPopulationLimit()) {
// add the second chromosome to the population
nextGeneration.addChromosome(pair.getSecond());
}
}