Author: psteitz
Date: Sat Sep 27 11:05:19 2008
New Revision: 699704
URL: http://svn.apache.org/viewvc?rev=699704&view=rev
Log:
Eliminated the "mutation requirement" in nextGeneration method.
Added algorithm description in javadoc.
JIRA: MATH-207
Reported and patched by David Stefka
Modified:
commons/proper/math/branches/MATH_2_0/src/java/org/apache/commons/math/genetics/GeneticAlgorithm.java
Modified:
commons/proper/math/branches/MATH_2_0/src/java/org/apache/commons/math/genetics/GeneticAlgorithm.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/branches/MATH_2_0/src/java/org/apache/commons/math/genetics/GeneticAlgorithm.java?rev=699704&r1=699703&r2=699704&view=diff
==============================================================================
---
commons/proper/math/branches/MATH_2_0/src/java/org/apache/commons/math/genetics/GeneticAlgorithm.java
(original)
+++
commons/proper/math/branches/MATH_2_0/src/java/org/apache/commons/math/genetics/GeneticAlgorithm.java
Sat Sep 27 11:05:19 2008
@@ -19,6 +19,7 @@
/**
* 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 @@
}
/**
- * 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 = [EMAIL PROTECTED] #getCrossoverRate()},
apply
+ * configured [EMAIL PROTECTED] CrossoverPolicy} to parents</li>
+ * <li>With probability = [EMAIL PROTECTED] #getMutationRate()},
apply
+ * configured [EMAIL PROTECTED] 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 @@
// 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());
}
}
