org.apache.commons.math3.genetics
Class UniformCrossover<T>

java.lang.Object
  extended by org.apache.commons.math3.genetics.UniformCrossover<T>
Type Parameters:
T - generic type of the AbstractListChromosomes for crossover
All Implemented Interfaces:
CrossoverPolicy

public class UniformCrossover<T>
extends Object
implements CrossoverPolicy

Perform Uniform Crossover [UX] on the specified chromosomes. A fixed mixing ratio is used to combine genes from the first and second parents, e.g. using a ratio of 0.5 would result in approximately 50% of genes coming from each parent. This is typically a poor method of crossover, but empirical evidence suggests that it is more exploratory and results in a larger part of the problem space being searched.

This crossover policy evaluates each gene of the parent chromosomes by chosing a uniform random number p in the range [0, 1]. If p < ratio, the parent genes are swapped. This means with a ratio of 0.7, 30% of the genes from the first parent and 70% from the second parent will be selected for the first offspring (and vice versa for the second offspring).

This policy works only on AbstractListChromosome, and therefore it is parameterized by T. Moreover, the chromosomes must have same lengths.

Since:
3.1
Version:
$Id: UniformCrossover.java 1385297 2012-09-16 16:05:57Z tn $
See Also:
Crossover techniques (Wikipedia), Crossover (Obitko.com), Uniform crossover

Constructor Summary
UniformCrossover(double ratio)
          Creates a new UniformCrossover policy using the given mixing ratio.
 
Method Summary
 ChromosomePair crossover(Chromosome first, Chromosome second)
          Perform a crossover operation on the given chromosomes.
 double getRatio()
          Returns the mixing ratio used by this CrossoverPolicy.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

UniformCrossover

public UniformCrossover(double ratio)
                 throws OutOfRangeException
Creates a new UniformCrossover policy using the given mixing ratio.

Parameters:
ratio - the mixing ratio
Throws:
OutOfRangeException - if the mixing ratio is outside the [0, 1] range
Method Detail

getRatio

public double getRatio()
Returns the mixing ratio used by this CrossoverPolicy.

Returns:
the mixing ratio

crossover

public ChromosomePair crossover(Chromosome first,
                                Chromosome second)
                         throws DimensionMismatchException,
                                MathIllegalArgumentException
Perform a crossover operation on the given chromosomes.

Specified by:
crossover in interface CrossoverPolicy
Parameters:
first - the first chromosome.
second - the second chromosome.
Returns:
the pair of new chromosomes that resulted from the crossover.
Throws:
MathIllegalArgumentException - iff one of the chromosomes is not an instance of AbstractListChromosome
DimensionMismatchException - if the length of the two chromosomes is different


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