org.apache.commons.math3.genetics

Class TournamentSelection

java.lang.Object

org.apache.commons.math3.genetics.TournamentSelection

All Implemented Interfaces:

SelectionPolicy

public class TournamentSelection
extends java.lang.Object
implements SelectionPolicy

Tournament selection scheme. Each of the two selected chromosomes is selected based on n-ary tournament -- this is done by drawing arity random chromosomes without replacement from the population, and then selecting the fittest chromosome among them.

Since:

2.0

Field Summary

Fields

Modifier and Type	Field and Description
private int	arity number of chromosomes included in the tournament selections

Constructor Summary

Constructors

Constructor and Description
TournamentSelection(int arity) Creates a new TournamentSelection instance.

Method Summary

Methods

Modifier and Type	Method and Description
int	getArity() Gets the arity (number of chromosomes drawn to the tournament).
ChromosomePair	select(Population population) Select two chromosomes from the population.
void	setArity(int arity) Sets the arity (number of chromosomes drawn to the tournament).
private Chromosome	tournament(ListPopulation population) Helper for select(Population).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

arity

private int arity

number of chromosomes included in the tournament selections

Constructor Detail

TournamentSelection

public TournamentSelection(int arity)

Creates a new TournamentSelection instance.

Parameters:

arity - how many chromosomes will be drawn to the tournament

Method Detail

select

public ChromosomePair select(Population population)
                      throws MathIllegalArgumentException

Select two chromosomes from the population. Each of the two selected chromosomes is selected based on n-ary tournament -- this is done by drawing arity random chromosomes without replacement from the population, and then selecting the fittest chromosome among them.

Specified by:

select in interface SelectionPolicy

Parameters:

population - the population from which the chromosomes are chosen.

Returns:

the selected chromosomes.

Throws:

MathIllegalArgumentException - if the tournament arity is bigger than the population size

tournament

private Chromosome tournament(ListPopulation population)
                       throws MathIllegalArgumentException

Helper for select(Population). Draw arity random chromosomes without replacement from the population, and then select the fittest chromosome among them.

Parameters:

population - the population from which the chromosomes are chosen.

Returns:

the selected chromosome.

Throws:

MathIllegalArgumentException - if the tournament arity is bigger than the population size

getArity

public int getArity()

Gets the arity (number of chromosomes drawn to the tournament).

Returns:

arity of the tournament

setArity

public void setArity(int arity)

Sets the arity (number of chromosomes drawn to the tournament).

Parameters:

arity - arity of the tournament