org.jenetics

Class TruncationSelector<G extends Gene<?,G>,C extends Comparable<? super C>>

java.lang.Object

org.jenetics.TruncationSelector<G,C>

All Implemented Interfaces:

Selector<G,C>

public final class TruncationSelector<G extends Gene<?,G>,C extends Comparable<? super C>>
extends Object
implements Selector<G,C>

In truncation selection individuals are sorted according to their fitness. Only the n best individuals are selected. The truncation selection is a very basic selection algorithm. It has it's strength in fast selecting individuals in large populations, but is not very often used in practice.

Since:

1.0

Version:

3.8

Author:

Franz Wilhelmstötter

See Also:

Wikipedia: Truncation selection

Constructor Summary

Constructors

Constructor and Description
TruncationSelector() Create a new TruncationSelector object.
TruncationSelector(int n) Create a new TruncationSelector object, where the worst selected individual has rank n.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj)
int	hashCode()
Population<G,C>	select(Population<G,C> population, int count, Optimize opt) This method sorts the population in descending order while calculating the selection probabilities.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

TruncationSelector

public TruncationSelector(int n)

Create a new TruncationSelector object, where the worst selected individual has rank n. This means, if you want to select count individuals, the worst selected individual has rank n. If count > n, the selected population will contain duplicate individuals.

Parameters:

n - the worst rank of the selected individuals

Throws:

IllegalArgumentException - if n < 1

Since:

3.8

TruncationSelector

public TruncationSelector()

Create a new TruncationSelector object.

Method Detail

select

public Population<G,C> select(Population<G,C> population,
                              int count,
                              Optimize opt)

This method sorts the population in descending order while calculating the selection probabilities. (The method Population.sortWith(java.util.Comparator) )} is called by this method.) If the selection size is greater the the population size, the whole population is duplicated until the desired sample size is reached.

Specified by:

select in interface Selector<G extends Gene<?,G>,C extends Comparable<? super C>>

Parameters:

population - The population to select from.

count - The number of phenotypes to select.

opt - Determines whether the individuals with higher fitness values or lower fitness values must be selected. This parameter determines whether the GA maximizes or minimizes the fitness function.

Returns:

The selected phenotypes (a new Population).

Throws:

NullPointerException - if the population or opt is null.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object