org.jenetics

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

java.lang.Object

org.jenetics.ProbabilitySelector<G,C>

org.jenetics.ExponentialRankSelector<G,C>

All Implemented Interfaces:

Selector<G,C>

public final class ExponentialRankSelector<G extends Gene<?,G>,C extends Comparable<? super C>>
extends ProbabilitySelector<G,C>

An alternative to the "weak" LinearRankSelector is to assign survival probabilities to the sorted individuals using an exponential function.

,

where c must within the range [0..1).

A small value of c increases the probability of the best phenotypes to be selected. If c is set to zero, the selection probability of the best phenotype is set to one. The selection probability of all other phenotypes is zero. A value near one equalizes the selection probabilities.

This selector sorts the population in descending order while calculating the selection probabilities.

Since:

1.0

Version:

2.0

Author:

Franz Wilhelmstötter

Constructor Summary

Constructors

Constructor and Description
ExponentialRankSelector() Create a new selector with default value of 0.975.
ExponentialRankSelector(double c) Create a new exponential rank selector.

Method Summary

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

Methods inherited from class org.jenetics.ProbabilitySelector

probabilities, select

Methods inherited from class java.lang.Object

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

Constructor Detail

ExponentialRankSelector

public ExponentialRankSelector(double c)

Create a new exponential rank selector.

Parameters:

c - the c value.

Throws:

IllegalArgumentException - if c is not within the range [0..1).

ExponentialRankSelector

public ExponentialRankSelector()

Create a new selector with default value of 0.975.

Method Detail

probabilities

protected double[] probabilities(Population<G,C> population,
                                 int count)

This method sorts the population in descending order while calculating the selection probabilities. (The method Population.populationSort() is called by this method.)

Specified by:

probabilities in class ProbabilitySelector<G extends Gene<?,G>,C extends Comparable<? super C>>

Parameters:

population - The unsorted population.

count - The number of phenotypes to select. This parameter is not needed for most implementations.

Returns:

Probability array. The returned probability array must have the length population.size() and must sum to one. The returned value is checked with assert(Math.abs(math.sum(probabilities) - 1.0) < 0.0001) in the base class.

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