org.jenetics

Class BoltzmannSelector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>

java.lang.Object

org.jenetics.ProbabilitySelector<G,N>

org.jenetics.BoltzmannSelector<G,N>

Type Parameters:

G - the gene type.

N - the BoltzmannSelector requires a number type.

All Implemented Interfaces:

Selector<G,N>

public final class BoltzmannSelector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>
extends ProbabilitySelector<G,N>

In this Selector, the probability for selection is defined as.

where b controls the selection intensity, and

.

f_j denotes the fitness value of the j^th individual.
Positive values of b increases the selection probability of the phenotype with high fitness values. Negative values of b increases the selection probability of phenotypes with low fitness values. If b is zero the selection probability of all phenotypes is set to ¹/_N.

Since:

1.0

Version:

3.2

Author:

Franz Wilhelmstötter

Constructor Summary

Constructors

Constructor and Description
BoltzmannSelector() Create a new BoltzmannSelector with a default beta of 4.0.
BoltzmannSelector(double b) Create a new BoltzmannSelector with the given b value.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj)
int	hashCode()
protected double[]	probabilities(Population<G,N> population, int count) Return an Probability array, which corresponds to the given Population.
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

BoltzmannSelector

public BoltzmannSelector(double b)

Create a new BoltzmannSelector with the given b value. High absolute values of b can create numerical overflows while calculating the selection probabilities.

Parameters:

b - the b value of this BoltzmannSelector

BoltzmannSelector

public BoltzmannSelector()

Create a new BoltzmannSelector with a default beta of 4.0.

Method Detail

probabilities

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

Description copied from class: ProbabilitySelector

Return an Probability array, which corresponds to the given Population. The probability array and the population must have the same size. The population is not sorted. If a subclass needs a sorted population, the subclass is responsible to sort the population.

The implementer always assumes that higher fitness values are better. The base class inverts the probabilities, by reverting the returned probability array, if the GA is supposed to minimize the fitness function.

Specified by:

probabilities in class ProbabilitySelector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>

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