org.jenetics

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

java.lang.Object

org.jenetics.ProbabilitySelector<G,N>

org.jenetics.RouletteWheelSelector<G,N>

org.jenetics.StochasticUniversalSelector<G,N>

All Implemented Interfaces:

Selector<G,N>

public class StochasticUniversalSelector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>
extends RouletteWheelSelector<G,N>

StochasticUniversalSelector is a method for selecting a population according to some given probability in a way that minimize chance fluctuations. It can be viewed as a type of roulette game where now we have P equally spaced points which we spin.

The figure above shows how the stochastic-universal selection works; n is the number of individuals to select.

Since:

1.0

Version:

2.0 — $Date: 2014-12-28 $

Author:

Franz Wilhelmstötter

See Also:

Wikipedia: Stochastic universal sampling

Constructor Summary

Constructors

Constructor and Description
StochasticUniversalSelector()

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.
Population<G,N>	select(Population<G,N> population, int count, Optimize opt) This method sorts the population in descending order while calculating the selection probabilities.
String	toString()

Methods inherited from class org.jenetics.ProbabilitySelector

probabilities

Methods inherited from class java.lang.Object

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

Constructor Detail

StochasticUniversalSelector

public StochasticUniversalSelector()

Method Detail

select

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

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

Specified by:

select in interface Selector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>

Overrides:

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

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).

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 (p = 1.0 - p ) if the GA is supposed to minimize the fitness function.

Overrides:

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

equals

public boolean equals(Object obj)

Overrides:

equals in class RouletteWheelSelector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>

toString

public String toString()

Overrides:

toString in class RouletteWheelSelector<G extends Gene<?,G>,N extends Number & Comparable<? super N>>