jenes.stage.operator

Class Selector<T extends Chromosome>

java.lang.Object

jenes.stage.AbstractStage<T>

jenes.stage.operator.Operator<T>

jenes.stage.operator.Selector<T>

Type Parameters:

T - The class of chromosomes to work with.

Direct Known Subclasses:

RouletteWheelSelector, TournamentSelector

public abstract class Selector<T extends Chromosome>
extends Operator<T>

A class representing a generic selection operator.

The actual selector is implemented by subclassing this abstract class and providing the select(Population) and Selector#preSelect(Population) method implementations: the former is required to select individuals from the specified Population; the latter is required to set up the selector state when a new selection begins.

A maxIllegalRate is specified to obtain a population with a max number of illegal individuals selected. When this threshould is reached, the new illegal selected individuals are not added at the output population, and the selection process is repeated.

At the start selection time the output population has already the individuals; the individuals selected from the input population have not to be added at the output population: each output population individual is set as the one selected by the input population.

The output population size will be equal to the input population one; automatically new individuals are added or old ones are deleted to make the sizes equal.

A Selector.Statistics is associated to each selector operator.

Since:

1.0

Version:

2.0

See Also:

Individual, Population

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	Selector.Statistics A statistics object holding the number of selection performed and the time spent to execute them.

Field Summary

Fields

Modifier and Type	Field and Description
static double	DEFAULT_MAX_ILLEGAL_RATE The default percentage of allowed illegal individuals

Fields inherited from class jenes.stage.operator.Operator

random, statistics

Fields inherited from class jenes.stage.AbstractStage

biggerIsBetter, fitness, ga

Constructor Summary

Constructors

Constructor and Description
Selector() Constructs a new Selector operator.
Selector(int n) Constructs a new Selector operator, specifying the number of individuals to select.

Method Summary

Methods

Modifier and Type	Method and Description
double	getMaxIllegalRate() Returns the max number of illegal individuals this selector operator can select.
int	getSelectionRate() Returns the number of individuals selected by this operator.
void	init(GeneticAlgorithm<T> ga) Initializes this stage according to the genetic algorithm that uses it
protected void	preSelect(Population<T> pop, Population.Filter filter) Sets up the selection state according a population's state.
void	process(Population<T> in, Population<T> out) Sets the individuals in the output population like the selected ones
protected abstract Individual<T>	select(java.util.List<Individual<T>> pop) Selects an individual in the filtered population
Individual<T>	select(Population<T> pop) Selects an individual in the population
void	setMaxIllegalRate(double rate) Sets the max number of illegal individuals this selector operator can select.
void	setSelectionRate(int n) Sets the number of individuals being selected by this operator.

Methods inherited from class jenes.stage.operator.Operator

getStatistics, updateStatistics

Methods inherited from class jenes.stage.AbstractStage

dispose, getFitness, isBiggerBetter, isFitnessChanged, setBiggerIsBetter, setBiggerIsBetter, setFitness, setFitness

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_ILLEGAL_RATE

public static final double DEFAULT_MAX_ILLEGAL_RATE

The default percentage of allowed illegal individuals

See Also:

Constant Field Values

Constructor Detail

Selector

public Selector()

Constructs a new Selector operator.

Selector

public Selector(int n)

Constructs a new Selector operator, specifying the number of individuals to select.

Parameters:

n - the number of individuals to select

Method Detail

getMaxIllegalRate

public final double getMaxIllegalRate()

Returns the max number of illegal individuals this selector operator can select.

Returns:

the max illegal rate

setMaxIllegalRate

public void setMaxIllegalRate(double rate)

Sets the max number of illegal individuals this selector operator can select.

Parameters:

rate - the max illegal rate

getSelectionRate

public final int getSelectionRate()

Returns the number of individuals selected by this operator.

Returns:

the number of individuals selected.

setSelectionRate

public void setSelectionRate(int n)

Sets the number of individuals being selected by this operator. If the given number is zero or negative, then it is set to -1, meaning that a number equal to to the input population will be selected.

Parameters:

n - the number of individuals being selected.

init

public void init(GeneticAlgorithm<T> ga)

Description copied from class: AbstractStage

Initializes this stage according to the genetic algorithm that uses it

Overrides:

init in class AbstractStage<T extends Chromosome>

Parameters:

ga - the Genetic Algorithm in wchic this stage run

process

public final void process(Population<T> in,
           Population<T> out)
                   throws StageException

Sets the individuals in the output population like the selected ones

Specified by:

process in class AbstractStage<T extends Chromosome>

Parameters:

in - the input population

out - the output population

Throws:

StageException

preSelect

protected void preSelect(Population<T> pop,
             Population.Filter filter)

Sets up the selection state according a population's state. It is invoked at the beginning of selection for the specified (filtered) population.

Parameters:

pop - the population to process by the stage

filter -

select

protected abstract Individual<T> select(java.util.List<Individual<T>> pop)

Selects an individual in the filtered population

Parameters:

pop - from which to choose an individual.

Returns:

the individual selected

select

public final Individual<T> select(Population<T> pop)

Selects an individual in the population

Parameters:

pop -

Returns: