ec.select

Class BestSelection

java.lang.Object

ec.BreedingSource

ec.SelectionMethod

ec.select.BestSelection

All Implemented Interfaces:

Prototype, Setup, RandomChoiceChooserD, Serializable, Cloneable

public class BestSelection
extends SelectionMethod

Performs a tournament selection restricted to only the best, or worst, n indivdiuals in the population. If the best individuals, then tournament selection will prefer the better among them; if the worst individuals, then tournament selection will prefer the worse among them. The procedure for performing restriction is expensive to set up and bring down, so it's not appropriate for steady-state evolution. Like TournamentSelection, the size of the tournament can be any If you're not familiar with the relative advantages of selection methods and just want a good one, use TournamentSelection instead. Not appropriate for multiobjective fitnesses.

The tournament size can be any floating point value >= 1.0. If it is a non- integer value x then either a tournament of size ceil(x) is used (with probability x - floor(x)), else a tournament of size floor(x) is used.

Typical Number of Individuals Produced Per produce(...) call
Always 1.

Parameters

base.pick-worst bool = true or false (default)	(should we pick from among the worst n individuals in the tournament instead of the best n?)
base.size double >= 1	(the tournament size)
base.n int > 0	(the number of best-individuals to select from)
base.n-fraction 0.0 <= double < 1.0 (default is 1)	(the number of best-individuals to select from, as a fraction of the total population)

Default Base
select.best

Version:

1.0

Author:

Sean Luke

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
int	bestn
double	bestnFrac
static int	NOT_SET
static String	P_BEST Default base
static String	P_N
static String	P_N_FRACTION
static String	P_PICKWORST
static String	P_SIZE
boolean	pickWorst Do we pick the worst instead of the best?
double	probabilityOfPickingSizePlusOne Probablity of picking the size plus one.
int	size Base size of the tournament; this may change.
int[]	sortedPop Sorted, normalized, totalized fitnesses for the population

Fields inherited from class ec.SelectionMethod

INDS_PRODUCED, KEY_PARENTS

Fields inherited from class ec.BreedingSource

NO_PROBABILITY, P_PROB, probability

Constructor Summary

Constructors

Constructor and Description
BestSelection()

Method Summary

Modifier and Type	Method and Description
Parameter	defaultBase() Returns the default base for this prototype.
void	finishProducing(EvolutionState s, int subpopulation, int thread) A default version of finishProducing, which does nothing.
(package private) int	getTournamentSizeToUse(MersenneTwisterFast random) Returns a tournament size to use, at random, based on base size and probability of picking the size plus one.
void	prepareToProduce(EvolutionState s, int subpopulation, int thread) A default version of prepareToProduce which does nothing.
int	produce(int subpopulation, EvolutionState state, int thread) An alternative form of "produce" special to Selection Methods; selects an individual from the given subpopulation and returns its position in that subpopulation.
void	setup(EvolutionState state, Parameter base) Sets up the BreedingPipeline.

Methods inherited from class ec.SelectionMethod

produce, produces, produceWithoutCloning, typicalIndsProduced

Methods inherited from class ec.BreedingSource

clone, fillStubs, getProbability, pickRandom, preparePipeline, setProbability, setupProbabilities

Methods inherited from class java.lang.Object

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

Field Detail

P_BEST

public static final String P_BEST

Default base

See Also:

Constant Field Values

P_N

public static final String P_N

See Also:

Constant Field Values

P_N_FRACTION

public static final String P_N_FRACTION

See Also:

Constant Field Values

P_PICKWORST

public static final String P_PICKWORST

See Also:

Constant Field Values

P_SIZE

public static final String P_SIZE

See Also:

Constant Field Values

size

public int size

Base size of the tournament; this may change.

probabilityOfPickingSizePlusOne

public double probabilityOfPickingSizePlusOne

Probablity of picking the size plus one.

pickWorst

public boolean pickWorst

Do we pick the worst instead of the best?

sortedPop

public int[] sortedPop

Sorted, normalized, totalized fitnesses for the population

NOT_SET

public static final int NOT_SET

See Also:

Constant Field Values

bestn

public int bestn

bestnFrac

public double bestnFrac

Constructor Detail

BestSelection

public BestSelection()

Method Detail

defaultBase

public Parameter defaultBase()

Description copied from interface: Prototype

Returns the default base for this prototype. This should generally be implemented by building off of the static base() method on the DefaultsForm object for the prototype's package. This should be callable during setup(...).

setup

public void setup(EvolutionState state,
                  Parameter base)

Description copied from class: BreedingSource

Sets up the BreedingPipeline. You can use state.output.error here because the top-level caller promises to call exitIfErrors() after calling setup. Note that probability might get modified again by an external source if it doesn't normalize right.

The most common modification is to normalize it with some other set of probabilities, then set all of them up in increasing summation; this allows the use of the fast static BreedingSource-picking utility method, BreedingSource.pickRandom(...). In order to use this method, for example, if four breeding source probabilities are {0.3, 0.2, 0.1, 0.4}, then they should get normalized and summed by the outside owners as: {0.3, 0.5, 0.6, 1.0}.

Specified by:

setup in interface Prototype

Specified by:

setup in interface Setup

Overrides:

setup in class BreedingSource

See Also:

Prototype.setup(EvolutionState,Parameter)

prepareToProduce

public void prepareToProduce(EvolutionState s,
                             int subpopulation,
                             int thread)

Description copied from class: SelectionMethod

A default version of prepareToProduce which does nothing.

Overrides:

prepareToProduce in class SelectionMethod

getTournamentSizeToUse

int getTournamentSizeToUse(MersenneTwisterFast random)

Returns a tournament size to use, at random, based on base size and probability of picking the size plus one.

produce

public int produce(int subpopulation,
                   EvolutionState state,
                   int thread)

Description copied from class: SelectionMethod

An alternative form of "produce" special to Selection Methods; selects an individual from the given subpopulation and returns its position in that subpopulation.

Specified by:

produce in class SelectionMethod

finishProducing

public void finishProducing(EvolutionState s,
                            int subpopulation,
                            int thread)

Description copied from class: SelectionMethod

A default version of finishProducing, which does nothing.

Overrides:

finishProducing in class SelectionMethod