Package ec.parsimony

Class BucketTournamentSelection

java.lang.Object

ec.BreedingSource

ec.SelectionMethod

ec.parsimony.BucketTournamentSelection

All Implemented Interfaces:

Prototype, Setup, SteadyStateBSourceForm, RandomChoiceChooserD, Serializable, Cloneable

public class BucketTournamentSelection
extends SelectionMethod
implements SteadyStateBSourceForm

Does a tournament selection, limited to the subpopulation it's working in at the time.

Bucket Lexicographic Tournament selection works like as follows. There is a number of buckets (num-buckets) specified beforehand, and each is assigned a rank from 1 to num-buckets. The population, of size pop-size, is sorted by fitness. The bottom pop-size/num-buckets individuals are placed in the worst ranked bucket, plus any individuals remaining in the population with the same fitness as the best individual in the bucket. Then the second worst pop-size/num-buckets individuals are placed in the second worst ranked bucket, plus any individuals in the population equal in fitness to the best individual in that bucket. This continues until there are no individuals in the population. Note that the topmost bucket with individuals can hold fewer than pop-size/num-buckets individuals, if pop-size is not a multiple of num-buckets. Depending on the number of equal-fitness individuals in the population, there can be some top buckets that are never filled. The fitness of each individual in a bucket is set to the rank of the bucket holding it. Direct bucketing has the effect of trading off fitness differences for size. Thus the larger the bucket, the stronger the emphasis on size as a secondary objective. After ranking the individuals, size individuals are chosen at random from the population. Of those individuals, the one with the highest rank is selected. If the two individuals are in the same rank, meaning that they have similar fitness, the one with the smallest size is selected.

Bucket Lexicographic Tournament selection is so simple that it doesn't need to maintain a cache of any form, so many of the SelectionMethod methods just don't do anything at all.

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

Parameters

base.size int >= 1 (default 7)	(the tournament size)
base.pick-worst bool = true or false (default)	(should we pick the worst individual in the tournament instead of the best?)
base.num-buckets int >= 1 (default 10)	(the number of buckets)

Default Base
select.bucket-tournament

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final int	N_BUCKETS_DEFAULT	Default number of buckets
static final String	P_BUCKETS	The number of buckets
static final String	P_PICKWORST	If the worst individual should be picked in the tournament
static final String	P_SIZE	Tournament size parameter
static final String	P_TOURNAMENT	Default base
boolean	pickWorst	Do we pick the worst instead of the best?
int	size	Size of the tournament

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	Description
BucketTournamentSelection()

Method Summary

Modifier and Type	Method	Description
Parameter	defaultBase()	Returns the default base for this prototype.
void	individualReplaced(SteadyStateEvolutionState state, int subpopulation, int thread, int individual)	Called whenever an individual has been replaced by another in the population.
void	prepareToProduce(EvolutionState state, int subpopulation, int thread)	Prepare to produce: create the buckets!!!!
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.
void	sourcesAreProperForm(SteadyStateEvolutionState state)	Issue an error (not a fatal -- we guarantee that callers of this method will also call exitIfErrors) if any of your sources, or their sources, etc., are not of SteadyStateBSourceForm.

Methods inherited from class ec.SelectionMethod

finishProducing, 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 Details

P_TOURNAMENT

public static final String P_TOURNAMENT

Default base

See Also:

• Constant Field Values

P_PICKWORST

public static final String P_PICKWORST

If the worst individual should be picked in the tournament

See Also:

• Constant Field Values

P_SIZE

public static final String P_SIZE

Tournament size parameter

See Also:

• Constant Field Values

P_BUCKETS

public static final String P_BUCKETS

The number of buckets

See Also:

• Constant Field Values

N_BUCKETS_DEFAULT

public static final int N_BUCKETS_DEFAULT

Default number of buckets

See Also:

• Constant Field Values

size

public int size

Size of the tournament

pickWorst

public boolean pickWorst

Do we pick the worst instead of the best?

Constructor Details

BucketTournamentSelection

public BucketTournamentSelection()

Method Details

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(...).

Specified by:

defaultBase in interface Prototype

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 state,
 int subpopulation,
 int thread)

Prepare to produce: create the buckets!!!!

Overrides:

prepareToProduce in class SelectionMethod

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

individualReplaced

public void individualReplaced(SteadyStateEvolutionState state,
 int subpopulation,
 int thread,
 int individual)

Description copied from interface: SteadyStateBSourceForm

Called whenever an individual has been replaced by another in the population.

Specified by:

individualReplaced in interface SteadyStateBSourceForm

sourcesAreProperForm

public void sourcesAreProperForm(SteadyStateEvolutionState state)

Description copied from interface: SteadyStateBSourceForm

Issue an error (not a fatal -- we guarantee that callers of this method will also call exitIfErrors) if any of your sources, or their sources, etc., are not of SteadyStateBSourceForm.

Specified by:

sourcesAreProperForm in interface SteadyStateBSourceForm