Package ec.parsimony

Class RatioBucketTournamentSelection

java.lang.Object

ec.BreedingSource

ec.SelectionMethod

ec.parsimony.RatioBucketTournamentSelection

All Implemented Interfaces:

Prototype, Setup, SteadyStateBSourceForm, RandomChoiceChooserD, Serializable, Cloneable

public class RatioBucketTournamentSelection
extends SelectionMethod
implements SteadyStateBSourceForm

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

Ratio Bucket Lexicographic Tournament selection works like as follows. The sizes of buckets are proportioned so that low-fitness individuals are placed into much larger buckets than high-fitness individuals. A bucket ratio 1/ratio is specified beforehand. The bottom 1/ratio individuals of the population are placed into the bottom bucket. If any individuals remain in the population with the same fitness as the best individual in the bottom bucket, they too are placed in that bucket. Of the remaining population, the next 1/ratio individuals are placed into the next bucket, plus any individuals remaining in the population with the same fitness as the best individual now in that bucket, and so on. This continues until every member of the population has been placed in a bucket. Once again, the fitness of every individual in a bucket is set to the rank of the bucket relative to other buckets. Ratio bucketing thus allows parsimony to have more of an effect on average when two similar low-fitness individuals are considered than when two high-fitness individuals are considered. 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.ratio double >= 2 (default)	(the ratio of worst out of remaining individuals that go in the next bucket)

Default Base
select.ratio-bucket-tournament

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final String	P_PICKWORST	if the worst individual should be picked in the tournament
static final String	P_RATIO	The value of RATIO: each step, the worse 1/RATIO individuals are assigned the same fitness
static final String	P_RATIO_BUCKET_TOURNAMENT	default base
static final String	P_SIZE	size parameter
boolean	pickWorst	Do we pick the worst instead of the best?
double	ratio	The value of RATIO
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
RatioBucketTournamentSelection()

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_RATIO_BUCKET_TOURNAMENT

public static final String P_RATIO_BUCKET_TOURNAMENT

default base

See Also:

• Constant Field Values

P_SIZE

public static final String P_SIZE

size parameter

See Also:

• Constant Field Values

size

public int size

Size of the tournament

P_PICKWORST

public static final String P_PICKWORST

if the worst individual should be picked in the tournament

See Also:

• Constant Field Values

pickWorst

public boolean pickWorst

Do we pick the worst instead of the best?

P_RATIO

public static final String P_RATIO

The value of RATIO: each step, the worse 1/RATIO individuals are assigned the same fitness

See Also:

• Constant Field Values

ratio

public double ratio

The value of RATIO

Constructor Details

RatioBucketTournamentSelection

public RatioBucketTournamentSelection()

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