ec.parsimony
Class RatioBucketTournamentSelection

java.lang.Object
  extended by ec.BreedingSource
      extended by ec.SelectionMethod
          extended by ec.parsimony.RatioBucketTournamentSelection
All Implemented Interfaces:
Prototype, Setup, SteadyStateBSourceForm, RandomChoiceChooser, java.io.Serializable, java.lang.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
float >= 2 (default)
(the ratio of worst out of remaining individuals that go in the next bucket)

Default Base
select.ratio-bucket-tournament

Version:
1.0
Author:
Liviu Panait
See Also:
Serialized Form

Field Summary
static int DEFAULT_SIZE
          Default size
static java.lang.String P_PICKWORST
          if the worst individual should be picked in the tournament
static java.lang.String P_RATIO
          The value of RATIO: each step, the worse 1/RATIO individuals are assigned the same fitness
static java.lang.String P_SIZE
          size parameter
static java.lang.String P_TOURNAMENT
          default base
 boolean pickWorst
          Do we pick the worst instead of the best?
 float ratio
          The value of RATIO
 int size
          Size of the tournament
 
Fields inherited from class ec.SelectionMethod
INDS_PRODUCED
 
Fields inherited from class ec.BreedingSource
CHECKBOUNDARY, DEFAULT_PRODUCED, NO_PROBABILITY, P_PROB, probability, UNUSED
 
Constructor Summary
RatioBucketTournamentSelection()
           
 
Method Summary
 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, preparePipeline, produce, produces, typicalIndsProduced
 
Methods inherited from class ec.BreedingSource
clone, getProbability, pickRandom, setProbability, setupProbabilities
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

P_TOURNAMENT

public static final java.lang.String P_TOURNAMENT
default base

See Also:
Constant Field Values

P_SIZE

public static final java.lang.String P_SIZE
size parameter

See Also:
Constant Field Values

DEFAULT_SIZE

public static final int DEFAULT_SIZE
Default size

See Also:
Constant Field Values

size

public int size
Size of the tournament


P_PICKWORST

public static final java.lang.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 java.lang.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 float ratio
The value of RATIO

Constructor Detail

RatioBucketTournamentSelection

public RatioBucketTournamentSelection()
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(...).

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