ec.select
Class GreedyOverselection

java.lang.Object
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  +--ec.BreedingSource
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        +--ec.SelectionMethod
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              +--ec.select.GreedyOverselection

public class GreedyOverselection
extends SelectionMethod

GreedyOverselection is a SelectionMethod which implements Koza-style fitness-proportionate greedy overselection. Not appropriate for multiobjective fitnesses.

This selection method first divides individuals in a population into two groups: the "good" ("top") group, and the "bad" ("bottom") group. The best top percent of individuals in the population go into the good group. The rest go into the "bad" group. With a certain probability (determined by the gets setting), an individual will be picked out of the "good" group. Once we have determined which group the individual will be selected from, the individual is picked using fitness proportionate selection in that group, that is, the likelihood he is picked is proportionate to his fitness relative to the fitnesses of others in his group.

All this is expensive to set up and bring down, so it's not appropriate for steady-state evolution. If you're not familiar with the relative advantages of selection methods and just want a good one, use TournamentSelection instead.

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

Parameters
base.top
0.0 <= float <= 1.0
(the percentage of the population going into the "good" (top) group)
base.gets
0.0 <= float <= 1.0
(the likelihood that an individual will be picked from the "good" group)

Default Base
select.greedy

See Also:
Serialized Form

Field Summary
static int CHECKBOUNDARY
          CheckBoundary is 8
 float gets_n_percent
           
static java.lang.String P_GETS
           
static java.lang.String P_GREEDY
           
static java.lang.String P_TOP
           
 float[] sortedFitOver
           
 float[] sortedFitUnder
           
 int[] sortedPop
          Sorted population -- since I *have* to use an int-sized individual (short gives me only 16K), I might as well just have pointers to the population itself.
 float top_n_percent
           
 
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
GreedyOverselection()
           
 
Method Summary
 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.
 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
preparePipeline, produce, produces, typicalIndsProduced
 
Methods inherited from class ec.BreedingSource
getProbability, pickRandom, protoClone, protoCloneSimple, setProbability, setupProbabilities
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

CHECKBOUNDARY

public static final int CHECKBOUNDARY
CheckBoundary is 8

sortedFitOver

public float[] sortedFitOver

sortedFitUnder

public float[] sortedFitUnder

sortedPop

public int[] sortedPop
Sorted population -- since I *have* to use an int-sized individual (short gives me only 16K), I might as well just have pointers to the population itself. :-(

P_GREEDY

public static final java.lang.String P_GREEDY

P_TOP

public static final java.lang.String P_TOP

P_GETS

public static final java.lang.String P_GETS

top_n_percent

public float top_n_percent

gets_n_percent

public float gets_n_percent
Constructor Detail

GreedyOverselection

public GreedyOverselection()
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}.

Overrides:
setup in class BreedingSource
Tags copied from 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

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.
Overrides:
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