org.artoflife.gp.population
Class GenerationalPopulation

java.lang.Object
  |
  +--org.artoflife.gp.Population
        |
        +--org.artoflife.gp.population.GenerationalPopulation

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

MinFitnessGenerationalPopulation, SelectorGenerationalPopulation

public abstract class GenerationalPopulation

extends Population

A Population that breeds new Individuals into the main population to replace dead ones.

A breeding cycle looks like:

1. Cull some Individuals from the main population,
2. Breed new offspring by selection among the survivors until the population is up to the right size.

The culling strategy is implemented in concrete subclasses, but this base class implements a breeding strategy based on selection using a Selector defined by makeSelector() which can be overridden.

Author:

Steve Meyfroidt

See Also:

Serialized Form

Field Summary

protected static java.util.Comparator	FITNESS_COMPARATOR Shared instance.
protected java.lang.Class	individualClass
protected int	populationSize
protected java.lang.Class	selectorClass

Fields inherited from class org.artoflife.gp.Population

individuals

Constructor Summary

GenerationalPopulation(int populationSize, java.lang.Class individualClass, java.util.SortedMap reproducers)

Method Summary

protected void	breed() Override to implement breeding policy, returning the population size to the getIdealPopulationSize().
int	getIdealPopulationSize() Can be overriden.
protected Selector	makeSelector() Create a new Selector.
Individual	newIndividual() Create a new Individual.
void	setIdealPopulationSize(int idealSize)
void	setSelectorClass(java.lang.Class selectorClass)

Methods inherited from class org.artoflife.gp.Population

addIndividual, addNewIndividuals, addPopulationListener, breedNewIndividual, cullOneWeakest, cullWeakest, firePopulationEvent, getIndividuals, getReproducers, newGeneration, removeIndividual, removePopulationListener

Methods inherited from class java.lang.Object

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

Field Detail

FITNESS_COMPARATOR

protected static final java.util.Comparator FITNESS_COMPARATOR

Shared instance.

selectorClass

protected java.lang.Class selectorClass

populationSize

protected int populationSize

individualClass

protected java.lang.Class individualClass

Constructor Detail

GenerationalPopulation

public GenerationalPopulation(int populationSize,
                              java.lang.Class individualClass,
                              java.util.SortedMap reproducers)

Parameters:

populationSize - how many Individuals in this fixed size population? Must be > 2

individualClass - Class of individuals to create as initial population. Must be non-null

reproducers - to use when breeding new generation. See Configuration.getInstancesProbabilities(String)

Method Detail

setSelectorClass

public void setSelectorClass(java.lang.Class selectorClass)

breed

protected void breed()

Description copied from class: Population

Override to implement breeding policy, returning the population size to the Population.getIdealPopulationSize(). For example you could fill a nursery by mating strongest Individuals in Population then move strongest from nursery into main population. This is called after Population.cullWeakest() on each new generation.

Specified by:

breed in class Population

See Also:

Population.breed()

makeSelector

protected Selector makeSelector()

Create a new Selector.

See Also:

setSelectorClass(Class)

getIdealPopulationSize

public int getIdealPopulationSize()

Can be overriden. Here returns a constant passed at construction.

Specified by:

getIdealPopulationSize in class Population

Returns:

the number of Individuals that the population aims to maintain in Population.newGeneration().

setIdealPopulationSize

public void setIdealPopulationSize(int idealSize)

Specified by:

setIdealPopulationSize in class Population

Parameters:

idealSize - the number of Individuals that the population aims to maintain in Population.newGeneration().

newIndividual

public Individual newIndividual()

Create a new Individual. Used to fill the Population upon construction. Default implementation here creates a new instance of the class passed on construction. Override for other behaviour.

Specified by:

newIndividual in class Population

Returns:

a newly bred Individual