org.jgap
Class Population

java.lang.Object
  org.jgap.Population

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, IPersistentRepresentation, ICloneable

public class Population
extends java.lang.Object
implements java.io.Serializable, ICloneable, IPersistentRepresentation

Makes up the population of a generation during evolution. Represented by a list of chromosomes held in the Genotype.

Since:

2.0

See Also:

Serialized Form

Field Summary

static java.lang.String	CHROM_DELIMITER
static java.lang.String	CHROM_DELIMITER_CLOSING Represents the closing delimiter that is used to separate chromosomes in the persistent representation.
static java.lang.String	CHROM_DELIMITER_HEADING Represents the heading delimiter that is used to separate chromosomes in the persistent representation.

Constructor Summary

Population()

Population(Configuration a_config)

Population(Configuration a_config, IChromosome a_chromosome)

Population(Configuration a_config, IChromosome[] a_chromosomes)

Population(Configuration a_config, int a_size)

Method Summary

void	addChromosome(IChromosome a_toAdd) Adds a Chromosome to this Population.
void	addChromosomes(Population a_population) Adds all the Chromosomes in the given Population.
void	clear() Clears the list of chromosomes.
java.lang.Object	clone()
int	compareTo(java.lang.Object a_pop) This method is not producing symmetric results as -1 is more often returned than 1 (see description of return value).
boolean	contains(IChromosome a_chromosome) Determines whether the given chromosome is contained within the population.
protected IChromosome	createChromosome(java.lang.String a_chromClassName, java.lang.String a_persistentRepresentation) Creates a new Chromosome instance.
IChromosome	determineFittestChromosome() Determines the fittest Chromosome in the Population (the one with the highest fitness value) and memorizes it.
IChromosome	determineFittestChromosome(int a_startIndex, int a_endIndex) Determines the fittest Chromosome in the population (the one with the highest fitness value) within the given indices and memorizes it.
java.util.List	determineFittestChromosomes(int a_numberOfChromosomes) Sorts the Chromosome list and returns the fittest n Chromosomes in the population.
boolean	equals(java.lang.Object a_pop) The equals-method.
IChromosome	getChromosome(int a_index)
java.util.List<IChromosome>	getChromosomes()
Configuration	getConfiguration()
java.util.List	getGenome(boolean a_resolveCompositeGenes) Returns the genotype of the population, i.e. the list of genes in the Population.
java.lang.String	getPersistentRepresentation() Returns a persistent representation of this chromosome, see interface Gene for description.
int	hashCode() Hashcode function for the genotype, tries to create a unique hashcode for the chromosomes within the population.
boolean	isChanged()
boolean	isSorted()
java.util.Iterator	iterator()
void	keepPopSizeConstant() Cares that the population size does not exceed the maximum size given in the configuration.
protected void	setChanged(boolean a_changed) Mark that for the population the fittest chromosome may have changed.
void	setChromosome(int a_index, IChromosome a_chromosome) Sets in the given Chromosome on the given index in the list of chromosomes.
void	setChromosomes(java.util.List a_chromosomes) Replaces all chromosomes in the population with the give list of chromosomes.
protected void	setSorted(boolean a_sorted) Mark the population as sorted.
void	setValueFromPersistentRepresentation(java.lang.String a_representation) Counterpart of getPersistentRepresentation.
int	size()
protected void	sort(java.util.Comparator a_comparator) Sorts the chromosomes within the population utilzing the given comparator.
void	sortByFitness() Sorts the chromosomes within the population according to their fitness value using ChromosomFitnessComparator.
protected static java.util.List	split(java.lang.String a_string) Splits the input a_string into individual chromosome representations.
IChromosome[]	toChromosomes()

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

CHROM_DELIMITER

public static final java.lang.String CHROM_DELIMITER

See Also:

Constant Field Values

CHROM_DELIMITER_HEADING

public static final java.lang.String CHROM_DELIMITER_HEADING

Represents the heading delimiter that is used to separate chromosomes in the persistent representation.

See Also:

Constant Field Values

CHROM_DELIMITER_CLOSING

public static final java.lang.String CHROM_DELIMITER_CLOSING

Represents the closing delimiter that is used to separate chromosomes in the persistent representation.

See Also:

Constant Field Values

Constructor Detail

Population

public Population(Configuration a_config)
           throws InvalidConfigurationException

Throws:

InvalidConfigurationException

Population

public Population(Configuration a_config,
                  IChromosome[] a_chromosomes)
           throws InvalidConfigurationException

Throws:

InvalidConfigurationException

Population

public Population(Configuration a_config,
                  IChromosome a_chromosome)
           throws InvalidConfigurationException

Throws:

InvalidConfigurationException

Population

public Population(Configuration a_config,
                  int a_size)
           throws InvalidConfigurationException

Throws:

InvalidConfigurationException

Population

public Population()
           throws InvalidConfigurationException

Throws:

InvalidConfigurationException

Method Detail

getConfiguration

public Configuration getConfiguration()

addChromosome

public void addChromosome(IChromosome a_toAdd)

Adds a Chromosome to this Population. Does nothing when given null.

Parameters:

a_toAdd - the Chromosome to add

Since:

2.0

addChromosomes

public void addChromosomes(Population a_population)

Adds all the Chromosomes in the given Population. Does nothing on null or an empty Population.

Parameters:

a_population - the Population to add

Since:

2.0

setChromosomes

public void setChromosomes(java.util.List a_chromosomes)

Replaces all chromosomes in the population with the give list of chromosomes.

Parameters:

a_chromosomes - the chromosomes to make the population up from

setChromosome

public void setChromosome(int a_index,
                          IChromosome a_chromosome)

Sets in the given Chromosome on the given index in the list of chromosomes. If the given index is exceeding the list by one, the chromosome is appended.

Parameters:

a_index - the index to set the Chromosome in

a_chromosome - the Chromosome to be set

Since:

2.0

getChromosomes

public java.util.List<IChromosome> getChromosomes()

Returns:

the list of Chromosome's in the Population. Don't modify the retrieved list by using clear(), remove(int) etc. If you do so, you need to call setChanged(true)

Since:

2.0

getChromosome

public IChromosome getChromosome(int a_index)

Parameters:

a_index - the index of the Chromosome to be returned

Returns:

Chromosome at given index in the Population

Since:

2.0

size

public int size()

Returns:

number of Chromosome's in the Population

Since:

2.0

iterator

public java.util.Iterator iterator()

Returns:

Iterator for the Chromosome list in the Population. Please be aware that using remove() forces you to call setChanged(true)

Since:

2.0

toChromosomes

public IChromosome[] toChromosomes()

Returns:

the Population converted into a list of Chromosome's

Since:

2.0

determineFittestChromosome

public IChromosome determineFittestChromosome()

Determines the fittest Chromosome in the Population (the one with the highest fitness value) and memorizes it. This is an optimized version compared to calling determineFittesChromosomes(1).

Returns:

the fittest Chromosome of the Population

Since:

2.0

determineFittestChromosome

public IChromosome determineFittestChromosome(int a_startIndex,
                                              int a_endIndex)

Determines the fittest Chromosome in the population (the one with the highest fitness value) within the given indices and memorizes it. This is an optimized version compared to calling determineFittesChromosomes(1).

Parameters:

a_startIndex - index to begin the evaluation with

a_endIndex - index to end the evaluation with

Returns:

the fittest Chromosome of the population within the given indices

Since:

3.0

setChanged

protected void setChanged(boolean a_changed)

Mark that for the population the fittest chromosome may have changed.

Parameters:

a_changed - true: population's fittest chromosome may have changed, false: fittest chromosome evaluated earlier is still valid

Since:

2.2

isChanged

public boolean isChanged()

Returns:

true: population's chromosomes (maybe) were changed, false: not changed for sure

Since:

2.6

setSorted

protected void setSorted(boolean a_sorted)

Mark the population as sorted.

Parameters:

a_sorted - true: mark population as sorted

Since:

2.6

contains

public boolean contains(IChromosome a_chromosome)

Determines whether the given chromosome is contained within the population.

Parameters:

a_chromosome - the chromosome to check

Returns:

true: chromosome contained within population

Since:

2.1

keepPopSizeConstant

public void keepPopSizeConstant()
                         throws InvalidConfigurationException

Cares that the population size does not exceed the maximum size given in the configuration.

Throws:

InvalidConfigurationException

Since:

3.2

determineFittestChromosomes

public java.util.List determineFittestChromosomes(int a_numberOfChromosomes)

Sorts the Chromosome list and returns the fittest n Chromosomes in the population.

Parameters:

a_numberOfChromosomes - number of top performer chromosomes to be returned

Returns:

list of the fittest n Chromosomes of the population, or the fittest x Chromosomes with x = number of chromosomes in case n > x.

Since:

2.4

sortByFitness

public void sortByFitness()

Sorts the chromosomes within the population according to their fitness value using ChromosomFitnessComparator. The fittest chromosome is then at index 0.

Since:

2.6

sort

protected void sort(java.util.Comparator a_comparator)

Sorts the chromosomes within the population utilzing the given comparator.

Parameters:

a_comparator - the comparator to utilize for sorting

Since:

2.6

getGenome

public java.util.List getGenome(boolean a_resolveCompositeGenes)

Returns the genotype of the population, i.e. the list of genes in the Population.

Parameters:

a_resolveCompositeGenes - true: split encountered CompositeGenes into their single (atomic) genes

Returns:

genotype of the population

Since:

2.3

isSorted

public boolean isSorted()

equals

public boolean equals(java.lang.Object a_pop)

The equals-method.

Overrides:

equals in class java.lang.Object

Parameters:

a_pop - the population instance to compare with

Returns:

true: given object equal to comparing one

Since:

2.6

compareTo

public int compareTo(java.lang.Object a_pop)

This method is not producing symmetric results as -1 is more often returned than 1 (see description of return value).

Parameters:

a_pop - the other population to compare

Returns:

1: a_pop is null or having fewer chromosomes or equal number of chromosomes but at least one not contained. 0: both populations containing exactly the same chromosomes. -1: this population contains fewer chromosomes than a_pop

Since:

2.6

clone

public java.lang.Object clone()

Specified by:

clone in interface ICloneable

Overrides:

clone in class java.lang.Object

Returns:

deeply cloned population instance

Since:

3.2

clear

public void clear()

Clears the list of chromosomes. Normally, this should not be necessary. But especially in distributed computing, a fresh population has to be provided sometimes.

Since:

3.2

getPersistentRepresentation

public java.lang.String getPersistentRepresentation()

Returns a persistent representation of this chromosome, see interface Gene for description. Similar to CompositeGene's routine. But does not include all information of the chromosome (yet).

Specified by:

getPersistentRepresentation in interface IPersistentRepresentation

Returns:

string representation of this Chromosome's relevant parts of its current state

Throws:

java.lang.UnsupportedOperationException

Since:

3.2

setValueFromPersistentRepresentation

public void setValueFromPersistentRepresentation(java.lang.String a_representation)
                                          throws UnsupportedRepresentationException

Counterpart of getPersistentRepresentation.

Specified by:

setValueFromPersistentRepresentation in interface IPersistentRepresentation

Parameters:

a_representation - the string representation retrieved from a prior call to the getPersistentRepresentation() method

Throws:

UnsupportedRepresentationException

Since:

3.2

createChromosome

protected IChromosome createChromosome(java.lang.String a_chromClassName,
                                       java.lang.String a_persistentRepresentation)
                                throws java.lang.Exception

Creates a new Chromosome instance.

Taken and adapted from CompositeGene.

Parameters:

a_chromClassName - name of the Chromosome class

a_persistentRepresentation - persistent representation of the Chromosome to create (could be obtained via getPersistentRepresentation)

Returns:

newly created Chromosome

Throws:

java.lang.Exception

Since:

3.2

split

protected static final java.util.List split(java.lang.String a_string)
                                     throws UnsupportedRepresentationException

Splits the input a_string into individual chromosome representations.

Taken and adapted from CompositeGene.

Parameters:

a_string - the string to split

Returns:

the elements of the returned array are the persistent representation strings of the population's components

Throws:

UnsupportedRepresentationException

Since:

3.2

hashCode

public int hashCode()

Hashcode function for the genotype, tries to create a unique hashcode for the chromosomes within the population. The logic for the hashcode is Step Result ---- ------ 1 31*0 + hashcode_0 = y(1) 2 31*y(1) + hashcode_1 = y(2) 3 31*y(2) + hashcode_2 = y(3) n 31*y(n-1) + hashcode_n-1 = y(n)

Overrides:

hashCode in class java.lang.Object

Returns:

the computed hashcode

Since:

3.5