C# Class AForge.Genetic.Population

Population of chromosomes.

The class represents population - collection of individuals (chromosomes) and provides functionality for common population's life cycle - population growing with help of genetic operators and selection of chromosomes to new generation with help of selection algorithm. The class may work with any type of chromosomes implementing IChromosome interface, use any type of fitness functions implementing IFitnessFunction interface and use any type of selection algorithms implementing ISelectionMethod interface.

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Public Methods

Method	Description
AddChromosome ( IChromosome chromosome ) : void	Add chromosome to the population. The method adds specified chromosome to the current population. Manual adding of chromosome maybe useful, when it is required to add some initialized chromosomes instead of random. Adding chromosome manually should be done very carefully, since it may break the population. The manually added chromosome must have the same type and initialization parameters as the ancestor passed to constructor.
Crossover ( ) : void	Do crossover in the population. The method walks through the population and performs crossover operator taking each two chromosomes in the order of their presence in the population. The total amount of paired chromosomes is determined by crossover rate.
Migrate ( Population anotherPopulation, int numberOfMigrants, ISelectionMethod migrantsSelector ) : void	Perform migration between two populations. The method performs migration between two populations - current and the specified one. During migration specified number of chromosomes is choosen from each population using specified selection algorithms and put into another population replacing worst members there.
Mutate ( ) : void	Do mutation in the population. The method walks through the population and performs mutation operator taking each chromosome one by one. The total amount of mutated chromosomes is determined by mutation rate.
Population ( int size, IChromosome ancestor, IFitnessFunction fitnessFunction, ISelectionMethod selectionMethod ) : System	Initializes a new instance of the Population class. Creates new population of specified size. The specified ancestor becomes first member of the population and is used to create other members with same parameters, which were used for ancestor's creation.
Regenerate ( ) : void	Regenerate population. The method regenerates population filling it with random chromosomes.
Resize ( int newPopulationSize ) : void	Resize population to the new specified size. The method does resizing of population. In the case if population should grow, it just adds missing number of random members. In the case if population should get smaller, the population's selection method is used to reduce the population.
Resize ( int newPopulationSize, ISelectionMethod membersSelector ) : void	Resize population to the new specified size. The method does resizing of population. In the case if population should grow, it just adds missing number of random members. In the case if population should get smaller, the specified selection method is used to reduce the population.
RunEpoch ( ) : void	Run one epoch of the population. The method runs one epoch of the population, doing crossover, mutation and selection by calling Crossover, Mutate and Selection.
Selection ( ) : void	Do selection. The method applies selection operator to the current population. Using specified selection algorithm it selects members to the new generation from current generates and adds certain amount of random members, if is required (see RandomSelectionPortion).
Shuffle ( ) : void	Shuffle randomly current population. Population shuffling may be useful in cases when selection operator results in not random order of chromosomes (for example, after elite selection population may be ordered in ascending/descending order).
this ( int index ) : IChromosome	Get chromosome with specified index. Allows to access individuals of the population.

Private Methods

Method	Description
FindBestChromosome ( ) : void

Method Details

AddChromosome() public method

Add chromosome to the population.

The method adds specified chromosome to the current population. Manual adding of chromosome maybe useful, when it is required to add some initialized chromosomes instead of random.

Adding chromosome manually should be done very carefully, since it may break the population. The manually added chromosome must have the same type and initialization parameters as the ancestor passed to constructor.

public AddChromosome ( IChromosome chromosome ) : void
chromosome	IChromosome	Chromosome to add to the population.
return	void

Crossover() public method

Do crossover in the population.

The method walks through the population and performs crossover operator taking each two chromosomes in the order of their presence in the population. The total amount of paired chromosomes is determined by crossover rate.

public Crossover ( ) : void
return	void

Migrate() public method

Perform migration between two populations.

The method performs migration between two populations - current and the specified one. During migration specified number of chromosomes is choosen from each population using specified selection algorithms and put into another population replacing worst members there.

public Migrate ( Population anotherPopulation, int numberOfMigrants, ISelectionMethod migrantsSelector ) : void
anotherPopulation	Population	Population to do migration with.
numberOfMigrants	int	Number of chromosomes from each population to migrate.
migrantsSelector	ISelectionMethod	Selection algorithm used to select chromosomes to migrate.
return	void

Mutate() public method

Do mutation in the population.

The method walks through the population and performs mutation operator taking each chromosome one by one. The total amount of mutated chromosomes is determined by mutation rate.

public Mutate ( ) : void
return	void

Population() public method

Initializes a new instance of the Population class.

Creates new population of specified size. The specified ancestor becomes first member of the population and is used to create other members with same parameters, which were used for ancestor's creation.

Too small population's size was specified. The /// exception is thrown in the case if is smaller than 2.

public Population ( int size, IChromosome ancestor, IFitnessFunction fitnessFunction, ISelectionMethod selectionMethod ) : System
size	int	Initial size of population.
ancestor	IChromosome	Ancestor chromosome to use for population creatioin.
fitnessFunction	IFitnessFunction	Fitness function to use for calculating /// chromosome's fitness values.
selectionMethod	ISelectionMethod	Selection algorithm to use for selection /// chromosome's to new generation.
return	System

Regenerate() public method

Regenerate population.

The method regenerates population filling it with random chromosomes.

public Regenerate ( ) : void
return	void

Resize() public method

Resize population to the new specified size.

The method does resizing of population. In the case if population should grow, it just adds missing number of random members. In the case if population should get smaller, the population's selection method is used to reduce the population.

Too small population's size was specified. The /// exception is thrown in the case if is smaller than 2.

public Resize ( int newPopulationSize ) : void
newPopulationSize	int	New size of population.
return	void

Resize() public method

Resize population to the new specified size.

The method does resizing of population. In the case if population should grow, it just adds missing number of random members. In the case if population should get smaller, the specified selection method is used to reduce the population.

Too small population's size was specified. The /// exception is thrown in the case if is smaller than 2.

public Resize ( int newPopulationSize, ISelectionMethod membersSelector ) : void
newPopulationSize	int	New size of population.
membersSelector	ISelectionMethod	Selection algorithm to use in the case /// if population should get smaller.
return	void

RunEpoch() public method

Run one epoch of the population.

The method runs one epoch of the population, doing crossover, mutation and selection by calling Crossover, Mutate and Selection.

public RunEpoch ( ) : void
return	void

Selection() public method

Do selection.

The method applies selection operator to the current population. Using specified selection algorithm it selects members to the new generation from current generates and adds certain amount of random members, if is required (see RandomSelectionPortion).

public Selection ( ) : void
return	void

Shuffle() public method

Shuffle randomly current population.

Population shuffling may be useful in cases when selection operator results in not random order of chromosomes (for example, after elite selection population may be ordered in ascending/descending order).

public Shuffle ( ) : void
return	void

this() public method

Get chromosome with specified index.

Allows to access individuals of the population.

public this ( int index ) : IChromosome
index	int	Chromosome's index to retrieve.
return	IChromosome