Package org.opt4j.optimizer.ea

Class Nsga2

java.lang.Object

org.opt4j.optimizer.ea.Nsga2

All Implemented Interfaces:

Selector

Direct Known Subclasses:

SelectorDefault

public class Nsga2
extends Object
implements Selector

The Nsga2 Selector.

See Also:

Nsga2Module, "A Fast Elitist Non-Dominated Sorting Genetic Algorithm for Multi-Objective Optimization: NSGA-II, K. Deb, Samir Agrawal, Amrit Pratap, and T. Meyarivan, Parallel MockProblem Solving from Nature, 2000"

Field Summary

Fields

Modifier and Type	Field	Description
protected FrontDensityIndicator	indicator
protected Random	random
protected int	tournament

Constructor Summary

Constructors

Constructor	Description
Nsga2(Rand random, int tournament, FrontDensityIndicator indicator)	Constructs a Nsga2 Selector.

Method Summary

Modifier and Type	Method	Description
List<List<Individual>>	fronts(Collection<Individual> individuals)	Evaluate the fronts and set the correspondent rank values.
Collection<Individual>	getLames(int n, Collection<Individual> population)	Selects a subset of lambda Individuals and returns it as a new Collection.
Collection<Individual>	getParents(int mu, Collection<Individual> population)	Selects a subset of Individuals and returns it as a new Collection.
protected Map<Individual,Integer>	getRank(List<List<Individual>> fronts)	Determine the ranks of fronts.
void	init(int maxsize)	Sets the maximal number of Individuals.

Methods inherited from class java.lang.Object

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

Field Detail

random

protected final Random random

tournament

protected final int tournament

indicator

protected final FrontDensityIndicator indicator

Constructor Detail

Nsga2

@Inject
public Nsga2(Rand random,
             int tournament,
             FrontDensityIndicator indicator)

Constructs a Nsga2 Selector.

Parameters:

random - the random number generator

tournament - the tournament value

Method Detail

init

public void init(int maxsize)

Description copied from interface: Selector

Sets the maximal number of Individuals.

Specified by:

init in interface Selector

Parameters:

maxsize - the number of individuals

getParents

public Collection<Individual> getParents(int mu,
                                         Collection<Individual> population)

Description copied from interface: Selector

Selects a subset of Individuals and returns it as a new Collection. These so called parents can be used to form the next generation.

Specified by:

getParents in interface Selector

Parameters:

mu - the number of parents to select

population - the list of individuals

Returns:

the parents

getLames

public Collection<Individual> getLames(int n,
                                       Collection<Individual> population)

Description copied from interface: Selector

Selects a subset of lambda Individuals and returns it as a new Collection. These individuals can be erased in the next generation.

Specified by:

getLames in interface Selector

Parameters:

n - the number of lames to select

population - the list of individuals

Returns:

the worst lambda individuals

getRank

protected Map<Individual,Integer> getRank(List<List<Individual>> fronts)

Determine the ranks of fronts.

Parameters:

fronts - the fronts

Returns:

the ranks

fronts

public List<List<Individual>> fronts(Collection<Individual> individuals)

Evaluate the fronts and set the correspondent rank values.

Parameters:

individuals - the individuals

Returns:

the fronts