org.opt4j.optimizer.ea

Class Spea2

java.lang.Object

org.opt4j.optimizer.ea.Spea2

All Implemented Interfaces:

Selector

public class Spea2
extends Object
implements Selector

The Spea2-Selector is a Java implementation of the SPEA2-MOEA.

The Spea2-Selector will not work properly if the Objectives are not fixed, i.e., the Objectives of an Individual change during the optimization process. This caused by the internal caching of distances, etc. In this case, it is recommended to use the Nsga2.

Author:

lukasiewycz

See Also:

"SPEA2: Improving the Strength Pareto Evolutionary Algorithm For Multiobjective Optimization, Eckart Zitzler, Marco Laumanns, and Lothar Thiele, In Evolutionary Methods for Design, Optimisation, and Control, pages 19–26, 2002."

Constructor Summary

Constructors

Constructor and Description
Spea2(int tournament, Rand random) Constructs a Spea2-Selector.

Method Summary

Modifier and Type	Method and Description
Collection<Individual>	getLames(int lambda, Collection<Individual> population) Selects a subset of lambda Individuals and returns it as a new Collection.
Collection<Individual>	getLamesFromNonDominated(int count) Returns a specific number of lames from the non-dominated Individuals.
Collection<Individual>	getParents(int mu, Collection<Individual> population) Selects a subset of Individuals and returns it as a new Collection.
void	init(int maxsize) Sets the maximal number of Individuals.

Methods inherited from class java.lang.Object

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

Constructor Detail

Spea2

@Inject
public Spea2(int tournament,
                     Rand random)

Constructs a Spea2-Selector.

Parameters:

tournament - the number of individuals that fight against each other to become a parent

random - the random number generator

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 lambda,
                                       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:

lambda - the number of lames to select

population - the list of individuals

Returns:

the worst lambda individuals

getLamesFromNonDominated

public Collection<Individual> getLamesFromNonDominated(int count)

Returns a specific number of lames from the non-dominated Individuals.

Parameters:

count - the specified number

Returns:

a collection of the lame individuals