Package org.moeaframework.core.operator.real

Class SPX

java.lang.Object

org.moeaframework.core.operator.real.MultiParentVariation

org.moeaframework.core.operator.real.SPX

All Implemented Interfaces:

Configurable, Variation

public class SPX
extends MultiParentVariation

Simplex crossover (SPX) operator. SPX is a multiparent operator, allowing a user-defined number of parents and offspring. The parents form a convex hull, called a simplex. Offspring are generated uniformly at random from within the simplex. The expansion rate parameter can be used to expand the size of the simplex beyond the bounds of the parents. For example, the figure below shows three parent points and the offspring distribution, clearly filling an expanded triangular simplex.

References:

1. Tsutsui, S., Yamamura, M., and Higuchi, T., "Multi-parent Recombination with Simplex Crossover in Real Coded Genetic Algorithms," Proceedings of the Genetic and Evolutionary Computation Conference, vol. 1, pp. 657-664, 1999.
2. Higuchi, T., Tsutsui, S., and Yamamura, M., "Theoretical Analysis of Simplex Crossover for Real-Coded Genetic Algorithms," Parallel Problem Solving from Nature PPSN VI, pp. 365-374, 2000.

Field Summary

Fields inherited from class org.moeaframework.core.operator.real.MultiParentVariation

numberOfOffspring, numberOfParents

Constructor Summary

Constructors

Constructor	Description
SPX()	Constructs a SPX operator with default settings, taking 10 parents and producing 2 offspring.
SPX(int numberOfParents, int numberOfOffspring)	Constructs a SPX operator with the specified number of parents and number of offspring.
SPX(int numberOfParents, int numberOfOffspring, double epsilon)	Constructs a simplex operator with the specified number of parents, number of offspring, and expansion rate.

Method Summary

Modifier and Type	Method	Description
Solution[]	evolve(Solution[] parents)	Evolves one or more parent solutions (specified by getArity) and produces one or more child solutions.
double	getEpsilon()	Returns the expansion rate of this operator.
String	getName()	Returns the name of this variation operator.
void	setEpsilon(double epsilon)	Sets the expansion rate of this operator.

Methods inherited from class org.moeaframework.core.operator.real.MultiParentVariation

getArity, getNumberOfOffspring, getNumberOfParents, setNumberOfOffspring, setNumberOfParents

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.moeaframework.core.configuration.Configurable

applyConfiguration, getConfiguration

Constructor Details

SPX

public SPX()

Constructs a SPX operator with default settings, taking 10 parents and producing 2 offspring. The expansion rate is set to sqrt(numberOfParents+1) to preserve the covariance matrix of the population.

SPX

public SPX(int numberOfParents,
 int numberOfOffspring)

Constructs a SPX operator with the specified number of parents and number of offspring. The expansion rate is set to sqrt(numberOfParents+1) to preserve the covariance matrix of the population.

Parameters:

numberOfParents - the number of parents

numberOfOffspring - the number of offspring

SPX

public SPX(int numberOfParents,
 int numberOfOffspring,
 double epsilon)

Constructs a simplex operator with the specified number of parents, number of offspring, and expansion rate.

Parameters:

numberOfParents - the number of parents

numberOfOffspring - the number of offspring

epsilon - the expansion rate

Method Details

getName

public String getName()

Description copied from interface: Variation

Returns the name of this variation operator. This name should also be used as the prefix for any parameters. As such, the name should only contain alphanumeric characters, avoid using whitespace and other symbols.

Returns:

the name of this variation operator

evolve

public Solution[] evolve(Solution[] parents)

Description copied from interface: Variation

Evolves one or more parent solutions (specified by getArity) and produces one or more child solutions. By contract, the parents must not be modified. The copy constructor should be used to create copies of the parents with these copies subsequently modified.

Parameters:

parents - the array of parent solutions

Returns:

an array of child solutions

getEpsilon

public double getEpsilon()

Returns the expansion rate of this operator.

Returns:

the expansion rate

setEpsilon

public void setEpsilon(double epsilon)

Sets the expansion rate of this operator. The recommended default is sqrt(numberOfParents+1).

Parameters:

epsilon - the expansion rate