org.moeaframework.core.operator.real
Class SBX

java.lang.Object
  org.moeaframework.core.operator.real.SBX

All Implemented Interfaces:

Variation

public class SBX
extends Object
implements Variation

Simulated binary crossover (SBX) operator. SBX attempts to simulate the offspring distribution of binary-encoded single-point crossover on real-valued decision variables. An example of this distribution, which favors offspring nearer to the two parents, is shown below.

The distribution index controls the shape of the offspring distribution. Larger values for the distribution index generates offspring closer to the parents.

This operator is type-safe.

References:

1. Deb, K. and Agrawal, R. B. "Simulated Binary Crossover for Continuous Search Space." Indian Institute of Technology, Kanpur, India. Technical Report No. IITK/ME/SMD-94027, 1994.

Constructor Summary

SBX(double probability, double distributionIndex)
Constructs a SBX operator with the specified probability and distribution index.

Method Summary

static void	evolve(RealVariable v1, RealVariable v2, double distributionIndex) Evolves the specified variables using the SBX operator.
Solution[]	evolve(Solution[] parents) Evolves one or more parent solutions (specified by getArity) and produces one or more child solutions.
int	getArity() Returns the number of solutions that must be supplied to the evolve method.
double	getDistributionIndex() Returns the distribution index of this SBX operator.
double	getProbability() Returns the probability of applying this SBX operator to each variable.

Methods inherited from class java.lang.Object

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

Constructor Detail

SBX

public SBX(double probability,
           double distributionIndex)

Constructs a SBX operator with the specified probability and distribution index.

Parameters:

probability - the probability of applying this SBX operator to each variable

distributionIndex - the distribution index of this SBX operator

Method Detail

getProbability

public double getProbability()

Returns the probability of applying this SBX operator to each variable.

Returns:

the probability of applying this SBX operator to each variable

getDistributionIndex

public double getDistributionIndex()

Returns the distribution index of this SBX operator.

Returns:

the distribution index of this SBX operator

getArity

public int getArity()

Description copied from interface: Variation

Returns the number of solutions that must be supplied to the evolve method.

Specified by:

getArity in interface Variation

Returns:

the number of solutions that must be supplied to the evolve method

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.

Specified by:

evolve in interface Variation

Parameters:

parents - the array of parent solutions

Returns:

an array of child solutions

evolve

public static void evolve(RealVariable v1,
                          RealVariable v2,
                          double distributionIndex)

Evolves the specified variables using the SBX operator.

Parameters:

v1 - the first variable

v2 - the second variable

distributionIndex - the distribution index of this SBX operator