Package org.moeaframework.core.operator.real

Class PM

java.lang.Object

org.moeaframework.core.operator.TypeSafeMutation<RealVariable>

org.moeaframework.core.operator.real.PM

All Implemented Interfaces:

Configurable, Mutation, Variation

public class PM
extends TypeSafeMutation<RealVariable>

Polynomial mutation (PM) operator. PM attempts to simulate the offspring distribution of binary-encoded bit-flip mutation on real-valued decision variables. Similar to SBX, PM favors offspring nearer to the parent.

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

It is recommended each decision variable is mutated with a probability of 1 / L, where L is the number of decision variables. This results in one mutation per offspring on average.

This operator is type-safe.

References:

1. Deb, K. and Goyal, M. "A combined genetic adaptive search (GeneAS) for engineering design." Computer Science and Informatics, 26(4):30-45, 1996.

Constructor Summary

Constructors

Constructor	Description
PM()	Constructs a polynomial mutation operator with the default settings.
PM(double probability, double distributionIndex)	Constructs a polynomial mutation operator with the specified probability and distribution index.

Method Summary

Modifier and Type	Method	Description
double	getDistributionIndex()	Returns the distribution index controlling the shape of the polynomial mutation.
String	getName()	Returns the name of this variation operator.
void	mutate(RealVariable v)	Mutates the specified variable using polynomial mutation.
void	setDistributionIndex(double distributionIndex)	Sets the distribution index controlling the shape of the polynomial mutation.

Methods inherited from class org.moeaframework.core.operator.TypeSafeMutation

getProbability, mutate, setProbability

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

Methods inherited from interface org.moeaframework.core.operator.Mutation

evolve, getArity

Constructor Details

PM

public PM()

Constructs a polynomial mutation operator with the default settings. This includes a mutation probability of 0.1 and a distribution index of 20.0.

PM

public PM(double probability,
 double distributionIndex)

Constructs a polynomial mutation operator with the specified probability and distribution index.

Parameters:

probability - the probability this operator is applied to each decision variable

distributionIndex - the distribution index controlling the shape of the polynomial mutation.

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

getDistributionIndex

public double getDistributionIndex()

Returns the distribution index controlling the shape of the polynomial mutation.

Returns:

the distribution index controlling the shape of the polynomial mutation

setDistributionIndex

public void setDistributionIndex(double distributionIndex)

Sets the distribution index controlling the shape of the polynomial mutation.

Parameters:

distributionIndex - the distribution index controlling the shape of the polynomial mutation

mutate

public void mutate(RealVariable v)

Mutates the specified variable using polynomial mutation.

Specified by:

mutate in class TypeSafeMutation<RealVariable>

Parameters:

v - the variable to be mutated