org.moeaframework.core.operator.real
Class PM

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

All Implemented Interfaces:

Variation

public class PM
extends Object
implements Variation

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

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

Method Summary

static void	evolve(RealVariable v, double distributionIndex) Mutates the specified variable using polynomial mutation.
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 controlling the shape of the polynomial mutation.
double	getProbability() Returns the probability this operator is applied to each decision variable.

Methods inherited from class java.lang.Object

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

Constructor Detail

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 Detail

getProbability

public double getProbability()

Returns the probability this operator is applied to each decision variable.

Returns:

the probability this operator is applied to each decision variable

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

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 v,
                          double distributionIndex)

Mutates the specified variable using polynomial mutation.

Parameters:

v - the variable to be mutated

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

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