Class GaussianMutation<T extends RealValued>
 java.lang.Object

 org.cicirello.search.operators.reals.GaussianMutation<T>

 Type Parameters:
T
 The specific RealValued type.
 All Implemented Interfaces:
Splittable<MutationOperator<T>>
,MutationOperator<T>
,RealValued
,Copyable<GaussianMutation<T>>
 Direct Known Subclasses:
UndoableGaussianMutation
public class GaussianMutation<T extends RealValued> extends Object implements MutationOperator<T>, RealValued, Copyable<GaussianMutation<T>>
This class implements Gaussian mutation. Gaussian mutation is for mutating floatingpoint values. This class can be used to mutate objects of any of the classes that implement the
RealValued
interface, including both univariate and multivariate function input objects.In a Gaussian mutation, a value v is mutated by adding a randomly generated m such that m is drawn from a Gaussian distribution with mean 0 and standard deviation sigma. It is commonly employed in Evolution Strategies when mutating real valued parameters.
This mutation operator also implements the
RealValued
interface to enable implementation of metaheuristics that mutate their own mutation parameters. That is, you can pass a GaussianMutation object to themutate(T)
method of a GaussianMutation object.To construct a GaussianMutation, you must use one of the factory methods. See the various
createGaussianMutation()
methods.Gaussian mutation was introduced in the following article:
Hinterding, R. 1995. Gaussian mutation and selfadaption for numeric genetic algorithms. In IEEE CEC. IEEE Press. 384–389.


Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description GaussianMutation<T>
copy()
Creates an identical copy of this object.static <T extends RealValued>
GaussianMutation<T>createGaussianMutation()
Creates a Gaussian mutation operator with standard deviation equal to 1.static <T extends RealValued>
GaussianMutation<T>createGaussianMutation(double sigma)
Creates a Gaussian mutation operator.static <T extends RealValued>
GaussianMutation<T>createGaussianMutation(double sigma, double p)
Create a Gaussian mutation operator.static <T extends RealValued>
GaussianMutation<T>createGaussianMutation(double sigma, int k)
Create a Gaussian mutation operator.boolean
equals(Object other)
Indicates whether some other object is equal to this one.double
get(int i)
Accesses the current value of sigma.int
hashCode()
Returns a hash code value for the object.int
length()
Gets the number of parameters.void
mutate(T c)
Mutates a candidate solution to a problem, by randomly modifying its state.void
set(int i, double value)
Sets sigma to a specified value.GaussianMutation<T>
split()
Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms.double[]
toArray(double[] values)
Accesses the current value of sigma as an array.



Method Detail

createGaussianMutation
public static <T extends RealValued> GaussianMutation<T> createGaussianMutation()
Creates a Gaussian mutation operator with standard deviation equal to 1. Type Parameters:
T
 The specific RealValued type. Returns:
 A Gaussian mutation operator.

createGaussianMutation
public static <T extends RealValued> GaussianMutation<T> createGaussianMutation(double sigma)
Creates a Gaussian mutation operator. Type Parameters:
T
 The specific RealValued type. Parameters:
sigma
 The standard deviation of the Gaussian. Returns:
 A Gaussian mutation operator.

createGaussianMutation
public static <T extends RealValued> GaussianMutation<T> createGaussianMutation(double sigma, int k)
Create a Gaussian mutation operator. Type Parameters:
T
 The specific RealValued type. Parameters:
sigma
 The standard deviation of the Gaussian mutation.k
 The number of input variables that themutate(T)
method changes when called. The k input variables are chosen uniformly at random from among all subsets of size k. If there are less than k input variables, then all are mutated. Returns:
 A Gaussian mutation operator
 Throws:
IllegalArgumentException
 if k < 1

createGaussianMutation
public static <T extends RealValued> GaussianMutation<T> createGaussianMutation(double sigma, double p)
Create a Gaussian mutation operator. Type Parameters:
T
 The specific RealValued type. Parameters:
sigma
 The standard deviation of the Gaussian mutation.p
 The probability that themutate(T)
method changes an input variable. If there are n input variables, then n*p input variables will be mutated on average during a single call to themutate(T)
method. Returns:
 A Gaussian mutation operator
 Throws:
IllegalArgumentException
 if p ≤ 0

mutate
public void mutate(T c)
Description copied from interface:MutationOperator
Mutates a candidate solution to a problem, by randomly modifying its state. The mutant that is produced is in the local neighborhood of the original candidate solution. Specified by:
mutate
in interfaceMutationOperator<T extends RealValued>
 Parameters:
c
 The candidate solution subject to the mutation. This method changes the state of c.

split
public GaussianMutation<T> split()
Description copied from interface:Splittable
Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms. The state of the object that is returned may or may not be identical to that of the original. Thus, this is a distinct concept from the functionality of theCopyable
interface. Classes that implement this interface must ensure that the object returned performs the same functionality, and that it does not share any state data that would be either unsafe or inefficient for concurrent access by multiple threads. The split method is allowed to simply return the this reference, provided that it is both safe and efficient for multiple threads to share a single copy of the Splittable object. The intention is to provide a multithreaded search with the capability to provide spawned threads with their own distinct search operators. Such multithreaded algorithms can call the split method for each thread it spawns to generate a functionally identical copy of the operator, but with independent state. Specified by:
split
in interfaceSplittable<T extends RealValued>
 Returns:
 A functionally identical copy of the object, or a reference to this if it is both safe and efficient for multiple threads to share a single instance of this Splittable object.

copy
public GaussianMutation<T> copy()
Creates an identical copy of this object. Specified by:
copy
in interfaceCopyable<T extends RealValued>
 Returns:
 an identical copy of this object

equals
public boolean equals(Object other)
Indicates whether some other object is equal to this one. The objects are equal if they are the same type of operator with the same parameters.

hashCode
public int hashCode()
Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

length
public final int length()
Description copied from interface:RealValued
Gets the number of parameters. Specified by:
length
in interfaceRealValued
 Returns:
 The number of parameters for this function.

get
public final double get(int i)
Accesses the current value of sigma. Specified by:
get
in interfaceRealValued
 Parameters:
i
 Ignored. Returns:
 The current value of sigma.

toArray
public final double[] toArray(double[] values)
Accesses the current value of sigma as an array. This method implemented strictly to meet implementation requirements of RealValued interface. Specified by:
toArray
in interfaceRealValued
 Parameters:
values
 An array to hold the result. If values is null or if values.length is not equal 1, then a new array is constructed for the result. Returns:
 An array containing the current value of sigma.

set
public final void set(int i, double value)
Sets sigma to a specified value. Specified by:
set
in interfaceRealValued
 Parameters:
i
 Ignored.value
 The new value for sigma.

