Package org.cicirello.search.operators.reals

Class UndoableGaussianMutation<T extends RealValued>

  • Type Parameters:
    T - The specific RealValued type.
    All Implemented Interfaces:
    Splittable<MutationOperator<T>>, MutationOperator<T>, UndoableMutationOperator<T>, RealValued, Copyable<GaussianMutation<T>>
    public class UndoableGaussianMutation<T extends RealValued>
extends GaussianMutation<T>
implements UndoableMutationOperator<T>

    This class implements Gaussian mutation with support for the undo(T) method. Gaussian mutation is for mutating floating-point 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 an UndoableGaussianMutation object to the mutate(T) method of a UndoableGaussianMutation object.

    To construct an UndoableGaussianMutation, 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 self-adaption for numeric genetic algorithms. In IEEE CEC. IEEE Press. 384–389.

    • Method Detail

      • createGaussianMutation

        public static <T extends RealValued> UndoableGaussianMutation<T> createGaussianMutation()
        Creates a Gaussian mutation operator with standard deviation equal to 1 that supports the undo operation.
        Type Parameters:
        T - The specific RealValued type.
        Returns:
        A Gaussian mutation operator.

      • createGaussianMutation

        public static <T extends RealValued> UndoableGaussianMutation<T> createGaussianMutation​(double sigma)
        Creates a Gaussian mutation operator that supports the undo operation.
        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> UndoableGaussianMutation<T> createGaussianMutation​(double sigma,
                                                                                        int k)
        Create a Gaussian mutation operator that supports the undo operation.
        Type Parameters:
        T - The specific RealValued type.
        Parameters:
        sigma - The standard deviation of the Gaussian mutation.
        k - The number of input variables that the mutate(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> UndoableGaussianMutation<T> createGaussianMutation​(double sigma,
                                                                                        double p)
        Create a Gaussian mutation operator that supports the undo operation.
        Type Parameters:
        T - The specific RealValued type.
        Parameters:
        sigma - The standard deviation of the Gaussian mutation.
        p - The probability that the mutate(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 the mutate(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 interface MutationOperator<T extends RealValued>
        Overrides:
        mutate in class GaussianMutation<T extends RealValued>
        Parameters:
        c - The candidate solution subject to the mutation. This method changes the state of c.

      • undo

        public void undo​(T c)
        Description copied from interface: UndoableMutationOperator

        Returns a candidate solution to its previous state prior to the most recent mutation performed.

        For example, consider the following. Let c' be the current state of c. Let c'' be the state of c after mutate(c); If we then call undo(c), the state of c should revert back to c'.

        The behavior of undo is undefined if c is altered by some other process between the calls to mutate and undo. The behavior is also undefined if a different candidate is given to undo then the last given to mutate. For example, if the following two statements are executed, mutate(c); undo(d);, the effect on d is undefined as it wasn't the most recently mutated candidate solution.

        Specified by:
        undo in interface UndoableMutationOperator<T extends RealValued>
        Parameters:
        c - The candidate solution to revert.

      • split

        public UndoableGaussianMutation<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 the Copyable 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 interface Splittable<T extends RealValued>
        Specified by:
        split in interface UndoableMutationOperator<T extends RealValued>
        Overrides:
        split in class GaussianMutation<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.