Module org.cicirello.chips_n_salsa
Package org.cicirello.search.operators.integers

Class UndoableUniformMutation<T extends IntegerValued>

java.lang.Object
org.cicirello.search.operators.integers.UniformMutation<T>
org.cicirello.search.operators.integers.UndoableUniformMutation<T>
Type Parameters:
T - The specific IntegerValued type.
All Implemented Interfaces:
Splittable<MutationOperator<T>>, MutationOperator<T>, UndoableMutationOperator<T>, IntegerValued, Copyable<UniformMutation<T>>
public class UndoableUniformMutation<T extends IntegerValued> extends UniformMutation<T> implements UndoableMutationOperator<T>
This class implements a uniform mutation on integer valued parameters, with support for the undo(T) method. This class can be used to mutate objects of any of the classes that implement the IntegerValued interface, including both univariates and multivariates.

In the form of uniform mutation implemented by this class, a value v is mutated by adding to it a randomly generated integer m such that m is drawn uniformly at random from the interval [-radius, radius].

This mutation operator also implements the IntegerValued interface to enable implementation of metaheuristics that mutate their own mutation parameters. That is, you can pass a UniformMutation object to the mutate(T) method of a UniformMutation object to mutate its radius.

To construct a UniformMutation, you must use one of the factory methods. See the various createUniformMutation(int) methods.

  • Method Details

    • createUniformMutation

      public static <T extends IntegerValued> UndoableUniformMutation<T> createUniformMutation(int radius)
      Creates a Uniform mutation operator that supports the undo operation.
      Type Parameters:
      T - The specific IntegerValued type.
      Parameters:
      radius - The radius parameter of the Uniform.
      Returns:
      A Uniform mutation operator.

    • createUniformMutation

      public static <T extends IntegerValued> UndoableUniformMutation<T> createUniformMutation(int radius, int k)
      Create a Uniform mutation operator that supports the undo operation.
      Type Parameters:
      T - The specific IntegerValued type.
      Parameters:
      radius - The radius parameter of the Uniform 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 Uniform mutation operator
      Throws:
      IllegalArgumentException - if k < 1

    • createUniformMutation

      public static <T extends IntegerValued> UndoableUniformMutation<T> createUniformMutation(int radius, double p)
      Create a Uniform mutation operator that supports the undo operation.
      Type Parameters:
      T - The specific IntegerValued type.
      Parameters:
      radius - The radius parameter of the Uniform 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 Uniform 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 IntegerValued>
      Overrides:
      mutate in class UniformMutation<T extends IntegerValued>
      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 IntegerValued>
      Parameters:
      c - The candidate solution to revert.

    • split

      public UndoableUniformMutation<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 IntegerValued>
      Specified by:
      split in interface UndoableMutationOperator<T extends IntegerValued>
      Overrides:
      split in class UniformMutation<T extends IntegerValued>
      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 UndoableUniformMutation<T> copy()
      Creates an identical copy of this object.
      Specified by:
      copy in interface Copyable<T extends IntegerValued>
      Overrides:
      copy in class UniformMutation<T extends IntegerValued>
      Returns:
      an identical copy of this object

    • equals

      public boolean equals(Object other)
      Description copied from class: UniformMutation
      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.
      Overrides:
      equals in class UniformMutation<T extends IntegerValued>
      Parameters:
      other - the object with which to compare
      Returns:
      true if and only if the objects are equal