Package org.cicirello.search.operators.permutations

Class ScrambleMutation

  • All Implemented Interfaces:
    Splittable<MutationOperator<Permutation>>, MutationOperator<Permutation>
    Direct Known Subclasses:
    WindowLimitedScrambleMutation
    public class ScrambleMutation
extends Object
implements MutationOperator<Permutation>

    This class implements a scramble mutation on permutations, where one mutation consists in randomizing the order of a randomly selected subpermutation. The pair of indexes that indicate the subpermutation to scramble is chosen uniformly at random from among all n(n-1)/2 possible pairs of indexes, where n is the length of the permutation.

    The runtime (worst case and average case) of the mutate method is O(n), where n is the length of the permutation. The worst case runtime occurs when the random indexes are the two end points. On average, a scramble mutation moves approximately n/3 elements.

    • Constructor Detail

      • ScrambleMutation

        public ScrambleMutation()
        Constructs a ScrambleMutation mutation operator.

    • Method Detail

      • mutate

        public final void mutate​(Permutation 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<Permutation>
        Parameters:
        c - The candidate solution subject to the mutation. This method changes the state of c.

      • split

        public ScrambleMutation 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<MutationOperator<Permutation>>
        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.