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

Class WindowLimitedSwapMutation

java.lang.Object
org.cicirello.search.operators.permutations.SwapMutation
org.cicirello.search.operators.permutations.WindowLimitedSwapMutation
All Implemented Interfaces:
Splittable<MutationOperator<Permutation>>, IterableMutationOperator<Permutation>, MutationOperator<Permutation>, UndoableMutationOperator<Permutation>
public final class WindowLimitedSwapMutation extends SwapMutation
This class implements a window-limited version of the SwapMutation mutation operator on permutations. A window-limited mutation operator on permutations is a mutation operator such that there is a window constraint, w, on the random indexes used by the mutation. For a mutation operator that uses a pair of random indexes, (i, j), these indexes are constrained such that |i-j| ≤ w. All index pairs that satisfy the window constraint are equally likely.

The runtime of both the mutate and undo methods is O(1), since only 2 elements must be moved regardless of permutation length and window limit.

For further discussion of window limited permutation mutation operators see:
V. A. Cicirello, "On the Effects of Window-Limits on the Distance Profiles of Permutation Neighborhood Operators," in Proceedings of the 8th International Conference on Bioinspired Information and Communications Technologies, pages 28–35, December 2014.

  • Constructor Details

    • WindowLimitedSwapMutation

      public WindowLimitedSwapMutation()
      Constructs a WindowLimitedSwapMutation mutation operator with a default window limit of Integer.MAX_VALUE.

    • WindowLimitedSwapMutation

      public WindowLimitedSwapMutation(int windowLimit)
      Constructs a WindowLimitedSwapMutation mutation operator.
      Parameters:
      windowLimit - The window limit, which must be positive.
      Throws:
      IllegalArgumentException - if windowLimit ≤ 0

  • Method Details

    • split

      public WindowLimitedSwapMutation 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 IterableMutationOperator<Permutation>
      Specified by:
      split in interface Splittable<MutationOperator<Permutation>>
      Specified by:
      split in interface UndoableMutationOperator<Permutation>
      Overrides:
      split in class SwapMutation
      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.

    • iterator

      public MutationIterator iterator(Permutation p)
      Description copied from class: SwapMutation
      Creates and returns a MutationIterator that can be used to systematically iterate over all of the direct neighbors (i.e., a single mutation step away) of a candidate solution, as one might do in a hill climber.

      The worst case runtime of the MutationIterator.hasNext(), MutationIterator.nextMutant(), MutationIterator.setSavepoint(), and MutationIterator.rollback() methods of the MutationIterator created by this method is O(1).

      Specified by:
      iterator in interface IterableMutationOperator<Permutation>
      Overrides:
      iterator in class SwapMutation
      Parameters:
      p - The candidate solution subject to the mutation. Calling methods of the MutationIterator that is returned changes the state of that candidate solution. See the documentation of those methods for details of how such changes may occur.
      Returns:
      A MutationIterator for iterating over the direct neighbors of a candidate solution.