Class WindowLimitedReversalMutation
 java.lang.Object

 org.cicirello.search.operators.permutations.ReversalMutation

 org.cicirello.search.operators.permutations.WindowLimitedReversalMutation

 All Implemented Interfaces:
Splittable<MutationOperator<Permutation>>
,IterableMutationOperator<Permutation>
,MutationOperator<Permutation>
,UndoableMutationOperator<Permutation>
public final class WindowLimitedReversalMutation extends ReversalMutation
This class implements a windowlimited version of the
ReversalMutation
mutation operator on permutations. A windowlimited 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 ij ≤ w. All index pairs that satisfy the window constraint are equally likely.The runtime (worst case and average case) of both the
mutate
andundo
methods is O(min(n,w)), where n is the length of the permutation. Since chosen indexes can be no more than w positions apart, at most (w+1) elements are moved.For further discussion of window limited permutation mutation operators see:
V. A. Cicirello, "On the Effects of WindowLimits 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 Summary
Constructors Constructor Description WindowLimitedReversalMutation()
Constructs a WindowLimitedReversalMutation mutation operator with a default window limit of Integer.MAX_VALUE.WindowLimitedReversalMutation(int windowLimit)
Constructs a WindowLimitedReversalMutation mutation operator.

Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description MutationIterator
iterator(Permutation p)
Creates and returns aMutationIterator
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.WindowLimitedReversalMutation
split()
Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms.
Methods inherited from class org.cicirello.search.operators.permutations.ReversalMutation
mutate, undo




Constructor Detail

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

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


Method Detail

split
public WindowLimitedReversalMutation 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 interfaceIterableMutationOperator<Permutation>
 Specified by:
split
in interfaceSplittable<MutationOperator<Permutation>>
 Specified by:
split
in interfaceUndoableMutationOperator<Permutation>
 Overrides:
split
in classReversalMutation
 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)
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()
and theMutationIterator.setSavepoint()
methods of theMutationIterator
created by this method is O(1). The amortized runtime of theMutationIterator.nextMutant()
method is O(1). And the worst case runtime of theMutationIterator.rollback()
method is O(min(n,w)), where n is the length of the Permutation, and w is the window limit. Specified by:
iterator
in interfaceIterableMutationOperator<Permutation>
 Overrides:
iterator
in classReversalMutation
 Parameters:
p
 The candidate solution subject to the mutation. Calling methods of theMutationIterator
that is returned changes the state of p. See the documentation of those methods for details of how such changes may occur. Returns:
 A MutationIterator for iterating over the direct neighbors of c.

