Class UniformScrambleMutation
 java.lang.Object

 org.cicirello.search.operators.permutations.UniformScrambleMutation

 All Implemented Interfaces:
Splittable<MutationOperator<Permutation>>
,MutationOperator<Permutation>
public final class UniformScrambleMutation extends Object implements MutationOperator<Permutation>
This class implements a scramble mutation on permutations, where one mutation consists in randomizing the order of a noncontiguous subset of the permutation elements. It is controlled by a parameter U, which is the probability that an element is included in the scramble. On average, you can expect U*n elements to be randomized, where n is the length of the permutation.
The worst case runtime of the
mutate
method is O(n), and the average case is O(U*n), where n is the length of the permutation.


Constructor Summary
Constructors Constructor Description UniformScrambleMutation(double u)
Constructs a UniformScrambleMutation mutation operator.UniformScrambleMutation(double u, boolean guaranteeChange)
Constructs a UniformScrambleMutation mutation operator.

Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
mutate(Permutation c)
Mutates a candidate solution to a problem, by randomly modifying its state.UniformScrambleMutation
split()
Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms.



Constructor Detail

UniformScrambleMutation
public UniformScrambleMutation(double u)
Constructs a UniformScrambleMutation mutation operator. Parameters:
u
 The probability that an element is included in a scramble. If the permutation length is n, you can expect approximately u*n elements on average to be scrambled. Throws:
IllegalArgumentException
 if u is negative or if u is greater than 1.0.

UniformScrambleMutation
public UniformScrambleMutation(double u, boolean guaranteeChange)
Constructs a UniformScrambleMutation mutation operator. Parameters:
u
 The probability that an element is included in a scramble. If the permutation length is n, you can expect approximately u*n elements on average to be scrambled.guaranteeChange
 If true, then themutate
method will be guaranteed to change the locations of at least 2 elements. Otherwise, if false, it may be possible (e.g., for low values of u) for the mutate method not to change anything during some calls. Throws:
IllegalArgumentException
 if u is negative or if u is greater than 1.0.


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 interfaceMutationOperator<Permutation>
 Parameters:
c
 The candidate solution subject to the mutation. This method changes the state of c.

split
public UniformScrambleMutation 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 interfaceSplittable<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.

