Module org.cicirello.jpt

Package org.cicirello.permutations.distance

Class InterchangeDistance

java.lang.Object

org.cicirello.permutations.distance.InterchangeDistance

All Implemented Interfaces:

NormalizedPermutationDistanceMeasurer, NormalizedPermutationDistanceMeasurerDouble, PermutationDistanceMeasurer, PermutationDistanceMeasurerDouble

public final class InterchangeDistance
extends Object
implements NormalizedPermutationDistanceMeasurer

Interchange distance is the minimum number of swaps necessary to transform one permutation into the other.

Interchange distance is computed efficiently by counting the number of permutation cycles between the permutations. A permutation cycle of length k is transformed into k fixed points with k - 1 swaps (a fixed point is a cycle of length 1).

Runtime: O(n), where n is the permutation length.

Computing Interchange distance using cycle lengths is described in:
V.A. Cicirello, "The Permutation in a Haystack Problem and the Calculus of Search Landscapes," IEEE Transactions on Evolutionary Computation, 20(3):434-446, June 2016.

Constructor Summary

Constructors

Constructor	Description
InterchangeDistance()	Constructs the distance measurer as specified in the class documentation.

Method Summary

Modifier and Type	Method	Description
int	distance(Permutation p1, Permutation p2)	Measures the distance between two permutations.
int	max(int length)	Computes the maximum possible distance between permutations of a specified length.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.cicirello.permutations.distance.NormalizedPermutationDistanceMeasurer

maxf, normalizedDistance

Methods inherited from interface org.cicirello.permutations.distance.PermutationDistanceMeasurer

distancef

Constructor Details

InterchangeDistance

public InterchangeDistance()

Constructs the distance measurer as specified in the class documentation.

Method Details

distance

public int distance(Permutation p1,
 Permutation p2)

Measures the distance between two permutations.

Specified by:

distance in interface PermutationDistanceMeasurer

Parameters:

p1 - first permutation

p2 - second permutation

Returns:

distance between p1 and p2

Throws:

IllegalArgumentException - if p1.length() is not equal to p2.length().

max

public int max(int length)

Description copied from interface: NormalizedPermutationDistanceMeasurer

Computes the maximum possible distance between permutations of a specified length.

Specified by:

max in interface NormalizedPermutationDistanceMeasurer

Parameters:

length - Permutation length.

Returns:

the maximum distance between a pair of permutations of the specified length.