org.cicirello.permutations.distance

Class AcyclicEdgeDistance

java.lang.Object

org.cicirello.permutations.distance.AcyclicEdgeDistance

All Implemented Interfaces:

NormalizedPermutationDistanceMeasurer, NormalizedPermutationDistanceMeasurerDouble, PermutationDistanceMeasurer, PermutationDistanceMeasurerDouble

public final class AcyclicEdgeDistance
extends Object

Acyclic Edge Distance:

Acyclic edge distance treats the permutations as if they represent sets of edges, and counts the number of edges that differ.

Consider the example permutation: [1, 5, 2, 4, 0, 3]. Acyclic edge distance treats this as equivalent to the set of undirected edges: {(1,5), (5,2), (2,4), (4,0), (0,3)}.

E.g., distance between [1, 5, 2, 4, 0, 3] and [ 5, 1, 4, 0, 3, 2] is 2. Why? Well, the first permutation has the edges: {(1,5), (5,2), (2,4), (4,0), (0,3)}. The second has three of these (5,1), which is the same as (1,5) since they are undirected edges, (4,0), and (0,3), but does not include two of the edges: (5,2), (2,4)

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

Acyclic edge distance was first described in:
S. Ronald, "Distance functions for order-based encodings," in Proc. IEEE CEC. IEEE Press, 1997, pp. 49–54.

Since:

1.0

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
int	distance(Permutation p1, Permutation p2) Measures the distance between two permutations.
double	distancef(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.
double	maxf(int length) Computes the maximum possible distance between permutations of a specified length.
double	normalizedDistance(Permutation p1, Permutation p2) Measures the distance between two permutations, normalized to the interval [0.0, 1.0].

Methods inherited from class java.lang.Object

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

Constructor Detail

AcyclicEdgeDistance

public AcyclicEdgeDistance()

Constructs the distance measurer as specified in the class documentation.

Method Detail

distance

public int distance(Permutation p1,
                    Permutation p2)

Measures the distance between two permutations.

Parameters:

p1 - first permutation

p2 - second permutation

Returns:

distance between p1 and p2

max

public int max(int length)

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

Parameters:

length - Permutation length.

Returns:

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

distancef

public final double distancef(Permutation p1,
                              Permutation p2)

Measures the distance between two permutations

Specified by:

distancef in interface PermutationDistanceMeasurerDouble

Parameters:

p1 - first permutation

p2 - second permutation

Returns:

distance between p1 and p2

maxf

public final double maxf(int length)

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

Specified by:

maxf in interface NormalizedPermutationDistanceMeasurerDouble

Parameters:

length - Permutation length.

Returns:

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

normalizedDistance

public final double normalizedDistance(Permutation p1,
                                       Permutation p2)

Measures the distance between two permutations, normalized to the interval [0.0, 1.0].

Specified by:

normalizedDistance in interface NormalizedPermutationDistanceMeasurerDouble

Parameters:

p1 - first permutation

p2 - second permutation

Returns:

distance between p1 and p2 normalized to the interval [0.0, 1.0]