org.cicirello.permutations.distance

Class CyclicReversalIndependentDistance

java.lang.Object

org.cicirello.permutations.distance.CyclicReversalIndependentDistance

All Implemented Interfaces:

PermutationDistanceMeasurer, PermutationDistanceMeasurerDouble

public final class CyclicReversalIndependentDistance
extends Object
implements PermutationDistanceMeasurer

This class implements the combination of cyclic independence and reversal independence. This is relevant if any rotation of the permutation or its reverse has the same problem dependent interpretation. For example, if the permutation represents a solution to a traveling salesperson problem (i.e. a tour of a set of cities), then the cost of that tour is the same if you rotate it, reverse it, or reverse it and rotate it.

In this case, this class computes the minimum of the distance from permutation p1 to rotations of p2 and rotations of the reverse of p2, where the underlying distance measure is passed as a parameter to the constructor.

Since:

1.0

Constructor Summary

Constructors

Constructor and Description
CyclicReversalIndependentDistance(PermutationDistanceMeasurer d) Constructs a distance measure for measuring distance with cyclic and reversal independence, such that distance = min_{i in [0,N)} { distance(p1,rotate(p2,i)), distance(p1,rotate(reverse(p2),i)) }

Method Summary

Modifier and Type	Method and Description
int	distance(Permutation p1, Permutation p2) Measures the distance between two permutations, with cyclic and reversal independence: distance = min_{i in [0,N)} { distance(p1,rotate(p2,i)), distance(p1,rotate(reverse(p2),i)) }
double	distancef(Permutation p1, Permutation p2) Measures the distance between two permutations

Methods inherited from class java.lang.Object

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

Constructor Detail

CyclicReversalIndependentDistance

public CyclicReversalIndependentDistance(PermutationDistanceMeasurer d)

Constructs a distance measure for measuring distance with cyclic and reversal independence, such that distance = min_{i in [0,N)} { distance(p1,rotate(p2,i)), distance(p1,rotate(reverse(p2),i)) }

Parameters:

d - A distance measure.

Method Detail

distance

public int distance(Permutation p1,
                    Permutation p2)

Measures the distance between two permutations, with cyclic and reversal independence: distance = min_{i in [0,N)} { distance(p1,rotate(p2,i)), distance(p1,rotate(reverse(p2),i)) }

Specified by:

distance in interface PermutationDistanceMeasurer

Parameters:

p1 - first permutation

p2 - second permutation

Returns:

distance between p1 and p2

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