Module org.cicirello.jpt
Package 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.

  • Constructor Details

    • 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 Details

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