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