Class CyclicEdgeDistance

  • All Implemented Interfaces:
    NormalizedPermutationDistanceMeasurer, NormalizedPermutationDistanceMeasurerDouble, PermutationDistanceMeasurer, PermutationDistanceMeasurerDouble

    public final class CyclicEdgeDistance
    extends Object
    Cyclic Edge Distance:

    Cyclic edge distance treats the permutations as if they represent sets of edges, and counts the number of edges that differ. It treats the last to the first element as an edge.

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

    E.g., distance between [1, 5, 2, 4, 0, 3] and [ 5, 1, 4, 0, 3, 2] is 3. Why? Well, the first permutation has the edges: {(1,5), (5,2), (2,4), (4,0), (0,3), (3,1)}. 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 3 of the edges: (5,2), (2,4), (3,1)

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

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

    • Constructor Detail

      • CyclicEdgeDistance

        public CyclicEdgeDistance()
        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
        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.
        Parameters:
        length - Permutation length.
        Returns:
        the maximum distance between a pair of permutations of the specified length.