source: branches/FitnessLandscapeAnalysis/HeuristicLab.Analysis.FitnessLandscape/DistanceCalculators/PermutationDistanceCalculator.cs @ 7202

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using HeuristicLab.Core;
using HeuristicLab.Common.Resources;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.Common;
using HeuristicLab.Encodings.BinaryVectorEncoding;
using HeuristicLab.Encodings.PermutationEncoding;
using System.Drawing;

namespace HeuristicLab.Analysis.FitnessLandscape.DistanceCalculators {

  [Item("PermutationDistanceCalculator", "Calculates the distance of two permutations")]
  [StorableClass]
  public class PermutationDistanceCalculator : NamedItem, IItemDistanceCalculator {

    #region Properties

    public override bool CanChangeName { get { return false; } }
    public override bool CanChangeDescription { get { return false; } }
    public static new Image StaticItemImage { get { return VSImageLibrary.Function; } }

    #endregion

    #region Construction & Cloning

    [StorableConstructor]
    protected PermutationDistanceCalculator(bool deserializing) : base(deserializing) { }

    protected PermutationDistanceCalculator(PermutationDistanceCalculator original, Cloner cloner)
      : base(original, cloner) {
    }

    public PermutationDistanceCalculator() {
      name = ItemName;
      description = ItemDescription;
    }

    public override IDeepCloneable Clone(Cloner cloner) {
      return new PermutationDistanceCalculator(this, cloner);
    }

    #endregion

    #region IItemDistanceCalculator Members

    public Type ItemType {
      get { return typeof(Permutation); }
    }

    public double Distance(IItem x, IItem y) {
      Permutation a = (Permutation)x;
      Permutation b = (Permutation)y;
      if (a.PermutationType != b.PermutationType)
        throw new InvalidOperationException("Cannot compare two permutations of different type");
      if (a.Length != b.Length)
        throw new InvalidOperationException("Cannot compare vectors of different lengths");
      switch (a.PermutationType) {
        case PermutationTypes.Absolute: return AbsoluteDistance(a, b);
        case PermutationTypes.RelativeDirected: return RelativeDistance(a, b);
        case PermutationTypes.RelativeUndirected: return RelativeDistance(a, b);
        default: throw new NotImplementedException("Unknown permutation type " + a.PermutationType);
      }      
    }

    private double AbsoluteDistance(Permutation a, Permutation b) {
      int mismatches = 0;
      for (int i = 0; i<a.Length; i++) {
        if (a[i] != b[i])
          mismatches++;
      }
      return (double)mismatches;
    }

    private double RelativeDistance(Permutation a, Permutation b) {
      HashSet<Point> edges = new HashSet<Point>();
      for (int i = 0; i < a.Length; i++)
        edges.Add(GetEdge(a, i));
      int nCommonEdges = 0;
      for (int i = 0; i < b.Length; i++) {
        if (edges.Contains(GetEdge(b, i)))
          nCommonEdges++;
      }
      return Math.Max(a.Length, b.Length) - nCommonEdges;
    }

    private static Point GetEdge(Permutation a, int index) {      
      int start = a[index];
      int end = a[(index + 1)%a.Length];
      switch (a.PermutationType) {
        case PermutationTypes.RelativeDirected: return new Point(start, end);
        case PermutationTypes.RelativeUndirected: return new Point(Math.Min(start, end), Math.Max(start, end));
        default: throw new ArgumentException("cannot derive edge from non-relative permutation type");
      }
    }

    #endregion
  }
}