source: branches/ScatterSearch/HeuristicLab.Algorithms.ScatterSearch/3.3/TravelingSalesman/TravelingSalesmanImprovementOperator.cs @ 7786

#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2012 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Encodings.PermutationEncoding;
using HeuristicLab.Operators;
using HeuristicLab.Optimization;
using HeuristicLab.Parameters;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
using HeuristicLab.Problems.TravelingSalesman;

namespace HeuristicLab.Algorithms.ScatterSearch.TravelingSalesman {
  /// <summary>
  /// An operator that improves traveling salesman solutions.
  /// </summary>
  [Item("TravelingSalesmanImprovementOperator", "An operator that improves traveling salesman solutions.")]
  [StorableClass]
  public sealed class TravelingSalesmanImprovementOperator : SingleSuccessorOperator, IImprovementOperator {
    #region Parameter properties
    public ScopeParameter CurrentScopeParameter {
      get { return (ScopeParameter)Parameters["CurrentScope"]; }
    }
    public ILookupParameter<DistanceMatrix> DistanceMatrixParameter {
      get { return (ILookupParameter<DistanceMatrix>)Parameters["DistanceMatrix"]; }
    }
    public ILookupParameter<IEvaluator> EvaluatorParameter {
      get { return (ILookupParameter<IEvaluator>)Parameters["Evaluator"]; }
    }
    public IValueParameter<IntValue> ImprovementAttemptsParameter {
      get { return (IValueParameter<IntValue>)Parameters["ImprovementAttempts"]; }
    }
    public ILookupParameter<IRandom> RandomParameter {
      get { return (ILookupParameter<IRandom>)Parameters["Random"]; }
    }
    public IValueLookupParameter<IItem> TargetParameter {
      get { return (IValueLookupParameter<IItem>)Parameters["Target"]; }
    }
    #endregion

    #region Properties
    public IScope CurrentScope {
      get { return CurrentScopeParameter.ActualValue; }
    }
    public DistanceMatrix DistanceMatrix {
      get { return DistanceMatrixParameter.ActualValue; }
      set { DistanceMatrixParameter.ActualValue = value; }
    }
    public IEvaluator Evaluator {
      get { return EvaluatorParameter.ActualValue; }
      set { EvaluatorParameter.ActualValue = value; }
    }
    public IntValue ImprovementAttempts {
      get { return ImprovementAttemptsParameter.Value; }
      set { ImprovementAttemptsParameter.Value = value; }
    }
    public IRandom Random {
      get { return RandomParameter.ActualValue; }
      set { RandomParameter.ActualValue = value; }
    }
    private IItem Target {
      get { return TargetParameter.ActualValue; }
    }
    #endregion

    [StorableConstructor]
    private TravelingSalesmanImprovementOperator(bool deserializing) : base(deserializing) { }
    private TravelingSalesmanImprovementOperator(TravelingSalesmanImprovementOperator original, Cloner cloner) : base(original, cloner) { }
    public TravelingSalesmanImprovementOperator()
      : base() {
      #region Create parameters
      Parameters.Add(new ScopeParameter("CurrentScope"));
      Parameters.Add(new LookupParameter<DistanceMatrix>("DistanceMatrix"));
      Parameters.Add(new LookupParameter<IEvaluator>("Evaluator"));
      Parameters.Add(new ValueParameter<IntValue>("ImprovementAttempts", new IntValue(100)));
      Parameters.Add(new LookupParameter<IRandom>("Random"));
      Parameters.Add(new ValueLookupParameter<IItem>("Target"));
      #endregion
      TargetParameter.ActualName = "TSPTour"; // temporary solution for the traveling salesman problem
    }

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

    public override IOperation Apply() {
      Permutation currSol = CurrentScope.Variables[TargetParameter.ActualName].Value as Permutation;
      if (currSol.PermutationType != PermutationTypes.RelativeUndirected)
        throw new ArgumentException("Cannot improve solution because the permutation type is not supported.");

      for (int i = 0; i < ImprovementAttempts.Value; i++) {
        int a = Random.Next(currSol.Length);
        int b = Random.Next(currSol.Length);
        double oldFirstEdgeLength = DistanceMatrix[currSol[a], currSol[(a - 1 + currSol.Length) % currSol.Length]];
        double oldSecondEdgeLength = DistanceMatrix[currSol[b], currSol[(b + 1) % currSol.Length]];
        double newFirstEdgeLength = DistanceMatrix[currSol[b], currSol[(a - 1 + currSol.Length) % currSol.Length]];
        double newSecondEdgeLength = DistanceMatrix[currSol[a], currSol[(b + 1 + currSol.Length) % currSol.Length]];
        if (newFirstEdgeLength + newSecondEdgeLength < oldFirstEdgeLength + oldSecondEdgeLength)
          Invert(currSol, a, b);
      }

      return base.Apply();
    }

    private void Invert(Permutation sol, int i, int j) {
      if (i != j)
        for (int a = 0; a < Math.Abs(i - j) / 2; a++)
          if (sol[(i + a) % sol.Length] != sol[(j - a + sol.Length) % sol.Length]) {
            // XOR swap
            sol[(i + a) % sol.Length] ^= sol[(j - a + sol.Length) % sol.Length];
            sol[(j - a + sol.Length) % sol.Length] ^= sol[(i + a) % sol.Length];
            sol[(i + a) % sol.Length] ^= sol[(j - a + sol.Length) % sol.Length];
          }
    }
  }
}