source: trunk/sources/HeuristicLab.RealVector/BlendAlphaCrossover.cs @ 874

#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2008 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 System.Collections.Generic;
using System.Text;
using HeuristicLab.Core;
using HeuristicLab.Data;

namespace HeuristicLab.RealVector {
  public class BlendAlphaCrossover : RealVectorCrossoverBase {
    public override string Description {
      get { return
@"Blend alpha crossover for real vectors. Creates a new offspring by selecting a random value from the interval between the two alleles of the parent solutions. The interval is increased in both directions by the factor alpha.
Please use the operator BoundsChecker if necessary.";
      }
    }

    public BlendAlphaCrossover()
      : base() {
      VariableInfo alphaVarInfo = new VariableInfo("Alpha", "Value for alpha", typeof(DoubleData), VariableKind.In);
      alphaVarInfo.Local = true;
      AddVariableInfo(alphaVarInfo);
      AddVariable(new Variable("Alpha", new DoubleData(0.5)));
    }

    public static double[] Apply(IRandom random, double[] parent1, double[] parent2, double alpha) {
      int length = parent1.Length;
      double[] result = new double[length];
      double cMax = 0, cMin = 0, interval = 0, resMin = 0, resMax = 0;

      for (int i = 0; i < length; i++) {
        cMax = Math.Max(parent1[i], parent2[i]);
        cMin = Math.Min(parent1[i], parent2[i]);
        interval = Math.Abs(cMax - cMin);
        resMin = cMin - interval * alpha;
        resMax = cMax + interval * alpha;

        result[i] = resMin + random.NextDouble() * Math.Abs(resMax - resMin);
      }
      return result;
    }

    protected override double[] Cross(IScope scope, IRandom random, double[] parent1, double[] parent2) {
      double alpha = GetVariableValue<DoubleData>("Alpha", scope, true).Data;
      return Apply(random, parent1, parent2, alpha);
    }
  }
}