Ticket #2319: Grouping Benchmark Problem LLE.cs

using System;
using System.Linq;
using System.Collections.Generic;
using HeuristicLab.Common;
using HeuristicLab.Core;
using HeuristicLab.Data;
using HeuristicLab.Encodings.LinearLinkageEncoding;
using HeuristicLab.Optimization;
using HeuristicLab.Problems.Programmable;

namespace HeuristicLab.Problems.Programmable {
  public class CompiledSingleObjectiveProblemDefinition : CompiledProblemDefinition, ISingleObjectiveProblemDefinition {
    private const int ProblemSize = 100;
    public bool Maximization { get { return false; } }

    private bool[,] allowedTogether;
      
    public override void Initialize() {
      var encoding = new LinearLinkageEncoding("lle", length: ProblemSize);
      allowedTogether = new bool[encoding.Length, encoding.Length];
      var random = new System.Random(13);
      for (var i = 0; i < encoding.Length - 1; i++)
        for (var j = i + 1; j < encoding.Length; j++)
          allowedTogether[i, j] = allowedTogether[j, i] = random.Next(2) == 0;
      
      Encoding = encoding;
    }

    public double Evaluate(Individual individual, IRandom random) {
      var penalty = 0;
      var groups = individual.LinearLinkage("lle").GetGroups().ToList();
      for (var i = 0; i < groups.Count; i++) {
        for (var j = 0; j < groups[i].Count; j++)
          for (var k = j + 1; k < groups[i].Count; k++)
            if (!allowedTogether[groups[i][j], groups[i][k]]) penalty++;
      }
      if (penalty > 0) return penalty + ProblemSize;
      else return groups.Count;
    }

    public void Analyze(Individual[] individuals, double[] qualities, ResultCollection results, IRandom random) { }

    public IEnumerable<Individual> GetNeighbors(Individual individual, IRandom random) {
      foreach (var move in ExhaustiveSwap2MoveGenerator.Generate(individual.LinearLinkage("lle"))) {
        var neighbor = individual.Copy();
        var lle = neighbor.LinearLinkage("lle");
        Swap2MoveMaker.Apply(lle, move);
        yield return neighbor;
      }
    }
  }
}