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source: branches/GeneralizedQAP/HeuristicLab.Problems.GeneralizedQuadraticAssignment/3.3/SolutionCreators/RandomButFeasibleSolutionCreator.cs @ 7593

Last change on this file since 7593 was 7593, checked in by abeham, 12 years ago

#1614

  • Investigation in different solution creator that result in feasible solutions even for 95% fill level instances
  • Added option for all solution creators to produce the least infeasible solution if no feasible solution could be found
  • Added maximum tries parameter to all creators
File size: 5.3 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2012 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using System.Collections.Generic;
24using System.Linq;
25using System.Threading;
26using HeuristicLab.Common;
27using HeuristicLab.Core;
28using HeuristicLab.Data;
29using HeuristicLab.Encodings.IntegerVectorEncoding;
30using HeuristicLab.Parameters;
31using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
32using HeuristicLab.Problems.GeneralizedQuadraticAssignment.Common;
33
34namespace HeuristicLab.Problems.GeneralizedQuadraticAssignment {
35  [Item("RandomButFeasibleSolutionCreator", "Creates a random, but feasible solution to the Generalized Quadratic Assignment Problem.")]
36  [StorableClass]
37  public class RandomFeasibleSolutionCreator : GQAPStochasticSolutionCreator {
38
39    public IValueLookupParameter<IntValue> MaximumTriesParameter {
40      get { return (IValueLookupParameter<IntValue>)Parameters["MaximumTries"]; }
41    }
42    public IValueLookupParameter<BoolValue> CreateMostFeasibleSolutionParameter {
43      get { return (IValueLookupParameter<BoolValue>)Parameters["CreateMostFeasibleSolution"]; }
44    }
45
46    [StorableConstructor]
47    protected RandomFeasibleSolutionCreator(bool deserializing) : base(deserializing) { }
48    protected RandomFeasibleSolutionCreator(RandomFeasibleSolutionCreator original, Cloner cloner) : base(original, cloner) { }
49    public RandomFeasibleSolutionCreator()
50      : base() {
51      Parameters.Add(new ValueLookupParameter<IntValue>("MaximumTries", "The maximum number of tries to create a feasible solution after which an exception is thrown. If it is set to 0 or a negative value there will be an infinite number of attempts.", new IntValue(100000)));
52      Parameters.Add(new ValueLookupParameter<BoolValue>("CreateMostFeasibleSolution", "If this is set to true the operator will always succeed, and outputs the solution with the least violation instead of throwing an exception.", new BoolValue(false)));
53    }
54
55    public override IDeepCloneable Clone(Cloner cloner) {
56      return new RandomFeasibleSolutionCreator(this, cloner);
57    }
58
59    public static IntegerVector CreateSolution(IRandom random, DoubleArray demands, DoubleArray capacities, int maximumTries, bool createMostFeasibleSolution, CancellationToken cancel) {
60      IntegerVector result = null;
61      bool isFeasible = false;
62      int counter = 0;
63      double minViolation = double.MaxValue;
64      var slack = new DoubleArray(capacities.Length);
65      var assignment = new IntegerVector(demands.Length);
66
67      while (!isFeasible) {
68        cancel.ThrowIfCancellationRequested();
69        if (maximumTries > 0) {
70          counter++;
71          if (counter > maximumTries) {
72            if (createMostFeasibleSolution) break;
73            else throw new InvalidOperationException("A feasible solution could not be obtained after " + maximumTries + " attempts.");
74          }
75        }
76        for (int i = 0; i < capacities.Length; i++) slack[i] = capacities[i];
77        foreach (var equipment in Enumerable.Range(0, demands.Length).Shuffle(random)) {
78          var freeLocations = GetFreeLocations(equipment, demands, slack);
79          assignment[equipment] = freeLocations.ChooseUniformRandom(random);
80          slack[assignment[equipment]] -= demands[equipment];
81        }
82        double violation = GQAPEvaluator.EvaluateOverbooking(slack, capacities);
83        isFeasible = violation == 0;
84        if (isFeasible || violation < minViolation) {
85          result = (IntegerVector)assignment.Clone();
86          minViolation = violation;
87        }
88      }
89      return result;
90    }
91
92    protected override IntegerVector CreateRandomSolution(IRandom random, DoubleArray demands, DoubleArray capacities) {
93      return CreateSolution(random, demands, capacities,
94        MaximumTriesParameter.ActualValue.Value,
95        CreateMostFeasibleSolutionParameter.ActualValue.Value,
96        CancellationToken);
97    }
98
99    private static IEnumerable<int> GetFreeLocations(int equipment, DoubleArray demands, DoubleArray freeCapacities) {
100      var freeLocations = freeCapacities
101        .Select((v, idx) => new KeyValuePair<int, double>(idx, v))
102        .Where(x => x.Value >= demands[equipment]);
103      if (!freeLocations.Any()) {
104        freeLocations = freeCapacities
105          .Select((v, idx) => new KeyValuePair<int, double>(idx, v))
106          .OrderByDescending(x => x.Value)
107          .Take(3); // if there are none, take the three where the free capacity is largest
108      }
109      return freeLocations.Select(x => x.Key);
110    }
111  }
112}
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