source: branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/GenotypeToPhenotypeMapper.cs @ 10075

Last change on this file since 10075 was 10075, checked in by sawinkle, 7 years ago

#2109:

  • For each newly created node, ResetLocalParameters() has to be called, if possible. Otherwise 'Variable' symbols won't be initialized correctly. (E.g. internal ValueName is null and causes exceptions.)
  • Method MapDepthFirstRecursively() of DepthFirstMapper.cs checks subtree boundaries by using the MinimumArity instead of the MaximumArity. Otherwise e.g. adding the 'Addition' symbol will cause very short trees, because this symbol has got a MaximumArity of 255! This would cause, that the tree is immediately full, after insertion of one 'Addition' symbol, if the genotype length is e.g. just 100.
  • Several bug fixes.
  • Unresolved issues:
    • Changes in the selected grammar are not taken into account during a run (e.g. 'Addition' symbols will be inserted into the tree, although its checkbox was unchecked previously).
    • Exception, if a division by zero is tried.
    • Wrapping mechanism.
File size: 4.8 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2013 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.Collections.Generic;
23using System.Linq;
24using HeuristicLab.Common;
25using HeuristicLab.Encodings.IntegerVectorEncoding;
26using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
27using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
28using HeuristicLab.Problems.GrammaticalEvolution.Mappers;
29using HeuristicLab.Random;
30
31namespace HeuristicLab.Problems.GrammaticalEvolution {
32  /// <summary>
33  /// GenotypeToPhenotypeMapper
34  /// </summary>
35  public abstract class GenotypeToPhenotypeMapper : IntegerVectorOperator, IGenotypeToPhenotypeMapper {
36
37    [StorableConstructor]
38    protected GenotypeToPhenotypeMapper(bool deserializing) : base(deserializing) { }
39    protected GenotypeToPhenotypeMapper(GenotypeToPhenotypeMapper original, Cloner cloner) : base(original, cloner) { }
40    protected GenotypeToPhenotypeMapper() : base() { }
41
42    public abstract SymbolicExpressionTree Map(ISymbolicExpressionGrammar grammar,
43                                               IntegerVector genotype);
44
45    /// <summary>
46    /// Randomly returns a terminal node for the given <paramref name="parentNode"/>.
47    /// (A terminal has got a minimum and maximum arity of 0.)
48    /// </summary>
49    /// <param name="parentNode">parent node for which a child node is returned randomly</param>
50    /// <param name="grammar">grammar definition to determine the allowed child symbols for parentNode</param>
51    /// <returns>randomly chosen terminal node with arity 0</returns>
52    protected ISymbolicExpressionTreeNode GetRandomTerminalNode(ISymbolicExpressionTreeNode parentNode,
53                                                              ISymbolicExpressionGrammar grammar) {
54      // only select specific symbols, which can be interpreted ...
55      var possibleSymbolsList = (from s in grammar.GetAllowedChildSymbols(parentNode.Symbol)
56                                 where s.InitialFrequency > 0.0
57                                 where s.MaximumArity == 0
58                                 where s.MinimumArity == 0
59                                 select s).ToList();
60      // TODO: Check, if symbol list is empty (no terminal nodes found) - what should happen?
61      var newNode = possibleSymbolsList.SelectRandom(new MersenneTwister()).CreateTreeNode();
62      if (newNode.HasLocalParameters) newNode.ResetLocalParameters(new MersenneTwister());
63      return newNode;
64    }
65
66
67    /// <summary>
68    /// Returns a randomly chosen child node for the given <paramref name="parentNode"/>.
69    /// </summary>
70    /// <param name="parentNode">parent node to find a child node randomly for</param>
71    /// <param name="genotype">integer vector, which should be mapped to a tree</param>
72    /// <param name="grammar">grammar definition used to define the allowed child symbols</param>
73    /// <param name="genotypeIndex">index in the integer vector; can be greater than vector length</param>
74    /// <returns>randomly chosen child node for parentNode</returns>
75    protected ISymbolicExpressionTreeNode GetNewChildNode(ISymbolicExpressionTreeNode parentNode,
76                                                          IntegerVector genotype,
77                                                          ISymbolicExpressionGrammar grammar,
78                                                          int genotypeIndex) {
79
80      // only select specific symbols, which can be interpreted ...
81      IEnumerable<ISymbol> symbolList = (from s in grammar.GetAllowedChildSymbols(parentNode.Symbol)
82                                         where s.InitialFrequency > 0.0
83                                         select s).ToList();
84      int prodRuleCount = symbolList.Count();
85      int prodRuleIndex = genotype[genotypeIndex % genotype.Length] % prodRuleCount;
86
87      var newNode = symbolList.ElementAt(prodRuleIndex).CreateTreeNode();
88      if (newNode.HasLocalParameters) newNode.ResetLocalParameters(new MersenneTwister());
89      return newNode;
90    }
91  }
92}
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