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source: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/RandomMapper.cs @ 10975

Last change on this file since 10975 was 10975, checked in by gkronber, 10 years ago

#2109 copied grammatical evolution plugin from feature development branch into the trunk

File size: 5.2 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2014 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 * Author: Sabine Winkler
21 */
22#endregion
23
24using System.Collections.Generic;
25using HeuristicLab.Common;
26using HeuristicLab.Core;
27using HeuristicLab.Data;
28using HeuristicLab.Encodings.IntegerVectorEncoding;
29using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
30using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
31
32namespace HeuristicLab.Problems.GrammaticalEvolution {
33  /// <summary>
34  /// RandomMapper
35  /// </summary>
36  [Item("RandomMapper", "Randomly determines the next non-terminal symbol to expand.")]
37  [StorableClass]
38  public class RandomMapper : GenotypeToPhenotypeMapper {
39
40    [StorableConstructor]
41    protected RandomMapper(bool deserializing) : base(deserializing) { }
42    protected RandomMapper(RandomMapper original, Cloner cloner) : base(original, cloner) { }
43    public RandomMapper() : base() { }
44
45    public override IDeepCloneable Clone(Cloner cloner) {
46      return new RandomMapper(this, cloner);
47    }
48
49
50    /// <summary>
51    /// Maps a genotype (an integer vector) to a phenotype (a symbolic expression tree).
52    /// Random approach.
53    /// </summary>
54    /// <param name="random">random number generator</param>
55    /// <param name="bounds">only used for PIGEMapper (ignore here)</param>
56    /// <param name="length">only used for PIGEMapper (ignore here)</param>
57    /// <param name="grammar">grammar definition</param>
58    /// <param name="genotype">integer vector, which should be mapped to a tree</param>
59    /// <returns>phenotype (a symbolic expression tree)</returns>
60    public override SymbolicExpressionTree Map(IRandom random, IntMatrix bounds, int length,
61                                               ISymbolicExpressionGrammar grammar,
62                                               IntegerVector genotype) {
63
64      SymbolicExpressionTree tree = new SymbolicExpressionTree();
65      var rootNode = (SymbolicExpressionTreeTopLevelNode)grammar.ProgramRootSymbol.CreateTreeNode();
66      var startNode = (SymbolicExpressionTreeTopLevelNode)grammar.StartSymbol.CreateTreeNode();
67      rootNode.AddSubtree(startNode);
68      tree.Root = rootNode;
69
70      MapRandomIteratively(startNode, genotype, grammar,
71                           genotype.Length, random);
72
73      return tree;
74    }
75
76
77    /// <summary>
78    /// Genotype-to-Phenotype mapper (iterative random approach, where the next non-terminal
79    /// symbol to expand is randomly determined).
80    /// </summary>
81    /// <param name="startNode">first node of the tree with arity 1</param>
82    /// <param name="genotype">integer vector, which should be mapped to a tree</param>
83    /// <param name="grammar">grammar to determine the allowed child symbols for each node</param>
84    /// <param name="maxSubtreeCount">maximum allowed subtrees (= number of used genomes)</param>
85    /// <param name="random">random number generator</param>
86    private void MapRandomIteratively(ISymbolicExpressionTreeNode startNode,
87                                     IntegerVector genotype,
88                                     ISymbolicExpressionGrammar grammar,
89                                     int maxSubtreeCount, IRandom random) {
90
91      List<ISymbolicExpressionTreeNode> nonTerminals = new List<ISymbolicExpressionTreeNode>();
92
93      int genotypeIndex = 0;
94      nonTerminals.Add(startNode);
95
96      while (nonTerminals.Count > 0) {
97        if (genotypeIndex >= maxSubtreeCount) {
98          // if all genomes were used, only add terminal nodes to the remaining subtrees
99          ISymbolicExpressionTreeNode current = nonTerminals[0];
100          nonTerminals.RemoveAt(0);
101          current.AddSubtree(GetRandomTerminalNode(current, grammar, random));
102        } else {
103          // similar to PIGEMapper, but here the current node is determined randomly ...
104          ISymbolicExpressionTreeNode current = nonTerminals.SelectRandom(random);
105          nonTerminals.Remove(current);
106
107          ISymbolicExpressionTreeNode newNode = GetNewChildNode(current, genotype, grammar, genotypeIndex, random);
108          int arity = SampleArity(random, newNode, grammar);
109
110          current.AddSubtree(newNode);
111          genotypeIndex++;
112          // new node has subtrees, so add "arity" number of copies of this node to the nonTerminals list
113          for (int i = 0; i < arity; ++i) {
114            nonTerminals.Add(newNode);
115          }
116        }
117      }
118    }
119  }
120}
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