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source: stable/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/ArchitectureManipulators/ArgumentDeleter.cs @ 12009

Last change on this file since 12009 was 12009, checked in by ascheibe, 9 years ago

#2212 updated copyright year

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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2015 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.Linq;
23using HeuristicLab.Common;
24using HeuristicLab.Core;
25using HeuristicLab.Data;
26using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
27
28namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
29  /// <summary>
30  /// As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 112
31  /// </summary>
32  [Item("ArgumentDeleter", "Manipulates a symbolic expression by deleting an argument from an existing function defining branch. As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 112")]
33  [StorableClass]
34  public sealed class ArgumentDeleter : SymbolicExpressionTreeArchitectureManipulator {
35    [StorableConstructor]
36    private ArgumentDeleter(bool deserializing) : base(deserializing) { }
37    private ArgumentDeleter(ArgumentDeleter original, Cloner cloner) : base(original, cloner) { }
38    public ArgumentDeleter() : base() { }
39
40    public override sealed void ModifyArchitecture(
41      IRandom random,
42      ISymbolicExpressionTree symbolicExpressionTree,
43      IntValue maxFunctionDefinitions, IntValue maxFunctionArguments) {
44      DeleteArgument(random, symbolicExpressionTree, maxFunctionDefinitions.Value, maxFunctionArguments.Value);
45    }
46
47    public override IDeepCloneable Clone(Cloner cloner) {
48      return new ArgumentDeleter(this, cloner);
49    }
50
51    public static bool DeleteArgument(
52      IRandom random,
53      ISymbolicExpressionTree symbolicExpressionTree,
54      int maxFunctionDefinitions, int maxFunctionArguments) {
55
56      var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>();
57      if (functionDefiningBranches.Count() == 0)
58        // no function defining branch => abort
59        return false;
60      var selectedDefunBranch = functionDefiningBranches.SelectRandom(random);
61      if (selectedDefunBranch.NumberOfArguments <= 1)
62        // argument deletion by consolidation is not possible => abort
63        return false;
64      // the argument to be removed is always the one with the largest index
65      // (otherwise we would have to decrement the index of the larger argument symbols)
66      var removedArgument = (from sym in selectedDefunBranch.Grammar.Symbols.OfType<Argument>()
67                             select sym.ArgumentIndex).Distinct().OrderBy(x => x).Last();
68      // find invocations of the manipulated funcion and remove the specified argument tree
69      var invocationNodes = (from node in symbolicExpressionTree.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>()
70                             where node.Symbol.FunctionName == selectedDefunBranch.FunctionName
71                             select node).ToList();
72      foreach (var invokeNode in invocationNodes) {
73        invokeNode.RemoveSubtree(removedArgument);
74      }
75
76      DeleteArgumentByConsolidation(random, selectedDefunBranch, removedArgument);
77
78      // delete the dynamic argument symbol that matches the argument to be removed
79      var matchingSymbol = selectedDefunBranch.Grammar.Symbols.OfType<Argument>().Where(s => s.ArgumentIndex == removedArgument).Single();
80      selectedDefunBranch.Grammar.RemoveSymbol(matchingSymbol);
81      selectedDefunBranch.NumberOfArguments--;
82      // reduce arity in known functions of all root branches
83      foreach (var subtree in symbolicExpressionTree.Root.Subtrees) {
84        var matchingInvokeSymbol = subtree.Grammar.Symbols.OfType<InvokeFunction>().Where(s => s.FunctionName == selectedDefunBranch.FunctionName).SingleOrDefault();
85        if (matchingInvokeSymbol != null) {
86          subtree.Grammar.SetSubtreeCount(matchingInvokeSymbol, selectedDefunBranch.NumberOfArguments, selectedDefunBranch.NumberOfArguments);
87        }
88      }
89      return true;
90    }
91
92    private static void DeleteArgumentByConsolidation(IRandom random, DefunTreeNode branch, int removedArgumentIndex) {
93      // replace references to the deleted argument with random references to existing arguments
94      var possibleArgumentSymbols = (from sym in branch.Grammar.Symbols.OfType<Argument>()
95                                     where sym.ArgumentIndex != removedArgumentIndex
96                                     select sym).ToList();
97      var argNodes = from node in branch.IterateNodesPrefix().OfType<ArgumentTreeNode>()
98                     where node.Symbol.ArgumentIndex == removedArgumentIndex
99                     select node;
100      foreach (var argNode in argNodes) {
101        var replacementSymbol = possibleArgumentSymbols.SelectRandom(random);
102        argNode.Symbol = replacementSymbol;
103      }
104    }
105  }
106}
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