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source: branches/3040_VectorBasedGP/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/TreeMatching/SymbolicExpressionTreeNodeComparer.cs @ 17460

Last change on this file since 17460 was 17180, checked in by swagner, 5 years ago

#2875: Removed years in copyrights

File size: 2.8 KB
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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 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 HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
24using HEAL.Attic;
25
26namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
27  [StorableType("eabf848e-d10c-499e-8c48-c771232ede0e")]
28  // this comparer considers that a < b if the type of a is "greater" than the type of b, for example:
29  // - A function node is "greater" than a terminal node
30  // - A variable terminal is "greater" than a constant terminal
31  // - used for bringing subtrees to a "canonical" form when the operation allows reordering of arguments
32  public class SymbolicExpressionTreeNodeComparer : ISymbolicExpressionTreeNodeComparer {
33    public static int CompareNodes(ISymbolicExpressionTreeNode a, ISymbolicExpressionTreeNode b) {
34      var ta = a as SymbolicExpressionTreeTerminalNode;
35      var tb = b as SymbolicExpressionTreeTerminalNode;
36
37      if (ta == null)
38        return tb == null ? String.CompareOrdinal(a.Symbol.Name, b.Symbol.Name) : -1;
39
40      if (tb == null)
41        return 1;
42
43      // at this point we know a and b are both terminals
44      var va = a as VariableTreeNode;
45      var vb = b as VariableTreeNode;
46
47      if (va != null)
48        return vb == null ? -1 : CompareVariables(va, vb);
49
50      if (vb != null)
51        return 1;
52
53      // at this point we know a and b are not variables
54      var ca = a as ConstantTreeNode;
55      var cb = b as ConstantTreeNode;
56
57      if (ca != null && cb != null)
58        return ca.Value.CompareTo(cb.Value);
59
60      // for other unknown terminal types, compare strings
61      return string.CompareOrdinal(a.ToString(), b.ToString());
62    }
63
64    private static int CompareVariables(VariableTreeNode a, VariableTreeNode b) {
65      int result = string.CompareOrdinal(a.VariableName, b.VariableName);
66      return result == 0 ? a.Weight.CompareTo(b.Weight) : result;
67    }
68
69    public int Compare(ISymbolicExpressionTreeNode x, ISymbolicExpressionTreeNode y) {
70      return CompareNodes(x, y);
71    }
72  }
73
74}
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