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source: branches/HeuristicLab.TimeSeries/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interpreter/InterpreterState.cs @ 7930

Last change on this file since 7930 was 7930, checked in by mkommend, 12 years ago

#1081: Refactored symbolic expression tree interpreter in preparation for autoregressive single variate prognosis.

File size: 2.8 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 HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
23
24namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
25  internal class InterpreterState {
26    private double[] argumentStack;
27    private int argumentStackPointer;
28    private Instruction[] code;
29    private int pc;
30    public int ProgramCounter {
31      get { return pc; }
32      set { pc = value; }
33    }
34    internal InterpreterState(Instruction[] code, int argumentStackSize) {
35      this.code = code;
36      this.pc = 0;
37      if (argumentStackSize > 0) {
38        this.argumentStack = new double[argumentStackSize];
39      }
40      this.argumentStackPointer = 0;
41    }
42
43    internal void Reset() {
44      this.pc = 0;
45      this.argumentStackPointer = 0;
46    }
47
48    internal Instruction NextInstruction() {
49      return code[pc++];
50    }
51    // skips a whole branch
52    internal void SkipInstructions() {
53      int i = 1;
54      while (i > 0) {
55        i += NextInstruction().nArguments;
56        i--;
57      }
58    }
59
60    private void Push(double val) {
61      argumentStack[argumentStackPointer++] = val;
62    }
63    private double Pop() {
64      return argumentStack[--argumentStackPointer];
65    }
66
67    internal void CreateStackFrame(double[] argValues) {
68      // push in reverse order to make indexing easier
69      for (int i = argValues.Length - 1; i >= 0; i--) {
70        argumentStack[argumentStackPointer++] = argValues[i];
71      }
72      Push(argValues.Length);
73    }
74
75    internal void RemoveStackFrame() {
76      int size = (int)Pop();
77      argumentStackPointer -= size;
78    }
79
80    internal double GetStackFrameValue(ushort index) {
81      // layout of stack:
82      // [0]   <- argumentStackPointer
83      // [StackFrameSize = N + 1]
84      // [Arg0] <- argumentStackPointer - 2 - 0
85      // [Arg1] <- argumentStackPointer - 2 - 1
86      // [...]
87      // [ArgN] <- argumentStackPointer - 2 - N
88      // <Begin of stack frame>
89      return argumentStack[argumentStackPointer - index - 2];
90    }
91  }
92}
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