source: branches/2994-AutoDiffForIntervals/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Interpreter/InterpreterBase.cs @ 17303

using System;
using HeuristicLab.Common;
using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;

namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
  public abstract class InterpreterBase<T> where T : IAlgebraicType<T> {
    public struct Instruction {
      public byte opcode;
      public ushort narg;
      public int childIndex;
      public double dblVal;
      public object data; // any kind of data you want to store in instructions
      public T value;
    }

    public T Evaluate(Instruction[] code) {
      for (int i = code.Length - 1; i >= 0; --i) {
        var instr = code[i];
        var c = instr.childIndex;
        var n = instr.narg;

        switch (instr.opcode) {
          case OpCodes.Variable: {
              LoadVariable(instr);
              break;
            }
          case OpCodes.Constant: { break; }  // we initialize constants in Compile. The value never changes afterwards
          case OpCodes.Add: {
              instr.value.Assign(code[c].value);
              for (int j = 1; j < n; ++j) {
                instr.value.Add(code[c + j].value);
              }
              break;
            }

          case OpCodes.Sub: {
              if (n == 1) {
                instr.value.AssignNeg(code[c].value);
              } else {
                instr.value.Assign(code[c].value);
                for (int j = 1; j < n; ++j) {
                  instr.value.Sub(code[c + j].value);
                }
              }
              break;
            }

          case OpCodes.Mul: {
              instr.value.Assign(code[c].value);
              for (int j = 1; j < n; ++j) {
                instr.value.Mul(code[c + j].value);
              }
              break;
            }

          case OpCodes.Div: {
              if (n == 1) {
                instr.value.AssignInv(code[c].value);
              } else {
                instr.value.Assign(code[c].value);
                for (int j = 1; j < n; ++j) {
                  instr.value.Div(code[c + j].value);
                }
              }
              break;
            }
          case OpCodes.Square: {
              instr.value.AssignIntPower(code[c].value, 2);
              break;
            }
          case OpCodes.SquareRoot: {
              instr.value.AssignIntRoot(code[c].value, 2);
              break;
            }
          case OpCodes.Cube: {
              instr.value.AssignIntPower(code[c].value, 3);
              break;
            }
          case OpCodes.CubeRoot: {
              instr.value.AssignIntRoot(code[c].value, 3);
              break;
            }
          case OpCodes.Exp: {
              instr.value.AssignExp(code[c].value);
              break;
            }
          case OpCodes.Log: {
              instr.value.AssignLog(code[c].value);
              break;
            }
          case OpCodes.Sin: {
              instr.value.AssignSin(code[c].value);
              break;
            }
          case OpCodes.Cos: {
              instr.value.AssignCos(code[c].value);
              break;
            }
          case OpCodes.Absolute: {
              instr.value.AssignAbs(code[c].value);
              break;
            }
          case OpCodes.AnalyticQuotient: {
              instr.value.Assign(code[c].value);
              for (int j = 1; j < n; ++j) {
                var t = instr.value.One;
                t.Add(code[c + j].value.Clone().IntPower(2));
                instr.value.Div(t.IntRoot(2));
              }
              break;
            }
          case OpCodes.Tanh: {
              instr.value.AssignTanh(code[c].value);
              break;
            }

          default: throw new ArgumentException($"Unknown opcode {instr.opcode}");
        }
      }
      return code[0].value;
    }

    protected Instruction[] Compile(ISymbolicExpressionTree tree) {
      var root = tree.Root.GetSubtree(0).GetSubtree(0);
      var code = new Instruction[root.GetLength()];
      if (root.SubtreeCount > ushort.MaxValue) throw new ArgumentException("Number of subtrees is too big (>65.535)");
      int c = 1, i = 0;
      foreach (var node in root.IterateNodesBreadth()) {
        if (node.SubtreeCount > ushort.MaxValue) throw new ArgumentException("Number of subtrees is too big (>65.535)");
        code[i] = new Instruction {
          opcode = OpCodes.MapSymbolToOpCode(node),
          narg = (ushort)node.SubtreeCount,
          childIndex = c
        };
        if (node is VariableTreeNode variable) {
          InitializeTerminalInstruction(ref code[i], variable);
        } else if (node is ConstantTreeNode constant) {
          InitializeTerminalInstruction(ref code[i], constant);
        } else {
          InitializeInternalInstruction(ref code[i], node);
        }
        c += node.SubtreeCount;
        ++i;
      }
      return code;
    }

    protected abstract void InitializeTerminalInstruction(ref Instruction instruction, ConstantTreeNode constant);
    protected abstract void InitializeTerminalInstruction(ref Instruction instruction, VariableTreeNode variable);
    protected abstract void InitializeInternalInstruction(ref Instruction instruction, ISymbolicExpressionTreeNode node);

    protected abstract void LoadVariable(Instruction a);

  }
}