C# ISymbolicExpressionTree.IterateNodesPrefix方法代码示例

    public static Instruction[] Compile(ISymbolicExpressionTree tree, Func<ISymbolicExpressionTreeNode, byte> opCodeMapper, IEnumerable<Func<Instruction, Instruction>> postInstructionCompiledHooks) {
      Dictionary<string, ushort> entryPoint = new Dictionary<string, ushort>();
      List<Instruction> code = new List<Instruction>();
      // compile main body branches
      foreach (var branch in tree.Root.GetSubtree(0).Subtrees) {
        code.AddRange(Compile(branch, opCodeMapper, postInstructionCompiledHooks));
      }
      // compile function branches
      var functionBranches = from node in tree.IterateNodesPrefix()
                             where node.Symbol is Defun
                             select node;
      foreach (DefunTreeNode branch in functionBranches) {
        if (code.Count > ushort.MaxValue) throw new ArgumentException("Code for the tree is too long (> ushort.MaxValue).");
        entryPoint[branch.FunctionName] = (ushort)code.Count;
        code.AddRange(Compile(branch.GetSubtree(0), opCodeMapper, postInstructionCompiledHooks));
      }
      // address of all functions is fixed now
      // iterate through code again and fill in the jump locations
      for (int i = 0; i < code.Count; i++) {
        Instruction instr = code[i];
        if (instr.dynamicNode.Symbol is InvokeFunction) {
          var invokeNode = (InvokeFunctionTreeNode)instr.dynamicNode;
          instr.data = entryPoint[invokeNode.Symbol.FunctionName];
        }
      }

      return code.ToArray();
    }

    public static bool DeleteSubroutine(
      IRandom random,
      ISymbolicExpressionTree symbolicExpressionTree,
      int maxFunctionDefinitions, int maxFunctionArguments) {
      var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>().ToList();

      if (!functionDefiningBranches.Any())
        // no ADF to delete => abort
        return false;

      var selectedDefunBranch = functionDefiningBranches.SampleRandom(random);
      // remove the selected defun
      int defunSubtreeIndex = symbolicExpressionTree.Root.IndexOfSubtree(selectedDefunBranch);
      symbolicExpressionTree.Root.RemoveSubtree(defunSubtreeIndex);

      // remove references to deleted function
      foreach (var subtree in symbolicExpressionTree.Root.Subtrees.OfType<SymbolicExpressionTreeTopLevelNode>()) {
        var matchingInvokeSymbol = (from symb in subtree.Grammar.Symbols.OfType<InvokeFunction>()
                                    where symb.FunctionName == selectedDefunBranch.FunctionName
                                    select symb).SingleOrDefault();
        if (matchingInvokeSymbol != null) {
          subtree.Grammar.RemoveSymbol(matchingInvokeSymbol);
        }
      }

      DeletionByRandomRegeneration(random, symbolicExpressionTree, selectedDefunBranch);
      return true;
    }

    public static bool DeleteArgument(
      IRandom random,
      ISymbolicExpressionTree symbolicExpressionTree,
      int maxFunctionDefinitions, int maxFunctionArguments) {

      var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>().ToList();
      if (!functionDefiningBranches.Any())
        // no function defining branch => abort
        return false;

      var selectedDefunBranch = functionDefiningBranches.SampleRandom(random);
      if (selectedDefunBranch.NumberOfArguments <= 1)
        // argument deletion by consolidation is not possible => abort
        return false;
      // the argument to be removed is always the one with the largest index 
      // (otherwise we would have to decrement the index of the larger argument symbols)
      var removedArgument = (from sym in selectedDefunBranch.Grammar.Symbols.OfType<Argument>()
                             select sym.ArgumentIndex).Distinct().OrderBy(x => x).Last();
      // find invocations of the manipulated funcion and remove the specified argument tree
      var invocationNodes = (from node in symbolicExpressionTree.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>()
                             where node.Symbol.FunctionName == selectedDefunBranch.FunctionName
                             select node).ToList();
      foreach (var invokeNode in invocationNodes) {
        invokeNode.RemoveSubtree(removedArgument);
      }

      DeleteArgumentByConsolidation(random, selectedDefunBranch, removedArgument);

      // delete the dynamic argument symbol that matches the argument to be removed
      var matchingSymbol = selectedDefunBranch.Grammar.Symbols.OfType<Argument>().Single(s => s.ArgumentIndex == removedArgument);
      selectedDefunBranch.Grammar.RemoveSymbol(matchingSymbol);
      selectedDefunBranch.NumberOfArguments--;
      // reduce arity in known functions of all root branches
      foreach (var subtree in symbolicExpressionTree.Root.Subtrees) {
        var matchingInvokeSymbol = subtree.Grammar.Symbols.OfType<InvokeFunction>().SingleOrDefault(s => s.FunctionName == selectedDefunBranch.FunctionName);
        if (matchingInvokeSymbol != null) {
          subtree.Grammar.SetSubtreeCount(matchingInvokeSymbol, selectedDefunBranch.NumberOfArguments, selectedDefunBranch.NumberOfArguments);
        }
      }
      return true;
    }

 private void CalculateVariableMapping(ISymbolicExpressionTree tree, IDataset dataset) {
   int columnIndex = 0;
   int inputIndex = 0;
   var usedVariables = tree.IterateNodesPrefix().OfType<VariableTreeNode>().Select(v => v.VariableName).Distinct();
   foreach (var variable in dataset.VariableNames) {
     columnIndex++;
     if (!usedVariables.Contains(variable)) continue;
     inputIndex++;
     variableNameMapping[variable] = GetExcelColumnName(inputIndex);
   }
 }

    public static bool DuplicateSubroutine(
      IRandom random,
      ISymbolicExpressionTree symbolicExpressionTree,
      int maxFunctionDefinitions, int maxFunctionArguments) {
      var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>().ToList();
      if (!functionDefiningBranches.Any() || functionDefiningBranches.Count() == maxFunctionDefinitions)
        // no function defining branches to duplicate or already reached the max number of ADFs
        return false;

      string formatString = new StringBuilder().Append('0', (int)Math.Log10(maxFunctionDefinitions) + 1).ToString(); // >= 100 functions => ###
      var allowedFunctionNames = from index in Enumerable.Range(0, maxFunctionDefinitions)
                                 select "ADF" + index.ToString(formatString);

      var selectedBranch = functionDefiningBranches.SampleRandom(random);
      var duplicatedDefunBranch = (DefunTreeNode)selectedBranch.Clone();
      string newFunctionName = allowedFunctionNames.Except(UsedFunctionNames(symbolicExpressionTree)).First();
      duplicatedDefunBranch.FunctionName = newFunctionName;
      symbolicExpressionTree.Root.AddSubtree(duplicatedDefunBranch);
      duplicatedDefunBranch.SetGrammar((ISymbolicExpressionTreeGrammar)selectedBranch.Grammar.Clone());

      var allowedChildSymbols = selectedBranch.Grammar.GetAllowedChildSymbols(selectedBranch.Symbol);
      foreach (var allowedChildSymbol in allowedChildSymbols)
        duplicatedDefunBranch.Grammar.AddAllowedChildSymbol(duplicatedDefunBranch.Symbol, allowedChildSymbol);
      var maxSubtrees = selectedBranch.Grammar.GetMaximumSubtreeCount(selectedBranch.Symbol);
      for (int i = 0; i < maxSubtrees; i++) {
        foreach (var allowedChildSymbol in selectedBranch.Grammar.GetAllowedChildSymbols(selectedBranch.Symbol, i))
          duplicatedDefunBranch.Grammar.AddAllowedChildSymbol(duplicatedDefunBranch.Symbol, allowedChildSymbol);
      }

      // add an invoke symbol for each branch that is allowed to invoke the original function
      foreach (var subtree in symbolicExpressionTree.Root.Subtrees.OfType<SymbolicExpressionTreeTopLevelNode>()) {
        var matchingInvokeSymbol = (from symb in subtree.Grammar.Symbols.OfType<InvokeFunction>()
                                    where symb.FunctionName == selectedBranch.FunctionName
                                    select symb).SingleOrDefault();
        if (matchingInvokeSymbol != null) {
          var invokeSymbol = new InvokeFunction(duplicatedDefunBranch.FunctionName);
          subtree.Grammar.AddSymbol(invokeSymbol);
          subtree.Grammar.SetSubtreeCount(invokeSymbol, duplicatedDefunBranch.NumberOfArguments, duplicatedDefunBranch.NumberOfArguments);

          foreach (ISymbol symbol in subtree.Grammar.Symbols) {
            if (subtree.Grammar.IsAllowedChildSymbol(symbol, matchingInvokeSymbol))
              subtree.Grammar.AddAllowedChildSymbol(symbol, invokeSymbol);
            else {
              for (int i = 0; i < subtree.Grammar.GetMaximumSubtreeCount(symbol); i++)
                if (subtree.Grammar.IsAllowedChildSymbol(symbol, matchingInvokeSymbol, i))
                  subtree.Grammar.AddAllowedChildSymbol(symbol, invokeSymbol, i);
            }
          }

          foreach (ISymbol symbol in subtree.Grammar.GetAllowedChildSymbols(matchingInvokeSymbol))
            if (symbol != invokeSymbol) //avoid duplicate entry invokesymbol / invokesymbol
              subtree.Grammar.AddAllowedChildSymbol(invokeSymbol, symbol);
          for (int i = 0; i < subtree.Grammar.GetMaximumSubtreeCount(matchingInvokeSymbol); i++) {
            foreach (ISymbol symbol in subtree.Grammar.GetAllowedChildSymbols(matchingInvokeSymbol, i).Except(subtree.Grammar.GetAllowedChildSymbols(matchingInvokeSymbol)))
              subtree.Grammar.AddAllowedChildSymbol(invokeSymbol, symbol, i);
          }
        }
        // in the current subtree:
        // for all invoke nodes of the original function replace the invoke of the original function with an invoke of the new function randomly
        var originalFunctionInvocations = from node in subtree.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>()
                                          where node.Symbol.FunctionName == selectedBranch.FunctionName
                                          select node;
        foreach (var originalFunctionInvokeNode in originalFunctionInvocations) {
          var newInvokeSymbol = (from symb in subtree.Grammar.Symbols.OfType<InvokeFunction>()
                                 where symb.FunctionName == duplicatedDefunBranch.FunctionName
                                 select symb).Single();
          // flip coin wether to replace with newly defined function
          if (random.NextDouble() < 0.5) {
            originalFunctionInvokeNode.Symbol = newInvokeSymbol;
          }
        }
      }
      return true;
    }

 private static IEnumerable<string> UsedFunctionNames(ISymbolicExpressionTree symbolicExpressionTree) {
   return from node in symbolicExpressionTree.IterateNodesPrefix()
          where node.Symbol is Defun
          select ((DefunTreeNode)node).FunctionName;
 }

    public static bool CreateSubroutine(
      IRandom random,
      ISymbolicExpressionTree symbolicExpressionTree,
      int maxTreeLength, int maxTreeDepth,
      int maxFunctionDefinitions, int maxFunctionArguments) {
      var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>();
      if (functionDefiningBranches.Count() >= maxFunctionDefinitions)
        // allowed maximum number of ADF reached => abort
        return false;
      if (symbolicExpressionTree.Length + 4 > maxTreeLength)
        // defining a new function causes an length increase by 4 nodes (max) if the max tree length is reached => abort
        return false;
      string formatString = new StringBuilder().Append('0', (int)Math.Log10(maxFunctionDefinitions * 10 - 1)).ToString(); // >= 100 functions => ###
      var allowedFunctionNames = from index in Enumerable.Range(0, maxFunctionDefinitions)
                                 select "ADF" + index.ToString(formatString);

      // select a random body (either the result producing branch or an ADF branch)
      var bodies = from node in symbolicExpressionTree.Root.Subtrees
                   select new { Tree = node, Length = node.GetLength() };
      var totalNumberOfBodyNodes = bodies.Select(x => x.Length).Sum();
      int r = random.Next(totalNumberOfBodyNodes);
      int aggregatedNumberOfBodyNodes = 0;
      ISymbolicExpressionTreeNode selectedBody = null;
      foreach (var body in bodies) {
        aggregatedNumberOfBodyNodes += body.Length;
        if (aggregatedNumberOfBodyNodes > r)
          selectedBody = body.Tree;
      }
      // sanity check
      if (selectedBody == null) throw new InvalidOperationException();

      // select a random cut point in the selected branch
      var allCutPoints = (from parent in selectedBody.IterateNodesPrefix()
                          from subtree in parent.Subtrees
                          select new CutPoint(parent, subtree)).ToList();
      if (!allCutPoints.Any())
        // no cut points => abort
        return false;
      string newFunctionName = allowedFunctionNames.Except(functionDefiningBranches.Select(x => x.FunctionName)).First();
      var selectedCutPoint = allCutPoints.SampleRandom(random);

      // select random branches as argument cut-off points (replaced by argument terminal nodes in the function)
      List<CutPoint> argumentCutPoints = SelectRandomArgumentBranches(selectedCutPoint.Child, random, ARGUMENT_CUTOFF_PROBABILITY, maxFunctionArguments);
      ISymbolicExpressionTreeNode functionBody = selectedCutPoint.Child;
      // disconnect the function body from the tree
      selectedCutPoint.Parent.RemoveSubtree(selectedCutPoint.ChildIndex);
      // disconnect the argument branches from the function
      functionBody = DisconnectBranches(functionBody, argumentCutPoints);
      // insert a function invocation symbol instead
      var invokeNode = (InvokeFunctionTreeNode)(new InvokeFunction(newFunctionName)).CreateTreeNode();
      selectedCutPoint.Parent.InsertSubtree(selectedCutPoint.ChildIndex, invokeNode);
      // add the branches selected as argument as subtrees of the function invocation node
      foreach (var argumentCutPoint in argumentCutPoints)
        invokeNode.AddSubtree(argumentCutPoint.Child);

      // insert a new function defining branch
      var defunNode = (DefunTreeNode)(new Defun()).CreateTreeNode();
      defunNode.FunctionName = newFunctionName;
      defunNode.AddSubtree(functionBody);
      symbolicExpressionTree.Root.AddSubtree(defunNode);
      // the grammar in the newly defined function is a clone of the grammar of the originating branch
      defunNode.SetGrammar((ISymbolicExpressionTreeGrammar)selectedBody.Grammar.Clone());

      var allowedChildSymbols = selectedBody.Grammar.GetAllowedChildSymbols(selectedBody.Symbol);
      foreach (var allowedChildSymbol in allowedChildSymbols)
        defunNode.Grammar.AddAllowedChildSymbol(defunNode.Symbol, allowedChildSymbol);
      var maxSubtrees = selectedBody.Grammar.GetMaximumSubtreeCount(selectedBody.Symbol);
      for (int i = 0; i < maxSubtrees; i++) {
        foreach (var allowedChildSymbol in selectedBody.Grammar.GetAllowedChildSymbols(selectedBody.Symbol, i))
          defunNode.Grammar.AddAllowedChildSymbol(defunNode.Symbol, allowedChildSymbol);
      }

      // remove all argument symbols from grammar except that one contained in cutpoints
      var oldArgumentSymbols = selectedBody.Grammar.Symbols.OfType<Argument>().ToList();
      foreach (var oldArgSymb in oldArgumentSymbols)
        defunNode.Grammar.RemoveSymbol(oldArgSymb);
      // find unique argument indexes and matching symbols in the function defining branch 
      var newArgumentIndexes = (from node in defunNode.IterateNodesPrefix().OfType<ArgumentTreeNode>()
                                select node.Symbol.ArgumentIndex).Distinct();
      // add argument symbols to grammar of function defining branch
      GrammarModifier.AddArgumentSymbol(selectedBody.Grammar, defunNode.Grammar, newArgumentIndexes, argumentCutPoints);
      defunNode.NumberOfArguments = newArgumentIndexes.Count();
      if (defunNode.NumberOfArguments != argumentCutPoints.Count) throw new InvalidOperationException();
      // add invoke symbol for newly defined function to the original branch 
      GrammarModifier.AddInvokeSymbol(selectedBody.Grammar, defunNode.FunctionName, defunNode.NumberOfArguments, selectedCutPoint, argumentCutPoints);

      // when the new function body was taken from another function definition
      // add invoke symbol for newly defined function to all branches that are allowed to invoke the original branch
      if (selectedBody.Symbol is Defun) {
        var originalFunctionDefinition = selectedBody as DefunTreeNode;
        foreach (var subtree in symbolicExpressionTree.Root.Subtrees) {
          var originalBranchInvokeSymbol = (from symb in subtree.Grammar.Symbols.OfType<InvokeFunction>()
                                            where symb.FunctionName == originalFunctionDefinition.FunctionName
                                            select symb).SingleOrDefault();
          // when the original branch can be invoked from the subtree then also allow invocation of the function
          if (originalBranchInvokeSymbol != null) {
            GrammarModifier.AddInvokeSymbol(subtree.Grammar, defunNode.FunctionName, defunNode.NumberOfArguments, selectedCutPoint, argumentCutPoints);
          }
        }
      }
//.........这里部分代码省略.........

    public static bool DuplicateArgument(
      IRandom random,
      ISymbolicExpressionTree symbolicExpressionTree,
      int maxFunctionDefinitions, int maxFunctionArguments) {
      var functionDefiningBranches = symbolicExpressionTree.IterateNodesPrefix().OfType<DefunTreeNode>().ToList();

      var allowedArgumentIndexes = Enumerable.Range(0, maxFunctionArguments);
      if (!functionDefiningBranches.Any())
        // no function defining branches => abort
        return false;

      var selectedDefunBranch = functionDefiningBranches.SampleRandom(random);

      var argumentSymbols = selectedDefunBranch.Grammar.Symbols.OfType<Argument>().ToList();
      if (!argumentSymbols.Any() || argumentSymbols.Count() >= maxFunctionArguments)
        // when no argument or number of arguments is already at max allowed value => abort
        return false;

      var selectedArgumentSymbol = argumentSymbols.SampleRandom(random);
      var takenIndexes = argumentSymbols.Select(s => s.ArgumentIndex);
      var newArgumentIndex = allowedArgumentIndexes.Except(takenIndexes).First();

      var newArgSymbol = new Argument(newArgumentIndex);

      // replace existing references to the original argument with references to the new argument randomly in the selectedBranch
      var argumentNodes = selectedDefunBranch.IterateNodesPrefix().OfType<ArgumentTreeNode>();
      foreach (var argNode in argumentNodes) {
        if (argNode.Symbol == selectedArgumentSymbol) {
          if (random.NextDouble() < 0.5) {
            argNode.Symbol = newArgSymbol;
          }
        }
      }
      // find invocations of the functions and duplicate the matching argument branch
      var invocationNodes = (from node in symbolicExpressionTree.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>()
                             where node.Symbol.FunctionName == selectedDefunBranch.FunctionName
                             where node.Subtrees.Count() == selectedDefunBranch.NumberOfArguments
                             select node).ToList();
      // do this repeatedly until no matching invocations are found      
      while (invocationNodes.Count() > 0) {
        List<ISymbolicExpressionTreeNode> newlyAddedBranches = new List<ISymbolicExpressionTreeNode>();
        foreach (var invokeNode in invocationNodes) {
          // check that the invocation node really has the correct number of arguments
          if (invokeNode.Subtrees.Count() != selectedDefunBranch.NumberOfArguments) throw new InvalidOperationException();
          var argumentBranch = invokeNode.GetSubtree(selectedArgumentSymbol.ArgumentIndex);
          var clonedArgumentBranch = (ISymbolicExpressionTreeNode)argumentBranch.Clone();
          invokeNode.InsertSubtree(newArgumentIndex, clonedArgumentBranch);
          newlyAddedBranches.Add(clonedArgumentBranch);
        }
        invocationNodes = (from newlyAddedBranch in newlyAddedBranches
                           from node in newlyAddedBranch.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>()
                           where node.Symbol.FunctionName == selectedDefunBranch.FunctionName
                           where node.Subtrees.Count() == selectedDefunBranch.NumberOfArguments
                           select node).ToList();
      }
      // register the new argument symbol and increase the number of arguments of the ADF
      selectedDefunBranch.Grammar.AddSymbol(newArgSymbol);
      selectedDefunBranch.Grammar.SetSubtreeCount(newArgSymbol, 0, 0);
      // allow the duplicated argument as child of all other arguments where the orginal argument was allowed
      GrammarModifier.SetAllowedParentSymbols(selectedDefunBranch.Grammar, selectedArgumentSymbol, newArgSymbol);
      selectedDefunBranch.NumberOfArguments++;

      // increase the arity of the changed ADF in all branches that can use this ADF
      foreach (var subtree in symbolicExpressionTree.Root.Subtrees) {
        var matchingInvokeSymbol = (from symb in subtree.Grammar.Symbols.OfType<InvokeFunction>()
                                    where symb.FunctionName == selectedDefunBranch.FunctionName
                                    select symb).SingleOrDefault();
        if (matchingInvokeSymbol != null) {
          subtree.Grammar.SetSubtreeCount(matchingInvokeSymbol, selectedDefunBranch.NumberOfArguments, selectedDefunBranch.NumberOfArguments);
          foreach (var symb in subtree.Grammar.Symbols) {
            if (symb is StartSymbol || symb is ProgramRootSymbol) continue;
            if (subtree.Grammar.IsAllowedChildSymbol(matchingInvokeSymbol, symb, selectedArgumentSymbol.ArgumentIndex))
              subtree.Grammar.AddAllowedChildSymbol(matchingInvokeSymbol, symb, newArgumentIndex);
          }
        }
      }
      return true;
    }

    private static void DeletionByRandomRegeneration(IRandom random, ISymbolicExpressionTree symbolicExpressionTree, DefunTreeNode selectedDefunBranch) {
      // find first invocation and replace it with a randomly generated tree
      // can't find all invocations in one step because once we replaced a top level invocation
      // the invocations below it are removed already
      var invocationCutPoint = (from node in symbolicExpressionTree.IterateNodesPrefix()
                                from subtree in node.Subtrees.OfType<InvokeFunctionTreeNode>()
                                where subtree.Symbol.FunctionName == selectedDefunBranch.FunctionName
                                select new CutPoint(node, subtree)).FirstOrDefault();
      while (invocationCutPoint != null) {
        // deletion by random regeneration
        ISymbolicExpressionTreeNode replacementTree = null;
        var allowedSymbolsList = invocationCutPoint.Parent.Grammar.GetAllowedChildSymbols(invocationCutPoint.Parent.Symbol, invocationCutPoint.ChildIndex).ToList();
        var weights = allowedSymbolsList.Select(s => s.InitialFrequency);

#pragma warning disable 612, 618
        var selectedSymbol = allowedSymbolsList.SelectRandom(weights, random);
#pragma warning restore 612, 618


        int minPossibleLength = invocationCutPoint.Parent.Grammar.GetMinimumExpressionLength(selectedSymbol);
        int maxLength = Math.Max(minPossibleLength, invocationCutPoint.Child.GetLength());
        int minPossibleDepth = invocationCutPoint.Parent.Grammar.GetMinimumExpressionDepth(selectedSymbol);
        int maxDepth = Math.Max(minPossibleDepth, invocationCutPoint.Child.GetDepth());
        replacementTree = selectedSymbol.CreateTreeNode();
        if (replacementTree.HasLocalParameters)
          replacementTree.ResetLocalParameters(random);
        invocationCutPoint.Parent.RemoveSubtree(invocationCutPoint.ChildIndex);
        invocationCutPoint.Parent.InsertSubtree(invocationCutPoint.ChildIndex, replacementTree);

        ProbabilisticTreeCreator.PTC2(random, replacementTree, maxLength, maxDepth);

        invocationCutPoint = (from node in symbolicExpressionTree.IterateNodesPrefix()
                              from subtree in node.Subtrees.OfType<InvokeFunctionTreeNode>()
                              where subtree.Symbol.FunctionName == selectedDefunBranch.FunctionName
                              select new CutPoint(node, subtree)).FirstOrDefault();
      }
    }

    private void ComboBoxSelectedIndexChanged(object sender, EventArgs e) {
      string freeVariable = (string)comboBox.SelectedItem;
      IEnumerable<string> fixedVariables = comboBox.Items.OfType<string>()
        .Except(new string[] { freeVariable });

      variableNodes.Clear();
      clonedTree = (ISymbolicExpressionTree)Content.Model.SymbolicExpressionTree.Clone();

      foreach (var varNode in clonedTree.IterateNodesPrefix().OfType<VariableTreeNode>()) {
        if (fixedVariables.Contains(varNode.VariableName)) {
          if (!variableNodes.ContainsKey(varNode.VariableName))
            variableNodes.Add(varNode.VariableName, new List<ISymbolicExpressionTreeNode>());

          int childIndex = varNode.Parent.IndexOfSubtree(varNode);
          var replacementNode = MakeConstantTreeNode(medianValues[varNode.VariableName]);
          var parent = varNode.Parent;
          parent.RemoveSubtree(childIndex);
          parent.InsertSubtree(childIndex, MakeProduct(replacementNode, varNode.Weight));
          variableNodes[varNode.VariableName].Add(replacementNode);
        }
      }

      CreateSliders(fixedVariables);
      UpdateScatterPlot();
      UpdateResponseSeries();
    }

    public Tuple<IEnumerable<bool>, IEnumerable<double>, double, string, List<PythonStatementSemantic>> EvaluateAndTraceProgram(string program, string input, string output, IEnumerable<int> indices, string header, ISymbolicExpressionTree tree, double timeout = 1) {
      string traceProgram = traceCodeWithVariables
                          + program;
      traceProgram += traceCodeWithVariables == String.Empty
                    ? String.Empty
                    : traceTableReduceEntries;

      EvaluationScript es = pythonProcessParameter.ActualValue.CreateEvaluationScript(traceProgram, input, output, timeout);
      es.Variables.Add("traceTable");

      JObject json = pythonProcessParameter.ActualValue.SendAndEvaluateProgram(es);
      var baseResult = pythonProcessParameter.ActualValue.GetVariablesFromJson(json, indices.Count());

      if (json["traceTable"] == null) {
        return new Tuple<IEnumerable<bool>, IEnumerable<double>, double, string, List<PythonStatementSemantic>>(baseResult.Item1, baseResult.Item2, baseResult.Item3, baseResult.Item4, new List<PythonStatementSemantic>());
      }

      var traceTable = JsonConvert.DeserializeObject<IDictionary<int, IDictionary<string, IList>>>(json["traceTable"].ToString());
      IList<int> traceChanges = traceTable.Keys.OrderBy(x => x).ToList();

      List<PythonStatementSemantic> semantics = new List<PythonStatementSemantic>();
      ISymbolicExpressionTreeNode root = tree.Root;

      var statementProductions = ((GroupSymbol)root.Grammar.GetSymbol("Rule: <code>")).Symbols;
      var statementProductionNames = statementProductions.Select(x => x.Name);

      IList<int> lineTraces = traceTable.Keys.OrderBy(x => x).ToList();

      // add one, because the values are set after the statement is executed
      // add two, for inval and outval
      int curline = traceCode.Count(c => c == '\n') + header.Count(c => c == '\n') + 1 + 2;
      var symbolToLineDict = FindStatementSymbolsInTree(root, statementProductionNames, ref curline);
      var symbolLines = symbolToLineDict.Values.OrderBy(x => x).ToList();

      var prefixTreeNodes = tree.IterateNodesPrefix().ToList();

      foreach (var symbolLine in symbolToLineDict) {
        Dictionary<string, IList> before = new Dictionary<string, IList>();
        var linesBefore = lineTraces.Where(x => x <= symbolLine.Value).OrderByDescending(x => x);
        foreach (var l in linesBefore) {
          foreach (var change in traceTable[l]) {
            if (!before.ContainsKey(change.Key)) {
              before.Add(change.Key, change.Value);
            }
          }
        }

        int after = -1;
        int pos = traceChanges.IndexOf(linesBefore.Max());
        if (pos + 1 < traceChanges.Count // has to be in the array
                                         // there cannot be another line which comes after the current one, but before the trace change
                                         // otherwise the current line did not change anything
          && !symbolLines.Any(x => x > symbolLine.Value && x < traceChanges[pos + 1])) {
          after = traceChanges[pos + 1];
        }

        if (after >= 0) {
          semantics.Add(new PythonStatementSemantic() {
            TreeNodePrefixPos = prefixTreeNodes.IndexOf(symbolLine.Key),
            Before = before,
            After = traceTable[after],
          });
        } else {
          semantics.Add(new PythonStatementSemantic() {
            TreeNodePrefixPos = prefixTreeNodes.IndexOf(symbolLine.Key),
            Before = before,
            After = new Dictionary<string, IList>(),
          });
        }
      }

      return new Tuple<IEnumerable<bool>, IEnumerable<double>, double, string, List<PythonStatementSemantic>>(baseResult.Item1, baseResult.Item2, baseResult.Item3, baseResult.Item4, semantics);
    }