public void ReplaceRandomBranch(IRandom random, ISymbolicExpressionTree symbolicExpressionTree, int maxTreeLength, int maxTreeDepth)
{
var allowedSymbols = new List <ISymbol>();
ISymbolicExpressionTreeNode parent;
int childIndex;
int maxLength;
int maxDepth;
// repeat until a fitting parent and child are found (MAX_TRIES times)
int tries = 0;
do
{
#pragma warning disable 612, 618
parent = symbolicExpressionTree.Root.IterateNodesPrefix().Skip(1).Where(n => n.SubtreeCount > 0).SelectRandom(random);
#pragma warning restore 612, 618
childIndex = random.Next(parent.SubtreeCount);
var child = parent.GetSubtree(childIndex);
maxLength = maxTreeLength - symbolicExpressionTree.Length + child.GetLength();
maxDepth = maxTreeDepth - symbolicExpressionTree.Root.GetBranchLevel(child);
allowedSymbols.Clear();
foreach (var symbol in parent.Grammar.GetAllowedChildSymbols(parent.Symbol, childIndex))
{
// check basic properties that the new symbol must have
if ((symbol.Name != child.Symbol.Name || symbol.MinimumArity > 0) &&
symbol.InitialFrequency > 0 &&
parent.Grammar.GetMinimumExpressionDepth(symbol) <= maxDepth &&
parent.Grammar.GetMinimumExpressionLength(symbol) <= maxLength)
{
allowedSymbols.Add(symbol);
}
}
tries++;
} while (tries < MAX_TRIES && allowedSymbols.Count == 0);
if (tries < MAX_TRIES)
{
var weights = allowedSymbols.Select(s => s.InitialFrequency).ToList();
#pragma warning disable 612, 618
var seedSymbol = allowedSymbols.SelectRandom(weights, random);
#pragma warning restore 612, 618
// replace the old node with the new node
var seedNode = seedSymbol.CreateTreeNode();
if (seedNode.HasLocalParameters)
{
seedNode.ResetLocalParameters(random);
}
CutPointSymbolParameter.ActualValue = (ISymbol)parent.Symbol.Clone();
RemovedBranchParameter.ActualValue = new SymbolicExpressionTree((ISymbolicExpressionTreeNode)parent.GetSubtree(childIndex).Clone());
parent.RemoveSubtree(childIndex);
parent.InsertSubtree(childIndex, seedNode);
ProbabilisticTreeCreator.PTC2(random, seedNode, maxLength, maxDepth);
AddedBranchParameter.ActualValue = new SymbolicExpressionTree((ISymbolicExpressionTreeNode)parent.GetSubtree(childIndex).Clone());
}
}
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();
}
}