public override NodeBaseType <T, S> SelectRandom(ref int numNodesConsidered)
{
float selectPercentage = 1F / numNodesConsidered;
// possibly pick myself
NodeBaseType <T, S> selected = null;
if (Randomizer.GetFloatFromZeroToOne() < selectPercentage)
{
selected = this;
}
// but also consider all of my children
foreach (var child in Children)
{
numNodesConsidered++;
var selectedFromChild = child.SelectRandom(ref numNodesConsidered);
if (selectedFromChild != null)
{
selected = selectedFromChild;
}
}
return(selected);
}
internal static void SwapSubtrees(
NodeBaseType <T, S> selectedNode1, NodeBaseType <T, S> selectedNode2,
NodeBaseType <T, S> replacementNode1, NodeBaseType <T, S> replacementNode2)
{
// find the child we're going to replace
var parent = (FunctionNode <T, S>)selectedNode1.Parent;
for (int i = 0; i < parent.Children.Count; i++)
{
if (parent.Children[i] == selectedNode1)
{
parent.Children[i] = replacementNode2;
replacementNode2.Parent = parent;
selectedNode1.Parent = null;
break;
}
}
// find the child we're going to replace
parent = (FunctionNode <T, S>)selectedNode2.Parent;
for (int i = 0; i < parent.Children.Count; i++)
{
if (parent.Children[i] == selectedNode2)
{
parent.Children[i] = replacementNode1;
replacementNode1.Parent = parent;
selectedNode2.Parent = null;
break;
}
}
}
internal void Mutate()
{
// pick any node but the root (since that would be a replacement of the entire tree, not a mutation)
NodeBaseType <T, S> randomNode = null;
do
{
randomNode = SelectRandomNode();
} while (randomNode == Root);
// build a random subtree
bool buildFullTrees = Randomizer.GetFloatFromZeroToOne() < 0.5F;
int depth = Randomizer.IntBetween(TreeMinDepth, TreeMaxDepth);
var newSubtree = AddRandomNode(null, depth, buildFullTrees);
// replace the randomly selected node with the new random one
var parent = (FunctionNode <T, S>)randomNode.Parent;
newSubtree.Parent = parent;
// find the link from the parent to the old child, and replace it
for (int i = 0; i < parent.Children.Count; i++)
{
if (parent.Children[i] == randomNode)
{
parent.Children[i] = newSubtree;
break;
}
}
}
public override NodeBaseType <T, S> Clone(NodeBaseType <T, S> parentNode)
{
var newNode = new TerminalFunctionNode <T, S>(functionMetadata, ownerCandidate);
newNode.Parent = parentNode;
return(newNode);
}
public override NodeBaseType <T, S> Clone(NodeBaseType <T, S> parentNode)
{
// clone the node
var newNode = new FunctionNode <T, S>(functionMetadata, ownerCandidate);
newNode.Parent = parentNode;
// clone the children
foreach (var child in Children)
{
newNode.Children.Add(child.Clone(newNode));
}
return(newNode);
}
internal NodeBaseType <T, S> AddRandomNode(NodeBaseType <T, S> parentNode, int levelsToCreate, bool buildFullTrees)
{
// we're either adding a terminal node (const or var), or a function node (which has children)
bool addingTerminal = false;
// if we're at the max depth, add a terminal node
if (levelsToCreate == 0)
{
addingTerminal = true;
}
else
if (levelsToCreate >= TreeMinDepth)
{
// make sure we're at least a certain depth
addingTerminal = false;
}
else
{
// we're somewhere between the min and max depth
if (buildFullTrees)
{
addingTerminal = false;
}
else
{
// pick a random type, either function or terminal
int numFuncs = primitiveSet.Functions.Count;
int numTerminalFuncs = primitiveSet.TerminalFunctions.Count;
int numVars = primitiveSet.VariableNames.Count;
int numConsts = primitiveSet.Constants.Count;
int random = Randomizer.IntLessThan(numFuncs + numTerminalFuncs + numVars + numConsts);
if (random < numFuncs)
{
addingTerminal = false;
}
else
{
addingTerminal = true;
}
}
}
// Now that we know whether to add a function or terminal node, go ahead and do it
if (addingTerminal)
{
var termNode = NewRandomTerminalNode();
termNode.Parent = parentNode;
return(termNode);
}
else
{
var funcNode = NewRandomFunctionNode();
funcNode.Parent = parentNode;
int numKids = funcNode.NumArguments;
for (int i = 0; i < numKids; i++)
{
// recursively create descendent nodes
funcNode.Children.Add(AddRandomNode(funcNode, levelsToCreate - 1, buildFullTrees));
}
return(funcNode);
}
}
