/// <summary>
/// Population Initialization method following the "PTC1" method described in "Sean Luke. Two fast tree-creation algorithms for genetic programming. IEEE Transactions in Evolutionary Computation, 4(3), 2000b."
/// </summary>
/// <param name="parent_node">The node for which the child nodes are generated in this method</param>
/// <param name="p">expected probability</param>
/// <param name="allowableDepth">The maximum tree depth</param>
private void PTC1(TGPNode parent_node, double p, int allowableDepth)
{
int child_count = parent_node.Arity;
for (int i = 0; i != child_count; i++)
{
TGPPrimitive data = null;
if (allowableDepth == 0)
{
data = FindRandomTerminal();
}
else if (DistributionModel.GetUniform() <= p)
{
data = mOperatorSet.FindRandomOperator();
}
else
{
data = FindRandomTerminal();
}
TGPNode child = parent_node.CreateChild(data);
if (!data.IsTerminal)
{
PTC1(child, p, allowableDepth - 1);
}
}
}
/// <summary>
/// Population Initialization Method described in "Kumar Chellapilla. Evolving computer programs without subtree crossover. IEEE Transactions on Evolutionary Computation, 1(3):209–216, September 1997."
/// </summary>
/// <param name="parent_node"></param>
/// <param name="s"></param>
/// <param name="?"></param>
private void RandomBranch(TGPNode parent_node, int s)
{
int child_count = parent_node.Arity;
for (int i = 0; i != child_count; i++)
{
TGPOperator non_terminal = FindRandomOperatorWithArityLessThan(s);
if (non_terminal == null)
{
TGPNode child = parent_node.CreateChild(FindRandomTerminal());
}
else
{
TGPNode child = parent_node.CreateChild(non_terminal);
int b_n = non_terminal.Arity;
int s_pi = (int)System.Math.Floor((double)s / b_n);
RandomBranch(child, s_pi);
}
}
}
/// <summary>
/// Method that creates a subtree of maximum depth
/// </summary>
/// <param name="pRoot">The root node of the subtree</param>
/// <param name="allowableDepth">The maximum depth</param>
/// <param name="method">The method used to build the subtree</param>
public void CreateWithDepth(TGPNode pRoot, int allowableDepth, string method)
{
int child_count = pRoot.Arity;
for (int i = 0; i != child_count; ++i)
{
TGPPrimitive primitive = FindRandomPrimitive(allowableDepth, method);
TGPNode child = pRoot.CreateChild(primitive);
if (!primitive.IsTerminal)
{
CreateWithDepth(child, allowableDepth - 1, method);
}
}
}
