/// <summary>
/// Method that implements the subtree mutation or "headless chicken" crossover described in Section 2.4 of "A Field Guide to Genetic Programming"
/// </summary>
/// <param name="iMaxProgramDepth">The max depth of the tree after the mutation</param>
public void Mutate(int iMaxProgramDepth, string method, object tag = null)
{
if (method == MUTATION_SUBTREE || method == MUTATION_SUBTREE_KINNEAR)
{
TGPNode node = FindRandomNode();
if (method == MUTATION_SUBTREE)
{
int node_depth = mRootNode.FindDepth2Node(node);
node.RemoveAllChildren();
node.Primitive = FindRandomPrimitive();
if (!node.Primitive.IsTerminal)
{
int max_depth = iMaxProgramDepth - node_depth;
CreateWithDepth(node, max_depth, INITIALIZATION_METHOD_GROW);
}
}
else
{
int subtree_depth = mRootNode.FindDepth2Node(node);
int current_depth = mDepth - subtree_depth;
int max_depth = (int)(mDepth * 1.15) - current_depth;
node.RemoveAllChildren();
node.Primitive = FindRandomPrimitive();
if (!node.Primitive.IsTerminal)
{
CreateWithDepth(node, max_depth, INITIALIZATION_METHOD_GROW);
}
}
}
else if (method == MUTATION_HOIST)
{
TGPNode node = FindRandomNode();
if (node != mRootNode)
{
node.Parent = null;
mRootNode = node;
}
}
else if (method == MUTATION_SHRINK)
{
TGPNode node = FindRandomNode();
node.RemoveAllChildren();
node.Primitive = FindRandomTerminal();
}
CalcDepth();
CalcLength();
}
public void Swap(TGPNode point2)
{
TGPNode parent1 = this.mParent;
TGPNode parent2 = point2.mParent;
if (parent1 == null || parent2 == null)
{
TGPPrimitive content1 = this.mData;
TGPPrimitive content2 = point2.mData;
this.mData = content2;
point2.mData = content1;
List <TGPNode> children1 = this.mChildNodes.ToList();
List <TGPNode> children2 = point2.mChildNodes.ToList();
this.RemoveAllChildren();
point2.RemoveAllChildren();
for (int i = 0; i < children1.Count; ++i)
{
point2.mChildNodes.Add(children1[i]);
children1[i].Parent = point2;
}
for (int i = 0; i < children2.Count; ++i)
{
this.mChildNodes.Add(children2[i]);
children2[i].Parent = this;
}
}
else
{
int child_index1 = parent1.IndexOfChild(this);
int child_index2 = parent2.IndexOfChild(point2);
parent1.ReplaceChildAt(child_index1, point2);
parent2.ReplaceChildAt(child_index2, this);
}
}