/// <summary>
/// Returns true if inner1 can feasibly be swapped into inner2's position.
/// </summary>
private bool VerifyPoints(GPInitializer initializer, GPNode inner1, GPNode inner2)
{
// first check to see if inner1 is swap-compatible with inner2
// on a type basis
if (!inner1.SwapCompatibleWith(initializer, inner2))
{
return(false);
}
// next check to see if inner1 can fit in inner2's spot
if (inner1.Depth + inner2.AtDepth() > MaxDepth)
{
return(false);
}
// checks done!
return(true);
}
/// <summary>
/// Returns true if inner1 can feasibly be swapped into inner2's position.
/// </summary>
public bool VerifyPoints(GPInitializer initializer, GPNode inner1, GPNode inner2)
{
// first check to see if inner1 is swap-compatible with inner2
// on a type basis
if (!inner1.SwapCompatibleWith(initializer, inner2))
{
return(false);
}
// next check to see if inner1 can fit in inner2's spot
if (inner1.Depth + inner2.AtDepth() > MaxDepth)
{
return(false);
}
// check for size
// NOTE: this is done twice, which is more costly than it should be. But
// on the other hand it allows us to toss a child without testing both times
// and it's simpler to have it all here in the verifyPoints code.
if (MaxSize != NO_SIZE_LIMIT)
{
// first easy check
var inner1Size = inner1.NumNodes(GPNode.NODESEARCH_ALL);
var inner2Size = inner2.NumNodes(GPNode.NODESEARCH_ALL);
if (inner1Size > inner2Size) // need to test further
{
// let's keep on going for the more complex test
var root2 = ((GPTree)(inner2.RootParent())).Child;
var root2Size = root2.NumNodes(GPNode.NODESEARCH_ALL);
if (root2Size - inner2Size + inner1Size > MaxSize) // take root2, remove inner2 and swap in inner1. Is it still small enough?
{
return(false);
}
}
}
// checks done!
return(true);
}
/**
* This method finds a node using the logic given in the langdon paper.
* @param nodeToSubtrees For Tree of Parent2 all precomputed stats about depth,subtrees etc
* @param sizeToNodes Quick lookup for LinkedList of size to Nodes
* @param parent1SelectedNode Node selected in parent1
* @param Tree2 Tree of parent2
* @param state Evolution State passed for getting access to Random Object of MersenneTwiser
* @param thread thread number
*/
protected GPNode FindFairSizeNode(ArrayList nodeToSubtrees,
Hashtable sizeToNodes,
GPNode parent1SelectedNode,
GPTree tree2,
IEvolutionState state,
int thread)
{
GPNode selectedNode = null;
// get the size of subtrees of parent1
int parent1SubTrees = parent1SelectedNode.NumNodes(GPNode.NODESEARCH_NONTERMINALS);
// the maximum length in mate we are looking for
int maxmatesublen = parent1SubTrees == 0 ? 0 : 2 * parent1SubTrees + 1;
// lets see if for all lengths we have trees corresponding
bool[] mateSizeAvailable = new bool[maxmatesublen + 1];
// initialize the array to false
for (int i = 0; i < maxmatesublen; i++)
{
mateSizeAvailable[i] = false;
}
// check for ones we have
for (int i = 0; i < nodeToSubtrees.Count; i++)
{
NodeInfo nodeInfo = (NodeInfo)nodeToSubtrees[i];
// get the length of trees
int subtree = nodeInfo.NumberOfSubTreesBeneath;
if (subtree <= maxmatesublen)
{
mateSizeAvailable[subtree] = true;
}
}
// choose matesublen so mean size change=0 if possible
int countOfPositives = 0;
int countOfNegatives = 0;
int sumOfPositives = 0;
int sumOfNegatives = 0;
int l;
for (l = 1; l < parent1SubTrees; l++)
{
if (mateSizeAvailable[l])
{
countOfNegatives++;
sumOfNegatives += parent1SubTrees - l;
}
}
for (l = parent1SubTrees + 1; l <= maxmatesublen; l++)
{
if (mateSizeAvailable[l])
{
countOfPositives++;
sumOfPositives += l - parent1SubTrees;
}
}
// if they are missing use the same
int mateSublengthSelected = 0;
if (sumOfPositives == 0 || sumOfNegatives == 0)
{
//if so then check if mate has the length and use that
if (mateSizeAvailable[parent1SubTrees])
{
mateSublengthSelected = parent1SubTrees;
}
//else we go with zero
}
else
{
// probability of same is dependent on do we find same sub trees
// else 0.0
double pzero = (mateSizeAvailable[parent1SubTrees]) ? 1.0 / parent1SubTrees : 0.0;
// positive probability
double ppositive = (1.0 - pzero) /
(countOfPositives +
((double)(countOfNegatives * sumOfPositives) / (sumOfNegatives)));
// negative probability
double pnegative = (1.0 - pzero) /
(countOfNegatives +
((double)(countOfPositives * sumOfNegatives) / (sumOfPositives)));
// total probability, just for making sure math is right ;-)
double total = countOfNegatives * pnegative + pzero + countOfPositives * ppositive;
// putting an assert for floating point calculations, similar to what langdon does
// assert(total<1.01&&total>.99);
// now create a Roulette Wheel
RouletteWheelSelector wheel = new RouletteWheelSelector(maxmatesublen);
// add probabilities to the wheel
// all below the length of parent node get pnegative
// all above get ppositive and one on node gets pzero
for (l = 1; l < parent1SubTrees; l++)
{
if (mateSizeAvailable[l])
{
wheel.Add(pnegative, l);
}
}
if (mateSizeAvailable[parent1SubTrees])
{
wheel.Add(pzero, parent1SubTrees);
}
for (l = parent1SubTrees + 1; l <= maxmatesublen; l++)
{
if (mateSizeAvailable[l])
{
wheel.Add(ppositive, l);
}
}
// spin the wheel
mateSublengthSelected = wheel.Roulette(state, thread);
}
// now we have length chosen, but there can be many nodes with that
//
LinkedList <NodeInfo> listOfNodes = (LinkedList <NodeInfo>)sizeToNodes[mateSublengthSelected];
if (listOfNodes == null)
{
state.Output.Fatal("In SizeFairCrossoverPipeline, nodes for tree length " + mateSublengthSelected + " is null, indicates some serious error");
}
// in size fair we choose the elements at random for given length
int chosenNode = 0;
// if using fair size get random from the list
if (!Homologous)
{
chosenNode = state.Random[thread].NextInt(listOfNodes.Count);
}
// if Homologous
else
{
if (listOfNodes.Count > 1)
{
GPInitializer initializer = ((GPInitializer)state.Initializer);
int currentMinDistance = int.MaxValue;
for (int i = 0; i < listOfNodes.Count; i++)
{
// get the GP node
GPNode selectedMateNode = listOfNodes.ElementAt(i).Node;
// now lets traverse selected and parent 1 to see divergence
GPNode currentMateNode = selectedMateNode;
GPNode currentParent1Node = parent1SelectedNode;
// found a match?
bool foundAMatchInAncestor = false;
int distance = 0;
while (currentMateNode.Parent != null &&
currentMateNode.Parent is GPNode &&
currentParent1Node.Parent != null &&
currentParent1Node.Parent is GPNode &&
!foundAMatchInAncestor)
{
GPNode parent1 = (GPNode)currentParent1Node.Parent;
GPNode parent2 = (GPNode)currentMateNode.Parent;
// if there is match between compatibility of Parents break
if (parent1.SwapCompatibleWith(initializer, parent2))
{
foundAMatchInAncestor = true;
break;
}
else
{
// need to go one level above of both
currentMateNode = parent2;
currentParent1Node = parent1;
//increment the distance
distance = distance + 1;
}
}
// find the one with least distance
if (distance < currentMinDistance)
{
currentMinDistance = distance;
chosenNode = i;
}
}
}
// else take the first node, no choice
}
NodeInfo nodeInfoSelected = listOfNodes.ElementAt(chosenNode);
selectedNode = nodeInfoSelected.Node;
return(selectedNode);
}