// insert a new parition split (find insertion point and start at first element of the queue)
// elements are removed from the queue at the last position
// O(n), splits could be organized as a heap to improve runtime (see alglib tsort)
private void InsertSortedQueue(PartitionSplits split)
{
// find insertion position
int i = 0;
while (i < queue.Count && queue[i].SplittingImprovement < split.SplittingImprovement)
{
i++;
}
queue.Insert(i, split);
}
// calculates the optimal split for the partition [startIdx .. endIdx] (inclusive)
// which is represented by the leaf node with the specified nodeIdx
private void EnqueuePartitionSplit(int nodeIdx, int startIdx, int endIdx)
{
double threshold, improvement;
string bestVariableName;
// only enqueue a new split if there are at least 2 rows left and a split is possible
if (startIdx < endIdx &&
FindBestVariableAndThreshold(startIdx, endIdx, out threshold, out bestVariableName, out improvement))
{
var split = new PartitionSplits()
{
ParentNodeIdx = nodeIdx,
StartIdx = startIdx,
EndIndex = endIdx,
SplittingThreshold = threshold,
SplittingVariable = bestVariableName
};
InsertSortedQueue(split);
}
}
// insert a new parition split (find insertion point and start at first element of the queue)
// elements are removed from the queue at the last position
// O(n), splits could be organized as a heap to improve runtime (see alglib tsort)
private void InsertSortedQueue(PartitionSplits split) {
// find insertion position
int i = 0;
while (i < queue.Count && queue[i].SplittingImprovement < split.SplittingImprovement) { i++; }
queue.Insert(i, split);
}
// calculates the optimal split for the partition [startIdx .. endIdx] (inclusive)
// which is represented by the leaf node with the specified nodeIdx
private void EnqueuePartitionSplit(int nodeIdx, int startIdx, int endIdx) {
double threshold, improvement;
string bestVariableName;
// only enqueue a new split if there are at least 2 rows left and a split is possible
if (startIdx < endIdx &&
FindBestVariableAndThreshold(startIdx, endIdx, out threshold, out bestVariableName, out improvement)) {
var split = new PartitionSplits() {
ParentNodeIdx = nodeIdx,
StartIdx = startIdx,
EndIndex = endIdx,
SplittingThreshold = threshold,
SplittingVariable = bestVariableName
};
InsertSortedQueue(split);
}
}