/// <summary>
/// find a optimal stump in sub dataset
/// </summary>
/// <param name="sortdata">sorted X[][dim]</param>
/// <param name="flag">flag of the sub dataset</param>
/// <param name="datasetFlags">flags of the whole dataset</param>
/// <param name="weight">current weight</param>
/// <returns>the stump of min Pm</returns>
Stump OptimalOneNode(SortedData sortdata, int flag, int[] datasetFlags, double[] weight)
{
int N = sortdata.N, MaxDim = sortdata.MaxDim;
List <Stump> stumpArray = new List <Stump>(MaxDim);
double[] sortedWeight = new double[sortdata.N];
object _lock = new object();
for (int dim = 1; dim <= MaxDim; dim++)
//Parallel.For(1, MaxDim + 1, dim =>
{
SortedNode[] sortedDim = sortdata[dim];
for (int n = 0; n < N; n++)
{
sortedWeight[n] = weight[sortedDim[n].N];
}
Stump stump = OptimalOneDim(sortedDim, flag, datasetFlags, sortedWeight, N, dim);
stumpArray.Add(stump);
}//);
stumpArray.Sort();
Stump beststump = null;
do
{
beststump = stumpArray[0];
stumpArray.RemoveAt(0);
} while (beststump == null && stumpArray.Count != 0);
return(beststump);
}
public TrainData CreateTrainData(Problem prob)
{
SortedData data = new SortedData();
data.GenTrainData(prob);
if (data.IsSparse == true)
{
string mesg = /*this.GetType().ToString()+*/ "StumpLearner do not support sparse data!";
throw new Exception(mesg);
}
return(data);
}
public TrainData CreateTrainData(Problem prob)
{
SortedData data = new SortedData();
data.GenTrainData(prob);
if (data.IsSparse == true)
{
string mesg = "TreeLearner do not support sparse data!";
throw new Exception(mesg);
}
return(data);
}
public double Train(TrainData data, double[] weight)
{
SortedData sortdata = data as SortedData;
int N = sortdata.N, MaxDim = sortdata.MaxDim;
List <Stump> stumpArray = new List <Stump>(MaxDim);
double[] sortedWeight = new double[sortdata.N];
for (int dim = 1; dim <= MaxDim; dim++)
{
SortedNode[] sortedDim = sortdata[dim];
//sort the weight as sortedDim
for (int n = 0; n < N; n++)
{
sortedWeight[n] = weight[sortedDim[n].N];
}
//find the best Stump in a dim.
Stump stump = OptimalOneDim(sortedDim, sortedWeight, N, dim);
stumpArray.Add(stump);
}
stumpArray.Sort();
_stump = stumpArray[0];
return(stumpArray[0].Pm);
}
// private Stump OptimalOneDim2(SortedNode[] sortedDim, int flag, int[] datasetFlags, double[] sortedWeight, int N, int dim)
// {
// //integral of (yn*wn) for speed improvement
// List<double> integralPos = new List<double>(N);
// List<double> integralNeg = new List<double>(N);
// List<double> valueCollection = new List<double>(N);
// for (int n = 0; n < N; )
// {
// if (datasetFlags[sortedDim[n].N] != flag)
// {
// n++;
// continue;
// }
//
// int offset = 0;
// while (n + offset < N && sortedDim[n].Value == sortedDim[n + offset].Value)
// {
// if (offset == 0)
// {
// integralPos.Add(0);
// integralNeg.Add(0);
// }
// int nx = n + offset;
// if (datasetFlags[sortedDim[nx].N] == flag)
// {
// if (sortedDim[n + offset].Y > 0)
// integralPos[integralPos.Count - 1] += sortedWeight[nx];
// else
// integralNeg[integralNeg.Count - 1] += sortedWeight[nx];
// }
// offset++;
// }
// valueCollection.Add(sortedDim[n].Value);
// n += offset;
// }
// for (int v = 1; v < integralNeg.Count; v++)
// {
// integralPos[v] += integralPos[v - 1];
// integralNeg[v] += integralNeg[v - 1];
// }
//
// // calculate error rates of (Count-1) split
// double[] errorPos = new double[integralPos.Count - 1];
// double[] errorNeg = new double[integralNeg.Count - 1];
// for (int v = 0; v < integralNeg.Count - 1; v++)
// {
// errorPos[v] = integralPos[v] + integralNeg[integralNeg.Count - 1] - integralNeg[v];
// errorNeg[v] = integralNeg[v] + integralPos[integralPos.Count - 1] - integralPos[v];
// }
//
// //find the min error rate as Pm and return the best stump of this dim
// int minPosIndex = 0, minNegIndex = 0;
// double errorPosMin = 1, errorNegMin = 1;
// for (int v = 1; v < errorPos.Length; v++)
// {
// if (errorPosMin >= errorPos[v])
// {
// minPosIndex = v;
// errorPosMin = errorPos[v];
// }
// if (errorNegMin >= errorNeg[v])
// {
// minNegIndex = v;
// errorNegMin = errorNeg[v];
// }
// }
//
// double sign = 1, threshold = 0, Pm = 0.49, Pl = 0.49, Pr = 0.49;
// if (errorNeg.Length < 1 || errorPos.Length < 1)
// {
// sign = -1;
// threshold = valueCollection[0];
// Pm = 1;
// return null;
// }
// else if (errorNegMin > errorPosMin)
// {
// sign = 1;
// threshold = 0.5 * (valueCollection[minPosIndex] + valueCollection[minPosIndex + 1]);
// Pm = errorPosMin;
// Pl = integralPos[minPosIndex];
// Pr = integralNeg[integralNeg.Count - 1] - integralNeg[minPosIndex];
// }
// else
// {
// threshold = 0.5 * (valueCollection[minNegIndex] + valueCollection[minNegIndex + 1]);
// sign = -1;
// Pm = errorNegMin;
// Pl = integralNeg[minNegIndex];
// Pr = integralPos[integralPos.Count - 1] - integralPos[minNegIndex];
// }
// return new Stump(dim, threshold, sign, Pm, Pl, Pr);
// }
/// <summary>
/// Cut the sub dataset of treeNode into 2 branches.
/// each branch sign with leftFlag and rightFlag.
/// </summary>
/// <param name="treeNode">the treeNode to cut</param>
/// <param name="sortdata">sorted X[][dim]</param>
/// <param name="leftFlag">flag of the left branch</param>
/// <param name="rightFlag">flag of the right branch</param>
/// <param name="datasetFlag">flags of the whole dataset</param>
/// <returns></returns>
private void CutDataSet(TreeNode treeNode, SortedData sortdata, int leftFlag, int rightFlag, ref int[] datasetFlag)
{
int N = sortdata.N;
SortedNode[] sortedDim = sortdata[treeNode.InnerStump.Dim];
double Thr = treeNode.InnerStump.Thr;
for (int n = 0; n < N; n++)
{
//SortedNode node = sortedDim[n];
if (datasetFlag[sortedDim[n].N] == treeNode.Flag)
{
if (sortedDim[n].Value > Thr)
{
datasetFlag[sortedDim[n].N] = rightFlag;
}
else
{
datasetFlag[sortedDim[n].N] = leftFlag;
}
}
}
}
public double Train(TrainData data, double[] weight)
{
SortedData sortdata = data as SortedData;
int N = sortdata.N, MaxDim = sortdata.MaxDim;
int[] datasetFlags = new int[sortdata.N];
int flag = 0;
Stump stump = OptimalOneNode(sortdata, flag, datasetFlags, weight);
if (stump == null)
{
throw new Exception(Messege.CouldNotClassify);
}
TreeNode treeNode = new TreeNode();
treeNode.InnerStump = stump;
treeNode.Parent = null;
treeNode.Flag = flag;
treeNode.Delta = 0.5 - treeNode.InnerStump.Pm;
List <TreeNode> priorityQueue = new List <TreeNode>();
priorityQueue.Add(treeNode);
double Pm = stump.Pm;
for (int splitIndex = 0; splitIndex < _maxSplit; splitIndex++)
{
do
{
treeNode = priorityQueue[0];
priorityQueue.RemoveAt(0);
} while (treeNode == null && priorityQueue.Count != 0);
if (treeNode == null)
{
break;
}
if (treeNode.Parent == null)
{
_treeRoot = treeNode;
}
else
{
if (treeNode.Flag % 2 != 0)
{
treeNode.Parent.Left = treeNode;
}
else
{
treeNode.Parent.Right = treeNode;
}
Pm = Pm - treeNode.Delta;
}
int leftFlag = ++flag;
int rightFlag = ++flag;
CutDataSet(treeNode, sortdata, leftFlag, rightFlag, ref datasetFlags);
TreeNode leftNode = null, rightNode = null;
if (treeNode.InnerStump.Pl > double.Epsilon)
{
stump = OptimalOneNode(sortdata, leftFlag, datasetFlags, weight);
if (stump != null)
{
leftNode = new TreeNode();
leftNode.InnerStump = stump;
leftNode.Parent = treeNode;
leftNode.Flag = leftFlag;
leftNode.Delta = treeNode.InnerStump.Pl - stump.Pm;
}
}
if (treeNode.InnerStump.Pr > double.Epsilon)
{
stump = OptimalOneNode(sortdata, rightFlag, datasetFlags, weight);
if (stump != null)
{
rightNode = new TreeNode();
rightNode.InnerStump = stump;
rightNode.Parent = treeNode;
rightNode.Flag = rightFlag;
rightNode.Delta = treeNode.InnerStump.Pr - stump.Pm;
}
}
priorityQueue.Add(leftNode);
priorityQueue.Add(rightNode);
priorityQueue.Sort();
}
return(Pm);
}