/**
* Splits a node into two based on the midpoint value of the dimension in which the node's
* rectangle is widest. If after splitting one side is empty then it is slided towards the
* non-empty side until there is at least one point on the empty side. The two nodes created after
* the whole splitting are correctly initialised. And, node.left and node.right are set
* appropriately.
*
* @param node The node to split.
* @param numNodesCreated The number of nodes that so far have been created for the tree, so that
* the newly created nodes are assigned correct/meaningful node numbers/ids.
* @param nodeRanges The attributes' range for the points inside the node that is to be split.
* @param universe The attributes' range for the whole point-space.
* @throws Exception If there is some problem in splitting the given node.
*/
public void splitNode(
KDTreeNode node, int numNodesCreated, double[][] nodeRanges, double[][] universe)
throws Exception {
correctlyInitialized();
if (node.m_NodesRectBounds == null) {
node.m_NodesRectBounds = new double[2][node.m_NodeRanges.length];
for (int i = 0; i < node.m_NodeRanges.length; i++) {
node.m_NodesRectBounds[MIN][i] = node.m_NodeRanges[i][MIN];
node.m_NodesRectBounds[MAX][i] = node.m_NodeRanges[i][MAX];
}
}
// finding widest side of the hyper rectangle
double maxRectWidth = Double.NEGATIVE_INFINITY, maxPtWidth = Double.NEGATIVE_INFINITY, tempval;
int splitDim = -1, classIdx = m_Instances.classIndex();
for (int i = 0; i < node.m_NodesRectBounds[0].length; i++) {
if (i == classIdx) continue;
tempval = node.m_NodesRectBounds[MAX][i] - node.m_NodesRectBounds[MIN][i];
if (m_NormalizeNodeWidth) {
tempval = tempval / universe[i][WIDTH];
}
if (tempval > maxRectWidth && node.m_NodeRanges[i][WIDTH] > 0.0) maxRectWidth = tempval;
}
for (int i = 0; i < node.m_NodesRectBounds[0].length; i++) {
if (i == classIdx) continue;
tempval = node.m_NodesRectBounds[MAX][i] - node.m_NodesRectBounds[MIN][i];
if (m_NormalizeNodeWidth) {
tempval = tempval / universe[i][WIDTH];
}
if (tempval >= maxRectWidth * (1 - ERR) && node.m_NodeRanges[i][WIDTH] > 0.0) {
if (node.m_NodeRanges[i][WIDTH] > maxPtWidth) {
maxPtWidth = node.m_NodeRanges[i][WIDTH];
if (m_NormalizeNodeWidth) maxPtWidth = maxPtWidth / universe[i][WIDTH];
splitDim = i;
}
}
}
double splitVal =
node.m_NodesRectBounds[MIN][splitDim]
+ (node.m_NodesRectBounds[MAX][splitDim] - node.m_NodesRectBounds[MIN][splitDim]) * 0.5;
// might want to try to slide it further to contain more than one point on
// the
// side that is resulting empty
if (splitVal < node.m_NodeRanges[splitDim][MIN]) splitVal = node.m_NodeRanges[splitDim][MIN];
else if (splitVal >= node.m_NodeRanges[splitDim][MAX])
splitVal = node.m_NodeRanges[splitDim][MAX] - node.m_NodeRanges[splitDim][WIDTH] * 0.001;
int rightStart = rearrangePoints(m_InstList, node.m_Start, node.m_End, splitDim, splitVal);
if (rightStart == node.m_Start || rightStart > node.m_End) {
if (rightStart == node.m_Start)
throw new Exception(
"Left child is empty in node "
+ node.m_NodeNumber
+ ". Not possible with "
+ "SlidingMidPointofWidestSide splitting method. Please "
+ "check code.");
else
throw new Exception(
"Right child is empty in node "
+ node.m_NodeNumber
+ ". Not possible with "
+ "SlidingMidPointofWidestSide splitting method. Please "
+ "check code.");
}
node.m_SplitDim = splitDim;
node.m_SplitValue = splitVal;
double[][] widths = new double[2][node.m_NodesRectBounds[0].length];
System.arraycopy(
node.m_NodesRectBounds[MIN], 0, widths[MIN], 0, node.m_NodesRectBounds[MIN].length);
System.arraycopy(
node.m_NodesRectBounds[MAX], 0, widths[MAX], 0, node.m_NodesRectBounds[MAX].length);
widths[MAX][splitDim] = splitVal;
node.m_Left =
new KDTreeNode(
numNodesCreated + 1,
node.m_Start,
rightStart - 1,
m_EuclideanDistance.initializeRanges(m_InstList, node.m_Start, rightStart - 1),
widths);
widths = new double[2][node.m_NodesRectBounds[0].length];
System.arraycopy(
node.m_NodesRectBounds[MIN], 0, widths[MIN], 0, node.m_NodesRectBounds[MIN].length);
System.arraycopy(
node.m_NodesRectBounds[MAX], 0, widths[MAX], 0, node.m_NodesRectBounds[MAX].length);
widths[MIN][splitDim] = splitVal;
node.m_Right =
new KDTreeNode(
numNodesCreated + 2,
rightStart,
node.m_End,
m_EuclideanDistance.initializeRanges(m_InstList, rightStart, node.m_End),
widths);
}
