public Queue<List<Double>> findNeighbors(int k, List<Double> point) {
Queue<List<Double>> pointsN = getPointsQueue(point);
Queue<BallNode> ballsQueueQ = getBallsQueue(point);
ballsQueueQ.add(root);
while (!ballsQueueQ.isEmpty()) {
BallNode ballS = ballsQueueQ.poll();
if (pointsN.size() >= k) {
if (ballS.distanceTo(point) > distance(pointsN.peek(), point)) {
return pointsN;
}
}
if (ballS.isLeaf()) {
for (List<Double> p : ballS.points.getData()) {
pointsN.add(p);
}
while (pointsN.size() > k) {
pointsN.poll();
}
} else {
ballsQueueQ.add(ballS.left);
ballsQueueQ.add(ballS.right);
}
}
return pointsN;
}
/**
* Builds a ball tree middle out.
*
* @return The root node of the tree.
* @throws Exception If there is problem building the tree.
*/
public BallNode buildTree() throws Exception {
m_NumNodes = m_MaxDepth = m_NumLeaves = 0;
if (rootRadius == -1) {
rootRadius =
BallNode.calcRadius(
m_InstList,
m_Instances,
BallNode.calcCentroidPivot(m_InstList, m_Instances),
m_DistanceFunction);
}
BallNode root = buildTreeMiddleOut(0, m_Instances.numInstances() - 1);
return root;
}
/**
* Applies the middle out build procedure to the leaves of the tree. The leaf nodes should be the
* ones that were created by createAnchorsHierarchy(). The process continues recursively for the
* leaves created for each leaf of the given tree until for some leaf node <= m_MaxInstancesInLeaf
* instances remain in the leaf.
*
* @param node The root of the tree.
* @throws Exception If there is some problem in building the tree leaves.
*/
protected void buildLeavesMiddleOut(BallNode node) throws Exception {
if (node.m_Left != null && node.m_Right != null) { // if an internal node
buildLeavesMiddleOut(node.m_Left);
buildLeavesMiddleOut(node.m_Right);
} else if (node.m_Left != null || node.m_Right != null) {
throw new Exception("Invalid leaf assignment. Please check code");
} else { // if node is a leaf
BallNode n2 = buildTreeMiddleOut(node.m_Start, node.m_End);
if (n2.m_Left != null && n2.m_Right != null) {
node.m_Left = n2.m_Left;
node.m_Right = n2.m_Right;
buildLeavesMiddleOut(node);
// the stopping condition in buildTreeMiddleOut will stop the recursion,
// where it won't split a node at all, and we won't recurse here.
} else if (n2.m_Left != null || n2.m_Right != null)
throw new Exception("Invalid leaf assignment. Please check code");
}
}
/**
* Makes BallTreeNodes out of TempNodes.
*
* @param node The root TempNode
* @param startidx The start of the portion of master index array the TempNodes are made from.
* @param endidx The end of the portion of master index array the TempNodes are made from.
* @param depth The depth in the tree where this root TempNode is made (needed when leaves of a
* tree deeper down are built middle out).
* @return The root BallTreeNode.
*/
protected BallNode makeBallTreeNodes(TempNode node, int startidx, int endidx, int depth) {
BallNode ball = null;
if (node.left != null && node.right != null) { // make an internal node
ball = new BallNode(startidx, endidx, m_NumNodes, node.anchor, node.radius);
m_NumNodes += 1;
ball.m_Left =
makeBallTreeNodes(
node.left, startidx, startidx + node.left.points.length() - 1, depth + 1);
ball.m_Right =
makeBallTreeNodes(node.right, startidx + node.left.points.length(), endidx, depth + 1);
m_MaxDepth++;
} else { // make a leaf node
ball = new BallNode(startidx, endidx, m_NumNodes, node.anchor, node.radius);
m_NumNodes += 1;
m_NumLeaves += 1;
}
return ball;
}
/**
* Builds a ball tree middle out from the portion of the master index array given by supplied
* start and end index.
*
* @param startIdx The start of the portion in master index array.
* @param endIdx the end of the portion in master index array.
* @return The root node of the built tree.
* @throws Exception If there is some problem building the tree.
*/
protected BallNode buildTreeMiddleOut(int startIdx, int endIdx) throws Exception {
Instance pivot;
double radius;
Vector<TempNode> anchors;
int numInsts = endIdx - startIdx + 1;
int numAnchors = (int) Math.round(Math.sqrt(numInsts));
// create anchor's hierarchy
if (numAnchors > 1) {
pivot = BallNode.calcCentroidPivot(startIdx, endIdx, m_InstList, m_Instances);
radius =
BallNode.calcRadius(startIdx, endIdx, m_InstList, m_Instances, pivot, m_DistanceFunction);
if (numInsts <= m_MaxInstancesInLeaf
|| (rootRadius == 0
? true
: radius / rootRadius
< m_MaxRelLeafRadius)) { // just make a leaf don't make anchors hierarchy
BallNode node = new BallNode(startIdx, endIdx, m_NumNodes, pivot, radius);
return node;
}
anchors = new Vector<TempNode>(numAnchors);
createAnchorsHierarchy(anchors, numAnchors, startIdx, endIdx);
BallNode node = mergeNodes(anchors, startIdx, endIdx);
buildLeavesMiddleOut(node);
return node;
} // end anchors hierarchy
else {
BallNode node =
new BallNode(
startIdx,
endIdx,
m_NumNodes,
(pivot = BallNode.calcCentroidPivot(startIdx, endIdx, m_InstList, m_Instances)),
BallNode.calcRadius(
startIdx, endIdx, m_InstList, m_Instances, pivot, m_DistanceFunction));
return node;
}
}
/**
* Returns an anchor point which is furthest from the mean point for a given set of points
* (instances) (The anchor instance is chosen from the given set of points).
*
* @param startIdx The start index of the points for which anchor point is required.
* @param endIdx The end index of the points for which anchor point is required.
* @return The furthest point/instance from the mean of given set of points.
*/
protected TempNode getFurthestFromMeanAnchor(int startIdx, int endIdx) {
TempNode anchor = new TempNode();
Instance centroid = BallNode.calcCentroidPivot(startIdx, endIdx, m_InstList, m_Instances);
Instance temp;
double tmpr;
anchor.radius = Double.NEGATIVE_INFINITY;
for (int i = startIdx; i <= endIdx; i++) {
temp = m_Instances.instance(m_InstList[i]);
tmpr = m_DistanceFunction.distance(centroid, temp);
if (tmpr > anchor.radius) {
anchor.idx = m_InstList[i];
anchor.anchor = temp;
anchor.radius = tmpr;
}
}
setPoints(anchor, startIdx, endIdx, m_InstList);
return anchor;
}
public BallTree(Matrix points, int k) {
root = BallNode.buildBallNode(points, k);
}
