@Override
public boolean findNearest(double[] point, double maxDistance, NnData<PointData> result) {
boolean r =
searchNearest(
point, maxDistance < 0 ? Double.POSITIVE_INFINITY : Math.sqrt(maxDistance), result);
result.distance *= result.distance; // Callee expects squared distance
return r;
}
@Override
public void findNearest(
double[] target, double maxDistance, int numNeighbors, FastQueue<NnData<PointData>> results) {
PriorityQueue<HeapItem> heap =
search(
target,
maxDistance < 0 ? Double.POSITIVE_INFINITY : Math.sqrt(maxDistance),
numNeighbors);
while (!heap.isEmpty()) {
final HeapItem heapItem = heap.poll();
NnData<PointData> objects = new NnData<PointData>();
objects.data = itemData[heapItem.index];
objects.point = items[heapItem.index];
objects.distance = heapItem.dist * heapItem.dist; // squared distance is expected
results.add(objects);
}
results.reverse();
}
/**
* Equivalent to the above search method to find one nearest neighbor. It is faster as it does not
* need to allocate and use the heap data structure.
*
* @param target target point
* @param maxDistance maximum distance
* @param result information about the nearest point (output parameter)
* @return true if a nearest point was found within maxDistance
*/
private boolean searchNearest(
final double[] target, double maxDistance, NnData<PointData> result) {
if (root == null) {
return false;
}
double tau = maxDistance;
final FastQueue<Node> nodes = new FastQueue<Node>(20, Node.class, false);
nodes.add(root);
result.distance = Double.POSITIVE_INFINITY;
boolean found = false;
while (nodes.size() > 0) {
final Node node = nodes.getTail();
nodes.removeTail();
final double dist = distance(items[node.index], target);
if (dist <= tau && dist < result.distance) {
result.distance = dist;
result.data = itemData[node.index];
result.point = items[node.index];
tau = dist;
found = true;
}
if (node.left != null && dist - tau <= node.threshold) {
nodes.add(node.left);
}
if (node.right != null && dist + tau >= node.threshold) {
nodes.add(node.right);
}
}
return found;
}