private void KnnNodeSearch(
MNode <int> node,
T queryObject,
BoundablePriorityList <MNodeEntry <int>, double> nearestNeighboorList,
BoundablePriorityList <MNode <int>, double> priorityQueue)
{
foreach (var entry in node.Entries)
{
var maxPriority = nearestNeighboorList.MaxPriority;
if (node.IsInternalNode)
{
if ((node.ParentEntry == null) ||
(Math.Abs(
this.Metric(this.internalArray[node.ParentEntry.Value], queryObject)
- entry.DistanceFromParent) <= entry.CoveringRadius + maxPriority))
{
var distanceFromQueryObject = this.Metric(this.internalArray[entry.Value], queryObject);
var dMin = Math.Max(distanceFromQueryObject - entry.CoveringRadius, 0);
if (dMin < maxPriority)
{
priorityQueue.Add(entry.ChildNode, dMin);
var dMax = distanceFromQueryObject + entry.CoveringRadius;
if (dMax < maxPriority)
{
nearestNeighboorList.Add(null, dMax);
maxPriority = Math.Max(dMax, maxPriority);
priorityQueue.RemoveAllPriorities(p => p > maxPriority);
}
}
}
}
else if (Math.Abs(this.Metric(this.internalArray[node.ParentEntry.Value], queryObject) - entry.DistanceFromParent)
< maxPriority)
{
var distanceFromQueryObject = this.Metric(this.internalArray[entry.Value], queryObject);
if (distanceFromQueryObject < maxPriority)
{
nearestNeighboorList.Add(entry, distanceFromQueryObject);
nearestNeighboorList.RemoveAllElements(e => e == null);
maxPriority = Math.Max(distanceFromQueryObject, maxPriority);
priorityQueue.RemoveAllPriorities(p => p > maxPriority);
}
}
}
}
/// <summary>
/// A top-down recursive method to find the nearest neighbors of a given point.
/// </summary>
/// <param name="node">The index of the node for the current recursion branch.</param>
/// <param name="target">The point whose neighbors we are trying to find.</param>
/// <param name="rect">The <see cref="HyperRect{T}"/> containing the possible nearest neighbors.</param>
/// <param name="dimension">The current splitting dimension for this recursion branch.</param>
/// <param name="nearestNeighbors">The <see cref="BoundedPriorityList{TElement,TPriority}"/> containing the nearest neighbors already discovered.</param>
/// <param name="maxSearchRadius">The radius of the current largest distance to search from the <paramref name="target"/></param>
private void SearchForNearestNeighbors(
KDNode node,
double[] target,
HyperRect <double> rect,
int dimension,
BoundablePriorityList <int, double> nearestNeighbors,
double maxSearchRadius)
{
if (node == null)
{
return;
}
// Work out the current dimension
var dim = dimension % this.Dimensions;
// Get the coordinate of the current node.
var coordinate = this.PointSelector(this.InternalList[node.ElementIndex]);
// Split our hyper-rectangle into 2 sub rectangles along the current
// node's point on the current dimension
var leftRect = rect.Clone();
leftRect.MaxPoint[dim] = coordinate[dim];
var rightRect = rect.Clone();
rightRect.MinPoint[dim] = coordinate[dim];
// Determine which side the target resides in
var comparison = target[dim] <= coordinate[dim];
var nearerRect = comparison ? leftRect : rightRect;
var furtherRect = comparison ? rightRect : leftRect;
var nearerNode = comparison ? node.Left : node.Right;
var furtherNode = comparison ? node.Right : node.Left;
// Move down into the nearer branch
this.SearchForNearestNeighbors(
nearerNode,
target,
nearerRect,
dimension + 1,
nearestNeighbors,
maxSearchRadius);
// Walk down into the further branch but only if our capacity hasn't been reached
// OR if there's a region in the further rectangle that's closer to the target than our
// current furtherest nearest neighbor
var closestPointInFurtherRect = furtherRect.GetClosestPoint(target);
var distanceToTarget = this.Metric(closestPointInFurtherRect, target);
if (distanceToTarget.CompareTo(maxSearchRadius) <= 0)
{
if (nearestNeighbors.IsFull)
{
if (distanceToTarget.CompareTo(nearestNeighbors.MaxPriority) < 0)
{
this.SearchForNearestNeighbors(
furtherNode,
target,
furtherRect,
dimension + 1,
nearestNeighbors,
maxSearchRadius);
}
}
else
{
this.SearchForNearestNeighbors(
furtherNode,
target,
furtherRect,
dimension + 1,
nearestNeighbors,
maxSearchRadius);
}
}
// Try to add the current node to our nearest neighbors list
distanceToTarget = this.Metric(coordinate, target);
if (distanceToTarget.CompareTo(maxSearchRadius) <= 0)
{
nearestNeighbors.Add(node.ElementIndex, distanceToTarget);
}
}