private static TItem[] NearestNeighbour(BoundablePair <TItem> initBndPair, double maxDistance)
{
double distanceLowerBound = maxDistance;
BoundablePair <TItem> minPair = null;
// initialize internal structures
var priQ = new PriorityQueue <BoundablePair <TItem> >();
// initialize queue
priQ.Add(initBndPair);
while (!priQ.IsEmpty() && distanceLowerBound > 0.0)
{
// pop head of queue and expand one side of pair
var bndPair = priQ.Poll();
double currentDistance = bndPair.Distance; //bndPair.GetDistance();
/**
* If the distance for the first node in the queue
* is >= the current minimum distance, all other nodes
* in the queue must also have a greater distance.
* So the current minDistance must be the true minimum,
* and we are done.
*/
if (currentDistance >= distanceLowerBound)
{
break;
}
/**
* If the pair members are leaves
* then their distance is the exact lower bound.
* Update the distanceLowerBound to reflect this
* (which must be smaller, due to the test
* immediately prior to this).
*/
if (bndPair.IsLeaves)
{
// assert: currentDistance < minimumDistanceFound
distanceLowerBound = currentDistance;
minPair = bndPair;
}
else
{
// testing - does allowing a tolerance improve speed?
// Ans: by only about 10% - not enough to matter
/*
* double maxDist = bndPair.getMaximumDistance();
* if (maxDist * .99 < lastComputedDistance)
* return;
* //*/
/**
* Otherwise, expand one side of the pair,
* (the choice of which side to expand is heuristically determined)
* and insert the new expanded pairs into the queue
*/
bndPair.ExpandToQueue(priQ, distanceLowerBound);
}
}
if (minPair != null)
{
// done - return items with min distance
return new[]
{
((ItemBoundable <Envelope, TItem>)minPair.GetBoundable(0)).Item,
((ItemBoundable <Envelope, TItem>)minPair.GetBoundable(1)).Item
}
}
;
return(null);
}
private static TItem[] NearestNeighbour(BoundablePair <TItem> initBndPair)
{
double distanceLowerBound = double.PositiveInfinity;
BoundablePair <TItem> minPair = null;
// initialize search queue
var priQ = new PriorityQueue <BoundablePair <TItem> >();
priQ.Add(initBndPair);
while (!priQ.IsEmpty() && distanceLowerBound > 0.0)
{
// pop head of queue and expand one side of pair
var bndPair = priQ.Poll();
double pairDistance = bndPair.Distance;
/**
* If the distance for the first node in the queue
* is >= the current minimum distance, all other nodes
* in the queue must also have a greater distance.
* So the current minDistance must be the true minimum,
* and we are done.
*/
if (pairDistance >= distanceLowerBound)
{
break;
}
/**
* If the pair members are leaves
* then their distance is the exact lower bound.
* Update the distanceLowerBound to reflect this
* (which must be smaller, due to the test
* immediately prior to this).
*/
if (bndPair.IsLeaves)
{
// assert: currentDistance < minimumDistanceFound
distanceLowerBound = pairDistance;
minPair = bndPair;
}
else
{
/**
* Otherwise, expand one side of the pair,
* (the choice of which side to expand is heuristically determined)
* and insert the new expanded pairs into the queue
*/
bndPair.ExpandToQueue(priQ, distanceLowerBound);
}
}
if (minPair != null)
{
// done - return items with min distance
return new[] {
((ItemBoundable <Envelope, TItem>)minPair.GetBoundable(0)).Item,
((ItemBoundable <Envelope, TItem>)minPair.GetBoundable(1)).Item
}
}
;
return(null);
}
