[mkgmap-dev] [Patch v3] LocationHook with new Quadtree

Fri Jan 13 17:23:30 GMT 2012

>  > > >
>  > > > * I don't understand why you need a merge() method. Could you explain
>  > > > what you are doing in this method and why it's required?
>  > > The get method() of the tree returns the data for the first area that
>  > > contains the coord.
>  > > This area should contain all tags of the area itself plus those from
>  > > areas intersecting it.
>  > > Maybe this is not correct?
>  >
>  > Sounds wrong. If Area a1 is intersected by a2 only in 10% of its area
>  > then an element located in the 90% that does not intersect would be
>  > tagged with a1 and a2?
>  >
> The merge() first creates a new nodeElem with the intersection, it
> merges the tags into this
> and subtracts the intersection from the others, so only the 10% part
> gets more tags.
> Thinking again about this I might not need both subtract() calls since I
> move the intersection part
> before the others .
>

I doubt that merge improves the performance. It breaks two areas into 
three probably with intersecting bounding boxes. So I would expect that 
you don't save much contains checks.
But don't mind about my doubts: Did you measure a noticeable performance 
difference?

WanMil