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[mkgmap-dev] Bug in LocationHook?

From Gerd Petermann gpetermann_muenchen at hotmail.com on Sun Jan 8 16:47:36 GMT 2012

Hi WanMil

> I remember that I tried the other strategy. I don't remember how I did 
> organize the boundaries. But it was *magnitudes* slower (not just slower 
> but magnitudes slower) so that I didn't started to improve my poor 
> implementation.

I tried it anyway and found some interesting results:
Sometimes it is ~ 20% faster, sometimes it is much slower (maybe 100% ). So, I think it might be a good alternative if we can avoid the bad cases.

I created a simple grid that stores all boundaries that intersect with each element (similar to the grid in splitter). This is done quicker than the creation of the quadtree.
Using the grid, for each Coord I get a list of boundaries to test:
                Boundary b = currentBoundaries.get(blist.get(i));
                if (b.getBbox().contains(co)){
                    if (b.getArea().contains(co.getLongitude(),co.getLatitude())){
                        return b; // return the area that contains the point                    }

the performance problem is in the b.getArea().contains(...)
For some boundaries, this test performs very slowly (> 1ms for one test), and it seems to be related to the number of points that form the shape of the boundary.
Some areas are built with < 20 points, others with > 8000. 

So, what I need is a quicker contains() or some kind of tree that allows to avoid it. 
Any idea?


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