[mkgmap-dev] Optimizing MapSplitter

Sat Nov 15 20:25:21 GMT 2014

Hi Steve,

> > I don't think that the current algo is completely wrong.
> > I think it is better to start with the complete data and divide it into
> > smaller parts as that algo keeps the information of
> > the location of elements, while your approach is likely
> > to compare many bboxes which are (too) far away from each other.
> 
> Yes, implementation speed might require some more complexity - but it
> seems that it should produce a division split where all of them are
> no bigger than required without further splitting the elements.

Maybe, but I don't think that this would be optimal,
as we may get too many sub divs and thus a much larger img 
file. I don't know how the device determines the
relevant sub divs, but even a good algo will suffer
if we produce 10000 instead of 250 sub divs.

> 
> If that is the case, and it still makes no difference in speed, then
> maybe we are pretty much as good as we are going to get.

I thought about writing an algo to test this, but that seems to be
even more complicated. I'd try to simulate the rendering 
for each element in a grid, and compare the number
of rendered elements (caused by overlaps) which 
are not visible in the grid element.
This could be done for each level, and maybe one
has to take into account that a device has to render
a rectangle which heads to north-west or west.

Gerd

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