[mkgmap-dev] splitter that generates problem list

Sun Nov 4 18:19:49 GMT 2012

Hi Henning,

if I got this right we have to save a list of tiles for each node of each
way and relation, or we have to do multiple reads for every tile. Saving the
list is not possible for planet on 32bit systems (planet contains more than
1.600.000 nodes  and more than 155.000.000 ways, and I guess that at least
half of the nodes is part of a way or relation. On 32bit systems we have
~1.6000.000 bytes for heap, so we have less than 2 bytes to store the id and
the list of writers. I don't see how this could be done.
Besides that your proposal might work, but it would be difficult to detect
enclosed tiles that have no node of a multipolygon relation.

Gerd

Henning Scholland wrote
> Am 04.11.2012 14:05, schrieb Gerd Petermann:
>> @ all: I need an algorithm that uses a list like below and fills "the 
>> rest of planet" with a small number of rectangles. There is no need to 
>> find the smallest number, but the result should be near.
> Another idea:
> 
> detect problematic polygons or read problematic-polygons.txt
> 
> read relations and copy with way-ids and node-ids to RAM
> read ways and copy node-id to RAM
> read nodes
>      is node in tile X?
>          check in RAM: does this node belong to a way or relation?
>              save this info somewhere (so you know, which ways and 
> relations should be written to a tile X and which way/node-ids are
> missing)
> read nodes again
>      is node in tile X?
>          write to tile X
>      is node missing in tile X?
>          write to tile X
> read ways
>      should it be written to tile X?
>          write it to tile X
> read relations
>      should it be written to tile X?
>          write it to tile X
> 
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