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[mkgmap-dev] [PATCH v2] Performance improvement by removing unused elements before the style processing

From WanMil wmgcnfg at web.de on Wed Jan 4 18:10:28 GMT 2012

Hi Gerd,

yes of course I am interested, Send me all information you have.


> Hi WanMil,
> I tested the patch with my tiles for Saarland. I can confirm a reduction of
> processing time ~ 6% compared to r2160, and also a reduction for the peek
> value of heap memory usage (238M ->  210M), so that's both good!
> BUT I also see a difference in one of the seven output img files (plus the
> resulting gmapsupp.img), and I think this is not intended. Both files have
> the same size, but are different in many bytes.
> Let me know when I should send details, maybe the new result is better than
> the old ;-)
> Ciao,
> Gerd
> WanMil wrote
>> The 2nd patch fixes the remaining problems:
>> 1. Ways without tags but referenced by relations are no longer removed
>> (they might be tagged by the relation style file and could therefore
>> appear in the map)
>> 2. Intersection of ways with the tile bounding box is now checked
>> instead of only checking that at least one point is contained in the
>> bounding box. Only very few ways are affected by this but otherwise
>> routing problems are possible.
>> The performance improvement seems to be good (measured with my test map):
>> r2159: ~250s
>> patched: ~225s
>> I also expect (although I haven't tested) that the max memory
>> requirement of mkgmap is decreased. I think max mem is used when the
>> style file is just processed. At this stage all raw OSM elements and all
>> style file processed elements are kept in memory. With the patch the
>> number of OSM elements is noticeably reduced.
>> WanMil
>>> Hi,
>>> this is another performance improvement:
>>> Usually the mkgmap input tiles are larger than the processed bounding
>>> box (splitter parameter overlap). So there are much many elements which
>>> are processed but thrown away at a late step in mkgmap.
>>> The patch tries to remove them much earlier before the style files are
>>> processed and before the LocationHook starts (which ignores them but
>>> that must also be calculated).
>>> The patch contains one drawback:
>>> Ways which have all its points outside the bounding box of the tile but
>>> which cross the tile are also removed. If that's a point the patch must
>>> be improved.
>>> Have fun!
>>> WanMil
>>> _______________________________________________
>>> mkgmap-dev mailing list
>>> mkgmap-dev at .org
>>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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