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[mkgmap-dev] tile takes very long time to generate

From Gerd Petermann gpetermann_muenchen at hotmail.com on Tue Mar 9 15:27:09 GMT 2021

Hi all,

I sea no easy way to fix this. We'll have more and more monster multipolygons like r9488835. The current code in mkgmap r4607 processes a type=multipolygon before any rule from relations is used, so there is no easy way to tell mkgmap to ignore any MP with place=sea.
Using a program like osmfilter on complete countries or continents also takes time, so maybe the best place to filter these killers would be in splitter, but we probably need some flexible syntax similar to the style rules.
Another option would be a new mkgmap rule file for mkgmap that would be processed after reading the MP but before processing its geometry. This new rule file could allow actions like those in the finalize section of points/polygons.

Any ideas besides hard coded "quick&dirty" solutions?


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Bernhard Hiller <bhil at gmx.de>
Gesendet: Dienstag, 9. März 2021 09:50
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] tile takes very long time to generate

Hi Karl,
some time ago, I stumbled upon a tile which took 2 hours(!) on my machine.
With the "--polygon-file" option, the time could be reduced to less than
100 s.
See the old message in the archive:
and the thread "Performance with large files":
Perhaps the trick helps in your case, too.
Kind regards,

Am 08.03.2021 um 06:53 schrieb 7770:
> Hi.
> I observe a situation that one of the very first tiles (often the first or the
> third) that mkgmap generates takes 20 - 30 minutes to generate, wheres the
> others take about 30 seconds each.
> The map data produced by splitter is a total of around 700 files with splitter
> option --max-nodes=1275000.
> sea and bouds are used for mkgmap.
> At first i thought i am running low on memory but changing to max-jobs=1
> (instead of the possible max of 2) did not make any change.
> Is mkgmap doing something specific in the beginning that can explain this long
> time generating one of the very first tiles?
> I can provide more details, let me know how i can best collect those details
> in case i need to set some parameters to have mkgmap to say more about what it
> is doing.
> Regards
> Karl

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