[mkgmap-dev] Performance with large files

Sun Mar 19 11:30:00 GMT 2017

Hi Bernhard,

if you see a different picture with the current version, please let me know.
One effect that might cause longer run time for later processed tiles is the String.intern()
method or Gargabe Collection in general.

Gerd
________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <GPetermann_muenchen at hotmail.com>
Gesendet: Sonntag, 19. März 2017 12:16:54
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] Performance with large files

Hi Bernhard,

the calculation time per tile can depend on map elements, e.g. complex multpolygons
may result in additional seconds. Besides that there should be a O(n) calculation time.
The final step however is typically to calculate the index , and that step reads data from
all tiles, so it depends on the amount of data.
Note the hint about --index in the help:
        If both the --gmapsupp and --tdbfile options are given alongside
        the --index option, then both indexes will be created. Note that
        this will require roughly twice as much memory.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Bernhard Hiller <bhil at gmx.de>
Gesendet: Sonntag, 19. März 2017 12:06:31
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: [mkgmap-dev] Performance with large files

How is mkgmap expected to behave when input files grow in size? Is a
linear inrease in calculation time - i.e. O(n) - expected, or an
increase beyond linearity?
E.g. when I create a map with routable lines for bicycle, mkgmap takes
some 30 minutes for Germany alone (3 GB pbf file resulting in 850 MB img
file), but more than  2 hours for Germany and some neighboring countries
(7 GB o5m file, resulting 1.4 GB img).
Are there many calculations at O(n^2) or beyond in mkgmap, or is this
due to other factors, e.g. memory limitation?
Notes:
mkgmap is called by
%JAVA% -Xmx6800M -ea -jar %MKGMAP% ....
on 64bit Win 7;
swapping to disc does not occur.
But I am more interested in a general rule than in some hints for
improving the performance in this concrete case. E.g. how I could
estimate the duration if I add some further countries...
Thanks for your hints.
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