[mkgmap-dev] Performance with large files

Sun Mar 19 11:16:54 GMT 2017

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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