[OSM-dev] Multithread generate_tiles.py, generate_images.py and question about attribution.

Radek Bartoň blackhex at post.cz
Mon Oct 5 14:57:35 BST 2009


Dne neděle 04 Říjen 2009 05:09:51 Dane Springmeyer napsal(a):

> I meant to ask if you had yet compared your generate_tiles.py
> threading support to the recent additions in svn?
> 
> I assume not since you wrote yours, as you say several months ago, but
> it would be interesting to test the speed of each version.

Now I tried and the results are quite interesting. I tested on 3GHz Intel Core 
2 Duo machine with 2GB RAM and using 2 threads.

Result for OpenStreetMap generate_tiles.py was:

real 42m10.608s
user 21m39.037s
sys 4m36.265s

Result for OpenTrackMap (mine) generate_tiles.py was:

real 56m57.562s
user 32m7.568s
sys 8m24.184s

Then I noticed that OSM version doesn't use any overlapping. When I removed 
overlapping from mine version the result (even when full color version of tile 
is stored to the disk and then converted to 256 color version using 
ImageMagick) was:

real 40m35.201s
user 21m42.249s
sys 6m42.197s

Anyway, OSM version should use some overlapping because then there are some 
artifacts on tile borders. Maybe the best solution would be to render for 
example 16x16 (or more) tiles image with small border and then cut the image 
to separated tiles. This could bring also another performace gain because of 
better memory utilization or less access to DB.

Mine version has small benefit compared to OSM version - it can be interrupted 
with CTRL+C keys, while mine version doesn't use job queue so it probably 
doesn't scale as well as OSM version.

-- 
Ing. Radek Bartoň

Faculty of Information Technology
Department of Computer Graphics and Multimedia
Brno University of Technology

E-mail: blackhex at post.cz
Web: http://blackhex.no-ip.org
Jabber: blackhex at jabber.cz




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