[OSRM-talk] Route flapping / osrm-prepare adds randomness?
Florian Lohoff
f at zz.de
Tue Jun 30 10:45:42 UTC 2015
Hi,
i am doing QA based on calculating routes. For this i have a defined
set of points (couple hundret) which i calc routes between. On length
change i get a notification by email that the route has changed.
Now i see routes which regularly flap between 2 different geometries and
lengths without the OSM data beeing changed so i started investigating.
The route flap happens irregular when osrm-prepare'ing the same
germany.osm.pbf over an over. I see route flaps on same OSM data input.
What i typically do (pseudo code) every 30-60 Minutes:
while true; do
update-germany-file-with-osmupdate
osrm-extract -p car.lua germany.osm.pbf
osrm-prepare -p car.lua germany.osrm
restart-osrm-routed
calculate-routes-and-compare-lengths
done
Now i disabled the step of updateing the germany.osm file and i still
do see the route flaps. It seems osrm-prepare adds some randomness to
graph weights.
Here you can see a visual change in route. The route flapped from red
to green and back just be re-preparing the very same osm.pbf file:
http://osm.zz.de/routeqa/?rid=59464,59492
http://osm.zz.de/routeqa/?rid=59492,59571
Is this a known issue/side effect of the contracted hierarchies or
is this expected behaviour e.g. a real bug?
Flo
--
Florian Lohoff f at zz.de
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