[GraphHopper] question on contraction

[Peter K]

Hey,

> I was wondering if you could give me some hint with respect to the
> parameters of the contraction algorithm.
>
> I'v identified the following parameters:
> * periodicUpdates  The higher the values the longer the preparation
> takes but the less shortcuts are produced.
> * lazyUpdates
> * neighborUpdates
>
> Can you hint me on the effect of the two last parameters on the speed
> of the contraction algorithm, and on the quality of the resulting
> contraction?

Increasing them will probably speed up the query a bit but increase
preparation time. You can play around with them easily:

./graphhopper.sh measurement <your osm file>

You'll get 3 important numbers: number of shortcuts (~size of the
graph), duration of the contraction and mean query time

You can easily change those values in the config.properties and run
another measurement session.

Regards,
Peter.