[GraphHopper] Potential problem with contractions in turn cost

[Peter K]

>
> (I've sent this mail to
> reply+i-24834155-b934533b0af3ded2f59a77048d6073f5c7a2c5b1-1106958 at reply.github.com
> but it is not showing up on the mailing list, so I send it again,
> directly to the graphHopper mailing list)

This OSM mailing list is not yet associated with github ;)

> I was reading the code regarding turn cost found at:

Turn costs are not yet implemented in GraphHopper but are coming:

https://github.com/graphhopper/graphhopper/pull/55#issuecomment-31089096

So there cannot be a bug ;)

> I therefore believe that the criterion for adding a shortcut a-b when
> contracting c should be the following

Thanks for investigating this! Are you referring to turn restrictions
with a way as 'via' parameter? Then yes, such changes could be necessary
indeed. But currently we are focusing on turn costs for none-CH, then
including CH, but still only via a node not a way. Later on we'll of
course add this more detailed turn stuff.

Regards,
Peter.


>
> if
> for any incoming edges to a called I (eg: w-a, and y-a)
>     for any outgoing edge from b called O (eg: b-x, and b-z)
>         the path I-a-c-b-O is the strictly cheapest one binding I to O
> then
>             then a shortcut must be added
>
> This criterion is more expensive to compute, and I believe that it is
> also a bit more demanding, that is: more shortcuts might be added.
>
> -- 
> *Renaud De Landtsheer, Ir, Phd*
> Sr R&D Engineer
> CETIC
> Rue des Frères Wright, 29/3
> B-6041 Charleroi
> Phone: +32 71 490 754
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>
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