[GraphHopper] Cannot flush graph

[Peter]

Hi Tuan,

the speed is internally stored in just a few bits of the long value
(edgeState.getFlags)

And to convert this for that we divide speed through the specified
factor and use maximum 'speedBits' for the speed. E.g. 5 bits => 32
values => *5 => max speed of 160
So if you want a speed factor of 1 you need like 7 to 8 bits. Another
idea could be to have a table lookup instead of the factor to make it
more precise and compact at the same time.

Kind Regards,
Peter

On 03.07.2015 09:36, Tuan Nguyen wrote:
> Hi Peter,
>
> Thanks for the clarification on speed unit.
>
> My validation logic was to check if getSpeed() in current graph
> EXACTLY match the double value that I set before. This usually does
> not match as you said, "due to the limited resolution".
>
> Btw, can you elaborate a bit on the use of speedBits, speedFactor when
> storing speed? I know how to update speed through your blog posts but
> I cannot understand internally how it works. Or if you can point me to
> another resource, that would be much appreciated.
>
>
> Kind Regards,
> Tuan.
>
> On 3 July 2015 at 17:21, Peter <graphhopper at gmx.de
> <mailto:graphhopper at gmx.de>> wrote:
>
>     Hi,
>
>     good that you solved the problem but would you elaborate a bit on
>     this:
>     "They are always different as the way Graphhopper processes double
>     value."
>
>     Do you mean that getSpeed returns two different values before and
>     after flush? Or just the speed you are expecting vs. what getSpeed
>     returns - then, yes this is expected due to limited resolution
>     which you can tune in the flagencoder.
>
>     And the speed is km/h ... We even do not support mile in the UI (yet)
>     https://github.com/graphhopper/graphhopper/issues/396
>
>     Peter
>
>
>     On 03.07.2015 07:53, Emux wrote:
>>     On 03/07/2015 05:12 πμ, Tuan Nguyen wrote:
>>>     By the way, is the speed used in Graphhopper km/hour or mile/hour?
>>
>>     I expect it to be units based on the SI system.
>>
>>     -- 
>>     Emux
>>     Cruiser <http://wiki.openstreetmap.org/wiki/Cruiser> - Atlas
>>     <http://wiki.openstreetmap.org/wiki/Atlas_%28navigation_application%29>
>

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