[GraphHopper] Does Graphhopper merge ways with equal flags and name?

[Peter]

Hi,

there is no separate merging logic (although there was in 0.1 or
something). In OSMReader it is decided when an edge is created and e.g.
OSM ways are splitted if there are barriers or junctions on the way. So
it decides whether an osm nodes will be a tower node or just a pillar node

Regards,
Peter

On 03.06.2015 20:35, John Zhao wrote:
> Hi Peter,
>
> Could you tell me where is the merging logic?
> That's interesting.
>
> *Best Regards,*
> *ZhiQiang ZHAO*
>
> On Wed, Jun 3, 2015 at 12:09 AM, Peter <graphhopper at gmx.de
> <mailto:graphhopper at gmx.de>> wrote:
>
>     Hi Jan,
>
>     we do this kind of 'merging' logic already in the import step when
>     deciding what should be handled as tower node and what is a pillar
>     node. Otherwise you'll need as twice as many RAM when copying from
>     one graph to the other.
>
>
>     > Have you made a experiment to count the number of 2 degree nodes with the equal flags and name in OSM?
>     > And then we can know how many edges we can save.
>
>     Yes, this should be done before implementing it :)
>
>     And as the merging logic is currently not 100% optimal, there
>     could be some minor savings even when recognizing the different
>     street names, but I'm unsure if it is worth the effort.
>
>     Issues like #234 or #111 will probably make more difference.
>
>     Kind Regards,
>     Peter
>
>
>     On 02.06.2015 22:35, John Zhao wrote:
>>     Hi,
>>
>>     AFAIK, there is no this kind of merging logic here.
>>     Wait the answer from Peter.
>>     Probably you need to implement it by your own.
>>     And it's not easy. 
>>     Maybe can be done before import?
>>     What you want, is actually convert a tower node to a pillar node.
>>
>>
>>     *Best Regards,*
>>     *ZhiQiang ZHAO*
>>
>>     On Tue, Jun 2, 2015 at 1:27 PM, Jan Torben Heuer <jan at komoot.de
>>     <mailto:jan at komoot.de>> wrote:
>>
>>         Hi ZhiQiang ZHAO,
>>
>>         Thanks for your quick answer.
>>         I have a custom FlagEncoder that imports only very few ways
>>         and I don’t need the names. I guess, I have mostly nodes with
>>         a degree of two.
>>
>>         Jan
>>
>>         Am 02.06.2015 um 21:53 schrieb John Zhao <johnthu at gmail.com
>>         <mailto:johnthu at gmail.com>>:
>>
>>>         Hi,
>>>
>>>         Have you made a experiment to count the number of 2 degree
>>>         nodes with the equal flags and name in OSM?
>>>         And then we can know how many edges we can save.
>>>
>>>         I doubt this should be not too much for OSM.
>>>
>>>         *Best Regards,*
>>>         *ZhiQiang ZHAO*
>>>
>>>         On Tue, Jun 2, 2015 at 11:59 AM, Jan Torben Heuer
>>>         <jan at komoot.de <mailto:jan at komoot.de>> wrote:
>>>
>>>             Hi,
>>>
>>>             Can Graphhopper merge two ways with equal flags and name
>>>             if there is no intersection between them (no third way
>>>             connected)?
>>>
>>>             I would like to create a very reduces graph with only
>>>             few edges. What would be the easiest way to achieve it?
>>>             I think I would have to disable the nameIndex for instance.
>>>
>>>             Thanks,
>>>
>>>             Jan
>>>
>

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