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

[Peter]

Hi Jan,

> Do you have a suggestion how I could do that?

That won't be easy without knowning what you intend to do. E.g.
barriers, different speeds or changing flags due to changed tagging on
the street: all will lead to 2 degree nodes. Different names is probably
only a minor thing as streets change names 'in the middle of a street'.

A simple post-processing procedure for your case could be to create
additional direct edges from junction to junction where you found a 2
degree node and mark the other edges as inaccessible.

Kind Regards,
Peter

On 03.06.2015 10:24, Jan Torben Heuer wrote:
> Hi Peter, 
>
> If there is already a merging logic, then I would  ‚only‘ have to
> disable the name parsing or nameIndex? Do you have a suggestion how I
> could do that? (If that is too difficult I could also remove all name
> tags from the osm file, I think).
>
> Just to be clear, my question has nothing to do with saving memory and
> stuff. That topic was brought up by ZhiQiang ZHAO. I just need a graph
> with edges from intersection to intersection.
>
> Thanks,
>
> Jan
>
>
> Am 03.06.2015 um 09:09 schrieb Peter <graphhopper at gmx.de
> <mailto:graphhopper at gmx.de>>:
>
>> 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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