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

[Peter]

Hi,

the details are a bit trickier as we do everything very memory efficient.

And if a osm node occurs twice it is a pillar node, otherwise it is a
tower node.

Kind Regards,
Peter

On 03.06.2015 21:05, John Zhao wrote:
> I go through the logic:
> It go through all osmways, and count the occurrence of nodeID.
> if nodeID appear only once, it's a pillar node.
> otherwise, it's a tower node.
>
> That's it. Do I miss something?
>
>
> *Best Regards,*
> *ZhiQiang ZHAO*
>
> On Wed, Jun 3, 2015 at 11:55 AM, Peter <graphhopper at gmx.de
> <mailto:graphhopper at gmx.de>> wrote:
>
>     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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