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

[John Zhao]

Hi Peter,

That sounds reasonable. But I am still confused.
I think the logic is under the below logic.
Based on the logic and commets, a node is "mark node as tower node as it
occured at least twice times", not "at least 3 times".

    void prepareHighwayNode( long osmId )

    {

        int tmpIndex = getNodeMap().get(osmId);

        if (tmpIndex == EMPTY)

        {

            // osmId is used exactly once

            getNodeMap().put(osmId, PILLAR_NODE);

        } else if (tmpIndex > EMPTY)

        {

            // mark node as tower node as it occured at least twice times

            getNodeMap().put(osmId, TOWER_NODE);

        } else

        {

            // tmpIndex is already negative (already tower node)

        }

    }

*Best Regards,*
*ZhiQiang ZHAO*

On Wed, Jun 3, 2015 at 12:15 PM, Peter <graphhopper at gmx.de> wrote:

>  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> 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> 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> 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>:
>>>>
>>>>  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>
>>>> 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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