[GraphHopper] There must be bug on the subnetwork removal

[John Zhao]

Hi Peter,

I am still confused.
at first we call
map = findSubnetworks();

after the cleanup, we call the same method in Graphhopper.

int remainingSubnetworks = preparation.findSubnetworks().size();


Why the subnetwork was recognized the latter time, but not the first time?

we remove some edges make it not connected?


*Best Regards,*
*ZhiQiang ZHAO*

On Thu, Jul 23, 2015 at 2:22 PM, Peter <graphhopper at gmx.de> wrote:

>
>  Hi ZhiQiang,
>
> yes, according to the wiki this is wrongly mapped:
> * Avoid tagging highway intersections as that does not make clear which
> way has the impediment. *
>
> http://wiki.openstreetmap.org/wiki/Tag:barrier%3Dgate
>
> Peter
>
>
> On 23.07.2015 23:16, John Zhao wrote:
>
> Hi Peter,
>
>  Maybe the following one related with
> https://github.com/graphhopper/graphhopper/issues/388#issuecomment-88066385
>
>
>  I have a look at 37.32611992939085,-121.9961998312816.
> It seesm related with barrier=gate at intersection.
> http://www.openstreetmap.org/node/1126492194
>
>  *Best Regards,*
> *ZhiQiang ZHAO*
>
> On Thu, Jul 23, 2015 at 2:11 PM, Peter <graphhopper at gmx.de> wrote:
>
>>
>>  There are two types of subnetworks and the smaller ones seems to be
>> 'one-way subnetworks' which means they are eg. only reachable as
>> destination or start. But if you would start from a destination-only
>> subnetwork you'll get 'not found' for all points outside of this network.
>>
>> Regards,
>> Peter
>>
>>
>> On 23.07.2015 23:03, John Zhao wrote:
>>
>>  Interesting,
>> when I increase minOnewayNetworkSize from 20 to 50, the following two
>> disappeared.
>>  subnetwork start from: 37.32611992939085,-121.9961998312816 size: 24
>> subnetwork start from: 37.78373608999855,-122.25065187925067 size: 34
>>
>>  *Best Regards,*
>> *ZhiQiang ZHAO*
>>
>> On Thu, Jul 23, 2015 at 1:55 PM, John Zhao <johnthu at gmail.com> wrote:
>>
>>> Hi,
>>>
>>>  I tried car flag encoder with following parameter on San Francisco bay
>>> area data from mapzen.
>>>
>>> https://s3.amazonaws.com/metro-extracts.mapzen.com/san-francisco-bay_california.osm.pbf
>>>
>>>  minNetworkSize=200
>>> minOnewayNetworkSize=20
>>>
>>>  I printed all the remaining subnetworks.
>>>  edges: 591932, nodes 437420, there were 3496 subnetworks. removed them
>>> => 13121 less nodes. Remaining subnetworks:5
>>> The remaining subnetworks are:
>>> subnetwork start from: 37.32611992939085,-121.9961998312816 size: 24
>>> subnetwork start from: 37.56018439442332,-122.30257814308803 size: 436637
>>> subnetwork start from: 37.78373608999855,-122.25065187925067 size: 34
>>> subnetwork start from: 38.180185962770565,-121.70631393878864 size: 301
>>> subnetwork start from: 37.85717050411933,-122.07633641532816 size: 424
>>>
>>>  I don't understand why there is still subnetwork less than 200 nodes.
>>>
>>>  I have a look at 37.32611992939085,-121.9961998312816.
>>> It seesm related with barrier=gate at intersection.
>>> http://www.openstreetmap.org/node/1126492194
>>>
>>>   *Best Regards,*
>>> *ZhiQiang ZHAO*
>>>
>>
>>
>
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