[GraphHopper] There must be bug on the subnetwork removal

Tue Jul 28 18:05:56 UTC 2015

Hi Peter,

the result I posted is not the result of oneway-subnetwork procedure.

The total procedures include:
1. remove zero-degree node
2. findSubnetwork
3. oneway-subnetwork procedure
4. findSubnetwork again on graphhopper.cleanup()

My question is, why those islands are recognized on step 4, but not on step
2?

*Best Regards,*
*ZhiQiang ZHAO*

On Tue, Jul 28, 2015 at 12:02 AM, Peter <graphhopper at gmx.de> wrote:

>  Hi ZhiQiang,
>
> I think it is because both networks are oneway subnetworks not found by
> the normal subnetwork procedure (but by the oneway-subnetwork procedure)
> and you defined the oneway minimum size to 20
>
> Regards,
> Peter
>
>
> On 28.07.2015 03:13, John Zhao wrote:
>
> Hi Peter,
>
>  What I do is:
> 1. minOnewayNetworkSize = 20, minNetworkSize = 200
> 2. build san francisco bay area osm data
> 3. I print out the subnetworks result of the second call.
>
> int remainingSubnetworks = preparation.findSubnetworks().size();
>
> 4. I found the subnetwork has some smaller than 200, like:
>
> subnetwork start from: 37.32611992939085,-121.9961998312816 size: 24
>
> subnetwork start from: 37.78373608999855,-122.25065187925067 size: 34
>
>  5. I can't understand why the subnetworks with 24 nodes and 34 nodes are not removed by preparation.doWork();
>
> It call the same method:
>
> Map map = this.findSubnetworks();
>
>
>  *Best Regards,*
> *ZhiQiang ZHAO*
>
> On Mon, Jul 27, 2015 at 12:54 PM, Peter <graphhopper at gmx.de> wrote:
>
>>  Hi John,
>>
>> sorry, I do not understand your problem or question here. Would you
>> describe it again step by step for me :) ?
>>
>> Kind Regards,
>> Peter
>>
>>
>> On 27.07.2015 21:45, John Zhao wrote:
>>
>> Hi Peter,
>>
>>  Thanks.
>> Actually I only have 1 flagEncoder in the EncodingManager.
>> The call is exact same, preparation.findSubnetworks()
>>
>> preparation.findSubnetworks() using edgeFilter which is also from singleEncoder.
>>
>>
>>  *Best Regards,*
>> *ZhiQiang ZHAO*
>>
>> On Sun, Jul 26, 2015 at 7:56 AM, Peter <graphhopper at gmx.de> wrote:
>>
>>>  Hi John,
>>>
>>> it should not be related to calling these method twice. It is just one
>>> time where you calculate the subnetworks independent of any FlagEncoder or
>>> direction via findSubnetworks and the second pass is FlagEncoder- and
>>> access-dependent via removeDeadEndUnvisitedNetworks.
>>>
>>> Regards,
>>> Peter
>>>
>>>
>>> On 24.07.2015 21:16, John Zhao wrote:
>>>
>>> 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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