[OSRM-talk] OSRM 5.14.3 set kilometers long ways as small elements

[Daniel Patterson]

Hi François,

  Yes, oneways onto your custom road network sound like exactly the kind of
thing that the small component algorithm (
https://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm)
would flag.  If your custom network is <1000 nodes, it would've been
flagged previously.

  If you are only routing from the normal network *onto* your custom
network, then changing the component size like you've done is the correct
fix here.  Just be aware, if you start on your custom network, and try to
return to the main network, you will get "NoRoute" errors, but it sounds
like that won't be a problem for you.

  I'm not sure what's up with the turn icons in the debug viewer - make
sure you've zoomed in far enough, turn icons only show up from Z12 and
higher.

daniel

On Mon, Mar 26, 2018 at 10:22 AM, François Lacombe <
fl.infosreseaux at gmail.com> wrote:

> Hi Daniel,
>
> I didn't know this really nice option small-component-size :)
> I set it to 10 and many so tagged small elements weren't small any more.
>
> Routing engine use these ways again, which solve my problem, thank you
>
> This means I didn't have any connectivity problems, and oneway/turn
> restrictions wasn't too restrictive.
> Then, why disabling access to small elements, especially when they can
> provide a way more efficient route?
>
> My graph is a bit special, and I would understand osrm will have issues to
> browse it.
> I have custom ways linked to standard road network with oneway edges
> toward my custom ways.
> Then once you get in my parallel network, you can't get out back to the
> standard roads.
> Do oneway edges get lower rate or whatever ?
> My oneway handler set is_forward_oneway=true and backward_mode=mode.
> innacessible
>
> Finally, I don't see any turn icon around my connections on debug render
> (despite the style is well installed in debug/index.html), should I worry?
>
>
> Kind thank you for your answers
>
> François
>
> 2018-03-26 19:01 GMT+02:00 Daniel Patterson <daniel at mapbox.com>:
>
>> Hi François,
>>
>>   The small component behaviour happens when a section of the graph is
>> disconnected from the rest.  I can think of a few possible reasons you're
>> seeing this:
>>
>>     1. Your road isn't actually connected
>>     2. Turn restrictions or one-ways are preventing access to both ends
>> of the road
>>     3.  Your map is really small - by default, isolated groups of <1000
>> nodes are flagged as separate "small components".  If your total map is
>> <1000 nodes, then you'll probably get the whole thing flagged.  You can
>> adjust by passing the `--small-component-size` parameter to
>> `osrm-extract`.  Setting it to `--small-component-size 0` will mean that no
>> roads are marked as small, and snapping will all be to the nearest
>> neighbour.
>>
>> If you use 3, note that it won't fix connectivity problems - even though
>> using `--small-component-size` will change what is used to snap, if there
>> is actually no route to a location (and the small component analysis is
>> indicating that there may not be), you will get `NoRoute` API responses.
>>
>> daniel
>>
>> On Mon, Mar 26, 2018 at 9:46 AM, François Lacombe <
>> fl.infosreseaux at gmail.com> wrote:
>>
>>> Hi,
>>>
>>> As mentionned in the mail title, OSRM 5.14.3 is defining kilometers long
>>> ways as small which are seen with a purple casing in the debug view.
>>> I read this view may be buggy, and I don't see those ways in small layer
>>> of standard osrm-frontend.
>>>
>>> Nevertheless, osrm-routed won't use the path, despite it has a really
>>> good speed and rate.
>>> My profile was written from scratch, I can't publish it actually and I'm
>>> not allowed to publish a data extract (part of my client dataset)
>>>
>>> Furthermore, I have similar ways, with same weight, rate and speed which
>>> aren't seen as small and used by the routing engine really well.
>>>
>>> Here are the properties I get from process_way lua function :
>>> forward_mode = 3 (mode.walking)
>>> format_access = nil (both routable and not routable ways, should I have
>>> another value here?)
>>> weight = -1
>>> rate = 5
>>> speed = 45 (prefered path use rate=0.6 + speed = 0.1 ways)
>>>
>>> Is there any additionnal value I should watch to find why OSRM says I
>>> have small elements ?
>>>
>>>
>>> Any input is welcome regarding this issue, all the best
>>>
>>> François
>>>
>>> _______________________________________________
>>> OSRM-talk mailing list
>>> OSRM-talk at openstreetmap.org
>>> https://lists.openstreetmap.org/listinfo/osrm-talk
>>>
>>>
>>
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>
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