Guillaume,
Yes, that's basically correct, you've understood the rough structure. We
typically call the first graph, that looks like OSM, the "node-based-graph".
The graph that models all turns is referred to as the "edge-based-graph".
Somewhat confusing terminology, I know.
The edge-based-graph edge weights are measured in deci-seconds. Everything
is routed based on travel time.
The "speed * length" calculation happens slightly earlier in the process:
https://github.com/Project-OSRM/osrm-backend/blob/develop/extractor/extraction_containers.cpp#L323-L337
<https://github.com/Project-OSRM/osrm-backend/blob/develop/extractor/extraction_containers.cpp#L323-L337>
Unfortunately, the terminology used "distance/weight" is not consistent
across the codebase, so it can be difficult to navigate. Suffice to say, the
traffic penalty is adding "deci-seconds" to the edge-based-edge-weight.
To do per-node penalties, you would need to add a lookup table for each node,
populate it, probably in the "node_function" in the Lua profile, then consult
the lookup in the same place the traffic light penalty is currently added.
daniel
> On Oct 21, 2015, at 2:26 PM, Guillaume Barreau <[email protected]> wrote:
>
> Thanks Daniel and Patrick for your help,
>
> I will have to pick your brains a little bit more I am afraid.
>
> Having read this page:
> https://github.com/Project-OSRM/osrm-backend/wiki/Graph-representation
> <https://github.com/Project-OSRM/osrm-backend/wiki/Graph-representation>
>
> I now understand that what OSRM models as a node is actually what I initially
> thought of as an edge (i.e. a piece of road connecting 2 intersections) and
> what OSRM calls an edge is a transition from one road segment (travelled in a
> particular direction) to another, so the edge ends up being a way of crossing
> a road intersection. This is kind of confusing at first, but I can see the
> benefits of doing that way in terms of handling intersections well. Please
> correct me if I haven't understood properly.
>
> So in my case, the penalty would be associated with edges and not nodes. And
> all edges associated with the same physical interesection would get the same
> penalty (although this way of modelling has the advantage of allowing each
> turn to have a different penalty easily).
>
> The code you pointed me to is called at the graph preparation phase, right?
> That is fine for my purposes, I am just clarifying.
>
> This distance variable that is incremented it ends up representing the total
> penalties associated with crossing that particular intersection in a
> particular way and I assume it gets stored as the attribute of the
> corresponding edge in the graph. I was curious of when and how this distance
> (a penalty expressed in meters) then gets converted back into a time.
>
> Thanks a lot for your time again,
>
> Guillaume
>
>
>
> On 21 October 2015 at 15:56, Daniel Patterson <[email protected]
> <mailto:[email protected]>> wrote:
> Thanks Patrick, yes, that was what I meant to point at :-)
>
> > On Oct 21, 2015, at 12:44 PM, Patrick Niklaus
> > <[email protected] <mailto:[email protected]>>
> > wrote:
> >
> > Hey Guillaume,
> >
> > I think Daniel wanted to post a link to this line:
> >
> > https://github.com/Project-OSRM/osrm-backend/blob/develop/extractor/edge_based_graph_factory.cpp#L417
> >
> > <https://github.com/Project-OSRM/osrm-backend/blob/develop/extractor/edge_based_graph_factory.cpp#L417>
> >
> > All you need to do is to adapt the code to not only add penalties for
> > traffic signals but also your node.
> > Actually this code should be made more general as outlined in
> > https://github.com/Project-OSRM/osrm-backend/issues/1490
> > <https://github.com/Project-OSRM/osrm-backend/issues/1490>
> >
> > Best,
> > Patrick
> >
> >
> > On Wed, Oct 21, 2015 at 9:02 PM, Guillaume Barreau <[email protected]
> > <mailto:[email protected]>> wrote:
> >> Hi Daniel,
> >>
> >> Thanks a lot for this very fast reply. The url you sent appears to be
> >> broken. Could you please double-check it for me?
> >>
> >> Thanks again,
> >>
> >> Guillaume
> >>
> >> On 21 October 2015 at 14:56, Daniel Patterson <[email protected]
> >> <mailto:[email protected]>> wrote:
> >>>
> >>> Hi Guillaume,
> >>>
> >>> There is a function called for every node:
> >>>
> >>>
> >>> https://github.com/mapbox/inrix-processing/blob/master/regions.json#L198-L201
> >>>
> >>> <https://github.com/mapbox/inrix-processing/blob/master/regions.json#L198-L201>
> >>>
> >>> however, it doesn't feed back any specific per-node penalties. It's
> >>> used to flag barriers and traffic lights right now.
> >>>
> >>> It could be adapted to do per-node penalty values, you would probably
> >>> need to modify the existing light penalty functionality and add a lookup
> >>> for
> >>> your values, rather than using the global light penalty we have currently.
> >>>
> >>> daniel
> >>>
> >>> On Oct 21, 2015, at 11:46 AM, Guillaume Barreau <[email protected]
> >>> <mailto:[email protected]>>
> >>> wrote:
> >>>
> >>> Hello,
> >>>
> >>> I would like to OSRM for a research project but I have this unusual
> >>> requirement. I would want to be able to add time penalties at some sets of
> >>> vertices (defined by their id) that would be used to compute the fastest
> >>> routes in a table calculation. My input would therefore be a list of
> >>> (node_id,delays) to be added to the underlying graph. Is this feasible? I
> >>> am
> >>> prepared to modify the code if needs be, I don't expect to be able to do
> >>> this with a config file. If it is feasible, could someone point me in the
> >>> right direction?
> >>>
> >>> Thank you very much for your help,
> >>>
> >>> Guillaume
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> >>> <https://lists.openstreetmap.org/listinfo/osrm-talk>
> >>>
> >>>
> >>>
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> >>
> >>
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