[GraphHopper] How to ­­consider traffic jam whe­n­ route on road network

[Nicolas Gillet]

Hello,

It could work but I think that this will get the routing algorithm even slower.
Add this to the drop of contraction your performances would get really poor I’m afraid.

Nicolas GILLET


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De : lanmaster at hotmail.ru [mailto:lanmaster at hotmail.ru]
Envoyé : lundi 6 janvier 2014 12:17
À : Nicolas Gillet
Cc : GraphHopper Java routing engine; Jrgen Zornig
Objet : Re: Re: [GraphHopper] How to ­­consider traffic jam whe­n­ route on road network

Hello, Nicolas,

Why do I need to change any edge's weight?
My thought is about make no change in the graph data, but parallel calculate my own weights and use that in algorithm-place, where gets original Graph's weights.
May be my things was incorrect, please explain me.

Пнд 06 Янв 2014 16:05:06 +0500, Nicolas Gillet <nicolas.gillet at market-ip.com<mailto:nicolas.gillet at market-ip.com>> написал:

Hello guys,



That implementation won’t be efficient I think.

First thing you must know about using real time weighting is that you won’t be able to use contractions hierarchies unless you re-contract the whole graph any time you change any edge’s weight.

Without contraction you’ll have a serious downgrade of performances.



If you still want to perform real time weighting, the best option is to update the edge’s weight with your live traffic info, so updating the flags.



> 1.) Which flags are included and which position they are set?
This depends on the flag encoders you use, check the CarFlagEncoder class.



> 2.) Is there a convinient way to get a single EdgeIteratorState Object directly by poviding its ID?

If you know it’s GraphHopper’s ID, you can do graph.getEdgeProps(edgeId, Integer.MIN_VALUE) but you’ll have to maintain a way to link OSM ID’s with GH’s ids.



Regards,



Nicolas GILLET





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De : lanmaster at hotmail.ru<mailto:lanmaster at hotmail.ru> [mailto:lanmaster at hotmail.ru]
Envoyé : lundi 6 janvier 2014 11:47
À : Jrgen Zornig
Cc : GraphHopper Java routing engine
Objet : Re: [GraphHopper] How to ­consider traffic jam when­ route on road network?



Hello, Jrgen!

I think about this implementation:
1. We have in-memory arraylist, that contains infos about traffic jam
2. We have function that can calculate weight of way by two coordinate pairs (from node / to node)
3. We have modification on Graphhopper's route calculate algorithm, that can request weight from our weight function (2) and summarize it with original Graphhopper's weight.

Can that implementation be useful, how do you think?


Пнд 06 Янв 2014 15:16:52 +0500, Jrgen Zornig <juergen.zornig at gmail.com</compose/?adb_to=juergen.zornig at gmail.com>> написал:

I am also trying to figure out how real time graph modifications and short and temporary events should be handled for the routing.

I assume you use to OSM graph? That makes things more complicated I think,because I have not found a function to retrieve a single Edge without iterating over and over the whole graph. Even when you know the Edge Id, you have to iterate over all Edges.

In our scenario, we use a different (our own) graph, and while loading it, I build up a HashMap for all EdgeIteratorState Objects I have generated during loading. So I can easily find a corresponding Edge for a given TrafficJam, either by directly referencing it over our EdgeIds or by finding out the Id via the LocationIndex (NodeIds and the referenced EdgeIds).

When having the corresponding EdgeIteratorState Object it should be simple to deactivate the Edge by calling setFlags(), but I also have no clue yet, how to set this bitmask because I couldn't find any documentation on to flags itself.

So I want to add to this question:

1.) Which flags are included and which position they are set?
2.) Is there a convinient way to get a single EdgeIteratorState Object directly by poviding its ID?

I am in need of these functions to handle real time traffic data on the graph.

P.S. Perhaps we can figure it out by ourselves, so Peter doesn't have to answer every single question ;)

Regards,

Juergen

Am 06.01.2014 09:54, schrieb lanmaster at hotmail.ru</compose/?adb_to=lanmaster at hotmail.ru>:

Graphhopper is a project for finding routes over a road network. It also provides functionality for weighting this routing like fastest or shortest path e.g. via the FastestWeighting class. Now, the question is: how can we extend Graphhopper to use the speed data we get from our traffic provider in realtime?

As I can see:

  1.  We must create a function that gets traffic jam data from our database.
  2.  We must force use that modified function (Encoder?) somewhere in Graphhopper route() function. Do I think right?

Please show me how we can do this by example.



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