[GraphHopper] 答复: About Intermediate Data

[Peter K]

Hey Pengzhan :),

there are papers about contraction hierarchies but also some video which
I can recommend (see wikipedia
<http://en.wikipedia.org/wiki/Contraction_hierarchies> for this).

In GraphHopper you need to read/understand the classes
PrepareContractionHierarchies and Path4CH. Roughly speaking: you create
shortcuts (additionally edges which avoid most of the nodes) recursivly.
And on query time you run a bidirectional Dijkstra where you afterwards
have to 'unfold'/'extract' those shortcuts into edges which is done in
Path4CH.

Regards,
Peter.



> Peter:
>
> If so, What basic speed-up method are you using for GH ?
>
> Please show me both algo and implement speed-up methods.
>
>  
>
> #P.s I can’t believe our gov block github again… and pls just call me
> Pengzhan
>
>  
>
> Best regards
>
> *发件人:*graphhopper-bounces at openstreetmap.org
> [mailto:graphhopper-bounces at openstreetmap.org] *代表 *Peter K
> *发送时间:*2014年4月25日19:19
> *收件人:*graphhopper at openstreetmap.org
> *主题:*Re: [GraphHopper] About Intermediate Data
>
>  
>
> Hey n  Pengzhan Hao,
>
> the graph files are (mostly) independent from the algorithm, they are
> just used to avoid the costly reparsing of the OSM file everytime you
> restart GraphHopper. The only difference is that CH creates some
> additional edges, so called shortcuts.
>
> The graph is organized as described here:
> https://github.com/graphhopper/graphhopper/blob/master/docs/core/quickstart-from-source.md#2-the-graph
>
> Regards,
> Peter.
>
>     Just focus on GH project , and interested in few questions:
>
>     It occurs to me that by using CHs algorithm ,several intermediate
>     data binary files appeared.
>
>     So what these files used for and how them organized in a data
>     structure?
>
>      
>
>     n  Pengzhan Hao
>
>      
>
>
>
>
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