[Routing] Tools for getting from OSM to a routable network

[Nic Roets]

On Sat, Sep 20, 2014 at 10:59 AM, Geoff Leyland <geoff_leyland at fastmail.fm>
wrote:

>   That’s a lot of different areas to be expert in, and a pipeline that was:
>
>  - osm -> something you can work with through a configurable import
> process (SYCWW!)
>  - SYCWW -> various transformations (splitting, joining, simplifying,
> intersection expansion) -> SYCWW
>  - SYCWW -> mmapped binary format
>
> might mean that more people could get involved in their bit.  I’m aware
> that that’s kind of chasing unicorns, but you started it with your live
> updating router!
>

You realize that "various transformations" mean that the routable network
looks much different from the original OSM data. That make live updating
even harder.

A lot of programmers on this list have run into performance issues with
their routing implementations and now see "various transformations" as the
answer.

Few of them realize that they need to be mindful of cache misses. Accessing
data in L1 cache is 60 times faster than accessing main memory. Accessing
main memory sequentially is 30 times faster than accessing it in random
order.
http://www.elitebastards.com/index.php?option=com_content&id=705&Itemid=27&limitstart=3

Gosmore avoids "various transformations" and achieves perfectly adequate
performance by reducing cache misses. But there is certainly room for big
improvements.

-- 
Regards,
Nic
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