[Routing] How to Establish Road Hierarchy

[Nic Roets]

Replying to David:
No, my application does not go to the cloud for long distances. But my
point is that it's often cheap to go to the cloud, if you can get a better
route there.

Yes, you can adapt A* in various ways. My own variation is to
stop considering residential roads that are far away from both the start
and finishing point. It's a simple way to get fast routing that is almost
always optimal. I disabled this heuristic precisely because of the point
I'm making, namely that processor time is pretty cheap compared to fuel,
man hours etc.

Lastly, you shouldn't take my comment about the 128GB RAM literally. Rather
read my whole email as a response to some of the things Dennis was saying.


On Wed, Dec 12, 2012 at 9:19 PM, David Piepgrass
<dpiepgrass at mentoreng.com>wrote:

> Wait, you’re saying you just go to the cloud for long-distance routes? But
> that’s no longer routing on a mobile device! Assuming your devices have
> laptop-like power is a bit of a cheat too, but I guess >50% of people
> probably have 1GHz+ by now... as for me I have to support a fleet of older
> devices with as little as 400MHz single-core and 48 MB RAM, and they are
> multifunction devices so I can’t use even half of that memory... so all my
> posts have come from that perspective.****
>
> ** **
>
> If you ask me, if it hogs too much memory and CPU for a Raspberry Pi, it’s
> not a real mobile solution. Just my opinion tho :) Processor speeds are
> stagnant, and slower devices will remain important as long as there is
> demand for low prices (so, as long as the third world exists). Non-cloud
> solutions will be important in some markets for the same reason. (and I
> always encourage people in the open-source community to think about the low
> end, since low-income people are major beneficiaries of OSS.)****
>
> ** **
>
> I'm talking about real life routing:****
>
> (A) In 2007 a mobile device typically had only 64MB RAM and a 300MHz
> processor. So, if you didn't have a routing hierarchy, it would take a
> minute or two to compute the average route a commuter would take. But now
> you have many phones and tablets with 1GB RAM and a 1GHz processor, so A*
> can buffer all the static data in RAM and only takes a few seconds.****
>
> (B) Furthermore, most devices are now Internet enabled and long routes can
> be calculated in the cloud using A*. I have demonstrated on many occasions
> that the longest routes in OpenStreetMap can be calculated fairly quickly
> on reasonable hardware e.g. only 30 seconds on a Xeon processor with 16 GB
> RAM. If a normal driver calculates all his routes with A*, the
> computational cost will be less than one hundredth of a cent per kilometre.
> Insignificant compared to the cost of fuel, man hours, mobile bandwidth etc.
> ****
>
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>
>


-- 
Regards,
Nic
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