[mkgmap-dev] [PATCH v1] - Reduce number of Table A entries required

Tue Sep 22 07:43:55 BST 2009

Hi Mark,

On Tue, Sep 22, 2009 at 12:49:17AM +0100, Mark Burton wrote:
> 
> Reduce number of Table A entries.
>     
>     Previously, Table A entries were unique for each combination of start node,
>     end node and RoadDef. But no information from the start and end nodes goes
>     into Table A so we can ignore the start and end nodes and all roads
>     within a given routing centre that use the same RoadDef can now share a
>     Table A entry. This reduces the number of entries required which makes
>     the .img files smaller and, hopefully, also improves the routing because
>     routing centres can now cover a larger area.
> 
> I have tested this with mapsource and on a Nuvi and it appears to work
> OK but it really needs more testing before it could be considered for
> committing.

I successfully tested it on Finland with Edge 705 firmware 2.90.  The map
is slightly smaller (36 megabytes instead of 37) and routing (car and bicycle,
200 to 250 km distance) still works.  It still makes a stupid detour for
the bicycle route, but I would blame that on the Garminware.

> So, all feedback is welcome regarding the effect this patch has on
> routing performance. With the patch, the routing changed and I thought
> it was more sensible but perhaps that's just wishful thinking.

It could be that the bicycle route calculation was faster with this patch,
but then again, there were not that many streets to choose from in my test.
Calculation of bicycling routes through cities has always been slowest
(multiple minutes).

	Marko