[GRASS-dev] r.surf.contour inefficiency?

[Markus Metz]

Hamish wrote:
>
> Following r.cost @ 100%, I have changed cseg_open(16, 16, 8) to 256,256,64
> locally. 
FWIW, I found that r.watershed.seg is fastest with the equivalent of 
cseg_open(200, 200, <variable number of open segments>). It seems 
logical to use powers of 2, but 200, 200 is in r.watershed.seg faster 
than 128, 128 and 256, 256. 512, 512 is much slower again, there is a 
performance peak somewhere around 200, 200 for r.watershed.seg on my 
system. The segment library has strange dynamics, no idea what 
determines these dynamics, especially this performance peak.

Markus M