[GRASS-dev] Fwd: [GRASS-user] Re: grass-user Digest, Vol 30, Issue 22

[Markus Metz]

Markus Neteler wrote:
> On Thu, Oct 9, 2008 at 11:13 PM, Michael Barton <michael.barton at asu.edu> wrote:
>   
>> Below is a recent exchange between Markus (Neteler) and me about the new
>> r.watershed.fast.
>> The gist is the question: is it ready to go into the develbranch_6 and trunk
>> (7) svn or does it need more testing. I thought it was already in the main
>> svn, but Markus pointed out that it is still in Addons.
>>     
>
> Indeed it is not even in Addons - I tried to point out that Addons would be
> a good place to facilitate testing.
>
> @Markus: if you are interested, please check here:
> http://trac.osgeo.org/grass/wiki/HowToContribute#WriteaccesstotheGRASS-Addons-SVNrepository
> -> Write access to the GRASS-Addons-SVN repository
>   
Yes, I am interested! And this new version might need some testing, in
particular for the seg mode. The original version uses very little
memory, so assuming that GRASS runs today on systems where at least
500MB RAM are available I changed the parameters for the seg mode, more
data are kept in memory, speeding up the seg mode. Looking at other
modules using the segment library (e.g. v.surf.contour, r.cost), it
seems that there is not one universally used setting, instead the
segment parameters are tuned to each module. The new settings work for
me, but not necessarily for others, and maybe using 500MB is a bit much.
Still, the seg mode is slow and testing would require a lot of patience.
I only tested it for smaller regions, not yet for regions that would
require several GB of RAM. The aim is to get close to 2,147,483,647
cells in a region... BTW, has anybody recently used the seg mode of the
original version successfully and done so because the non-segmented
r.watershed would run out of memory?

I'm rather confident about the ram version, but it can do only good if
developers review the new code.

Will try to get write access to the GRASS-Addons-SVN repository, and add
an entry in the GRASS-Addons wiki.

Thanks for your feedback!

Markus