[GRASS-user] r.watershed.fast new version

[Markus Metz]

Hi all,

some time ago I posted a new version of r.watershed with substantial
speed increase, but still with slight differences in the outputs
compared to the original version. This problem is solved, whether or not
these differences in flow direction and flow accumulation were critical.
Now the results in flow direction and flow accumulation are 100%
identical to the original version. All other outputs are based on flow
direction and flow accumulation and therefore also identical.

The speed increase for the ram version is the same as with my first
version: e.g. a region with 22,500,000 cells is processed in 1minute 6
seconds, the original version needs 10 hours. The modified seg version
(-m flag set) needs 16 minutes (North Carolina sample data, elevation
resampled to 3 m). No idea how long the original seg version needs for
such a region, more than a day I guess.

The source code of r.watershed.fast available here
http://markus.metz.giswork.googlepages.com/r.watershed_fast_version.tar.gz

If you give this modified version a try, please let me know if it works
or not, I tested it only on Linux 32bit and Linux 64bit.

Markus