[GRASS-user] Use of r.watershed

[hydro at hydromodeling.com]

Hello All,

I am new to GRASS but have been using GIS (mainly ESRI products) for  
quite a few years.  I am trying to learn how to use GRASS to carry out  
hydrology related analyses.  Currently, I am trying to use the  
r.watershed command to delineate the basins for a watershed.  My  
question is, how long would you expect it to take to run?  I am  
wondering if I am doing it wrong or if it just takes longer than I  
would expect.  The DEM is about 170MB TIFF before I import it to  
GRASS.  I have tried to run it a few times using different options,  
each time letting it run for 3 - 4 hours before killing it. I have  
tried both the -m and -4 flags.  Any input would be appreciated.