[GRASS-user] r.resamp.* and CPU usage

[Blumentrath, Stefan]

Hi Markus,

Thanks for the reply.
> When you use time, 100% of CPU means one core is fully used. Two fully used cores would be reported by time as 200%. Both modules use only a 
> single core. 

I started r.reamp.bspline and r.resamp.rst once and saw equally many PIDs in htop than cores in the system and all cores got ~ 80% busy.
At the same time I got an email from a colleague asking me if I could spare some CPU for him as well, because his processes got significantly slowed down ;-)

> lib/gmath used by r.resamp bspline might use more cores if GRASS has been compiled with openmp, but for r.resamp.bspline you would
> only see a marginal increase in CPU usage above 100%.
I compiled GRASS 7.0 with OpenMP option, yes.

> Only very few GRASS modules can use more than one core. For openmp, you can control the number of cores with
> setenv OMP_NUM_THREADS X

export OMP_NUM_THREADS=5 solved it for me on Ubuntu.

Thanks again!

Kind regards,
Stefan