[Gretl-devel] Re: MPI and OpenMP (and openblas?)
On Thu, 16 Jan 2020, Sven Schreiber wrote:
Am 16.01.2020 um 16:20 schrieb Allin Cottrell:
> On Thu, 16 Jan 2020, Sven Schreiber wrote:
>
> > OK, so given our recent discussion about the problems of openblas
> > multithreading, the ranking of the timings is maybe not so surprising
> > anymore. But: why does OMP_NUM_THREADS=1 have an additional effect over
> > --omp-threads=1 when everything happens inside the MPI block ?
> >
> > I hope the problem was clearly explained.
> Just about -- but there's one thing I need to know: when the script is
> taking a relatively long time, do you or don't you have
> OMP_NUM_THREADS=4 set in the environment?
>
Yes I do. Do you mean it takes precedence over the "inner" --omp-threads
setting?
I don't think so but I'm not sure. Just checked and on Linux, at any
rate, the --omp-threads setting wins.
Allin