[Gretl-devel] Re: MPI and OpenMP (and openblas?)
Am 16.01.2020 um 22:18 schrieb Allin Cottrell:
On Thu, 16 Jan 2020, Sven Schreiber wrote:
> Am 16.01.2020 um 19:50 schrieb Sven Schreiber:
> The slowdowns of the previous message with Allin's script
(e.g.
> --omp-threads=2 and OMP_NUM_THREADS=2) were much more drastic, however.
I can't replicate those slowdowns on Linux (for each --omp-threads
case, times are invariant with respect to the OMP_NUM_THREADS setting)
but I'll try on Windows tomorrow.
I'm seeing this on another machine as well, timings going from roughly
2.5s to 8.5s when OMP_NUM_THREADS=1 is changed to OMP_NUM_THREADS=2 (and
--omp-threads=2). This was still the Jan-11th snapshot.
Then I have upgraded to the latest snapshot of "just now". There I don't
see a noticeable difference anymore - but that's because both variants
are now slow!
Like this:
GRETL_OLD_SVD is 1
OMP_NUM_THREADS is 1
--omp-threads option is 2
Entering MPI real-time read loop
gretlmpi 2020a-git
Aktuelle Sitzung: 2020-01-16 23:08
k = 40, elapsed: 8.36354s
k = 40, elapsed: 8.50609s
Hm..
sven