[Gretl-devel] Re: MPI and OpenMP (and openblas?)
Am 16.01.2020 um 12:40 schrieb Marcin Błażejowski:
On 16.01.2020 12:22, Sven Schreiber wrote:
> Hi, here's a question about what is really affected by setting the
> number of threads used by OpenMP via an environment variable and/or via
> the option to an MPI block (as explained in the gretl + MPI
> documentation).
By setting "--omp-threads=1" in MPI block you implicit define "set
omp_num_threads 1" in 'gretltmp-mpi.inp' script which is ran by all
gretlmpi executables.
Yes, that's what I thought.
But the fact is that in many cases some routines runs in parallel
via
OpenMP no matter what is the value of "omp_num_threads". I remember that
2-3 years ago Jack explained me that some algebra stuff lauch OpenMP
automagically.
Aha, that would explain it. But the question is, is it a bug? I mean if
we want to suppress multithreading, we want to do that also in the
openblas context, no?
thanks Marcin,
sven