Remi,
in the same environment, can you
mpirun -np 1 grep Cpus_allowed_list /proc/self/status
it is likely Open MPI allows only one core, and in this case, i suspect
MKL refuses to do some time sharing and hence transparently reduce the
number of threads to 1.
/* unless it *does* time sharing, and you observed 4 threads with the
performance of one */
mpirun --bind-to none ...
will tell Open MPI *not* to bind on one core, and that should help a bit.
note this is suboptimal, you should really ask mpirun to allocate 4
cores per task, but i cannot remember the correct command line for that
Cheers,
Gilles
On 6/22/2016 4:17 PM, remi marchal wrote:
Dear openmpi users,
Today, I faced a strange problem.
I am compiling a quantum chemistry software (CASTEP-16) using intel16,
mkl threaded libraries and openmpi-18.1.
The compilation works fine.
When I ask for MKL_NUM_THREAD=4 and call the program in serial mode
(without mpirun), it works perfectly and use 4 threads.
However, when I start the program with mpirun, even with 1 mpi
process, the program ran but only with 1 thread.
I never add such kind of trouble.
Does anyone have an explanation.
Regards,
Rémi
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