Using OpenMPI 4.0.1 and no configuration files of any kind on a linux
machine which shows 4 CPUS and 2 threads per CPU. When this is run:
mpirun --allow-run-as-root --oversubscribe -np 3
/usr/common/modules/el8/x86_64/software/q6/6.0.1-CentOS-vanilla/bin/qdynp
eq2.inp
it works and the expected 3
Hello David,
The slot calculation is based on physical cores rather than logical cores. The
4 CPUs you are seeing there are logical CPUs. And since your processor has 2
threads per core, you have two physical cores; yielding a total of 4 logical
cores (which is reported to lscpu). On machine
Note that you can also resolve it by adding --use-hwthread-cpus to your cmd
line - it instructs mpirun to treat the HWTs as independent cpus so you would
have 4 slots in this case.
> On Jun 8, 2020, at 11:28 AM, Collin Strassburger via users
> wrote:
>
> Hello David,
>
> The slot calculatio
So default
slots = "CPU"s/2
but there is some leeway in what is considered to be a CPU? So far I
have not found the actual formula documented anywhere.
Thanks,
David Mathog
On Mon, Jun 8, 2020 at 11:37 AM Ralph Castain via users
wrote:
>
> Note that you can also resolve it by adding --use-h
The default number of slots is the number of physical cores; overall, this
tends to yield the best performance.
Most of the time, a "CPU" is a logical core. A processor with hyper-threading
(or SMT (simultaneous multi-threading)) will be counted as two(+) logical
processors.
I hope this helps
