> On Nov 20, 2017, at 7:02 PM, r...@open-mpi.org wrote:
>
> So there are two options here that will work and hopefully provide you with
> the desired pattern:
>
> * if you want the procs to go in different NUMA regions:
> $ mpirun --map-by numa:PE=2 --report-bindings -n 2 /bin/true
> [rhc001:131460] MCW rank 0 bound to socket 0[core 0[hwt 0-1]], socket 0[core
> 1[hwt 0-1]]:
> [BB/BB/../../../../../../../../../..][../../../../../../../../../../../..]
> [rhc001:131460] MCW rank 1 bound to socket 1[core 12[hwt 0-1]], socket 1[core
> 13[hwt 0-1]]:
> [../../../../../../../../../../../..][BB/BB/../../../../../../../../../..]
>
> * if you want the procs to go in the same NUMA region:
> $ mpirun --map-by ppr:2:numa:PE=2 --report-bindings -n 2 /bin/true
> [rhc001:131559] MCW rank 0 bound to socket 0[core 0[hwt 0-1]], socket 0[core
> 1[hwt 0-1]]:
> [BB/BB/../../../../../../../../../..][../../../../../../../../../../../..]
> [rhc001:131559] MCW rank 1 bound to socket 0[core 2[hwt 0-1]], socket 0[core
> 3[hwt 0-1]]:
> [../../BB/BB/../../../../../../../..][../../../../../../../../../../../..]
>
> Reason: the level you are mapping by (e.g., NUMA) must have enough cores in
> it to meet your PE=N directive. If you map by core, then there is only one
> core in that object.
Makes sense. I’ll try that. However, if I understand your explanation
correctly the docs should probably be changed, because they seem to be
suggesting something that will never work. In fact, would the ":PE=N" > 1
ever work for "—map-by core”? I guess maybe if you have hyperthreading on, but
I’d still argue that that’s an unhelpful example, given how rarely
hyperthreading is used in HPC.
Noam
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|U.S. NAVAL|
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LABORATORY
Noam Bernstein, Ph.D.
Center for Materials Physics and Technology
U.S. Naval Research Laboratory
T +1 202 404 8628 F +1 202 404 7546
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