> On Nov 21, 2017, at 8:53 AM, r...@open-mpi.org wrote:
>
>> On Nov 21, 2017, at 5:34 AM, Noam Bernstein <noam.bernst...@nrl.navy.mil
>> <mailto:noam.bernst...@nrl.navy.mil>> wrote:
>>
>>>
>>> On Nov 20, 2017, at 7:02 PM, r...@open-mpi.org <mailto: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.
I can now confirm that "—map-by numa:PE=2" does indeed work, and seems to give
good performance.
thanks,
Noam
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