[Difx-users] Machines file using mpich

[Adam Deller]

Hi Ajay,

I'm not aware of a way to control the number of threads on a per-process
basis in mpich.  You can (and should) set the phread worker processes
spawned by each Core process in the .threads file.  The first entry in the
.threads file corresponds to the first Core process, the second to the
second Core process, and so on.  Those are the only significant consumers
of CPU, and you would normally set that number to 1 fewer than the number
of CPU cores you have available (so that last core is available to do the
sending and receiving etc).  Actually there are two other threads running
on the Core process (one doing only communication, one doing the small
amount of other non-communication housekeeping that is needed) but they can
happily co-exist on a single CPU core.

For the FxManager and Datastream processes, there's no way to limit the
number of CPU cores they use, but they are not very compute intensive
except in special corner cases anyway.

Cheers,
Adam

On 11 June 2018 at 14:37, Gill, Ajaypal <ajaypal.gill at cfa.harvard.edu>
wrote:

> Hi,
>
> I understand that when using openmpi, it's possible for instance to set
> the .machines file as follows to select the number of cores to use per node:
>
> node1 slots=10 #fx manager
>
> node2 slots=10 #datastream1
>
> node3 slots=10 #datastream2
>
> node4 slots=10 #datastream3
>
> node5 slots=20 #core
>
> However, I see that this format doesn't work when using mpich. Is there
> any similar way to select the number of cores per node using mpich?
>
> Best regards,
>
> Ajay Gill (summer student)
>
>
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-- 
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Dr. Adam Deller
ARC Future Fellow, Senior Lecturer
Centre for Astrophysics & Supercomputing
Swinburne University of Technology
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phone: +61 3 9214 5307
fax: +61 3 9214 8797

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