[mpich-discuss] Can ch3:nemesis:mx use both MX and TCP networks ?
atchley at myri.com
Tue Oct 13 12:10:36 CDT 2009
On Oct 13, 2009, at 1:05 PM, Guillaume Mercier wrote:
>> I always thought (but never tested) that the ch3:nemesis:mx
>> cmehannel has the ability to independently select either MX or TCP
>> to communicate between any pair of MPI processes when shared memory
>> communication isn’t possible (e.g. the two process run on different
> When Nemesis:Mx is selected, only MX can be used.
Not only it is a runtime selection, but it is a compile time selection.
You could compile your application against a shared MPICH2 Nemesis/TCP
lib. You could then run that binary and use LD_LIBRARY_PATH to select
either a Nem/TCP or a Nem/MX libmpich.so.
>> However after carefully reading the README file, I fear mpich2
>> doesn’t have this flexibility that is, network communication with
>> the ch3:nemesis:mx channel is always done using MX (of course
>> network communication occurs when shared memory communication isn’t
> Your interpretation is right.
Guillaume, does Nemesis handle shmem directly or does it pass it to
Nem/MX to let MX handle the shmem?
>> When shared memory communication isn’t possible, does the
>> ch3:nemesis:mx channel has the ability to independently select
>> either MX or TCP to communicate between two MPI processes ?
> The Mx module does not offer this kind of possibility. Could you
> explain to me when shared memory is not possible within
> a node ? I don't see the case.
I believe he is asking for selection of Nem/TCP or Nem/MX for non-
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