[mpich-discuss] Can ch3:nemesis:mx use both MX and TCP networks ?

[Guillaume Mercier]

Hello Martin,

Audet, Martin a écrit :
>
> MPI_Users/MPI_Developers,
>
> 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 
> nodes).
>
When Nemesis:Mx is selected, only MX can be used.
>
> 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 possible).
>
Your interpretation is right.
>
> 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.

Guillaume