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

Scott Atchley atchley at myri.com
Tue Oct 13 16:36:37 CDT 2009

On Oct 13, 2009, at 2:18 PM, Dave Goodell 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 nodes).
>>> 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.
> That would work, but it's a bit heavyweight.  I believe that  
> switching between TCP or MX at runtime is currently possible via an  
> environment variable as documented here: http://wiki.mcs.anl.gov/mpich2/index.php/Nemesis_Runtime_Netmod_Selection
> Skimming the doc it looks like some of the names are a bit stale (s/ 
> newtcp,gm/tcp,mx/g), but the basic idea should still hold and the  
> environment variable definitely still has the same name.  I'll take  
> a quick pass over that doc soon.


Interesting, I did not know this existed. I had not run across it in  
the README or the manual.



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