[mpich-discuss] MPICH2 (or MPI_Init) limitation | scalability

[Dave Goodell]

On Jan 10, 2012, at 7:20 AM, Bernard Chambon wrote:

> Le 10 janv. 2012 à 00:52, Dave Goodell a écrit :
>
>> Make sure you include a call to MPI_Finalize in your test program  
>> as well.
>>
>> -Dave
>
>
> I'm afraid that not the problem
>
> The question is that there is a limitation in mpich2 software or  
> more probably in my OS|Machine, but I can't find it ?
> there is clearly a limit at 152 tasks even after getting rid of  
> limits (*),  and increasing shared memory values (**)
[snip]
> >sysctl -A | grep kernel.sh
> kernel.shmmni = 16000
> kernel.shmall = 8388608000
> kernel.shmmax = 33554432


This number (shmmax) looks to be too low to me.  It's only 32 MiB,  
which is pretty small.  Try increasing this by a factor of 8 or so and  
see if you end up fixing your problem.

How many processes are you launching on each node?

-Dave