[GE users] New MPICH2 Howto online

reuti reuti at staff.uni-marburg.de
Thu Nov 27 11:28:08 GMT 2008


Hi Ionel,

Am 27.11.2008 um 11:31 schrieb igardais:

> Hi Reuti,
>
> Thanks for your work, I'm in the process to test with IntelMPI.
>
> I have a bit-off-topic question about MPI and version dependency  
> (please forgive if it looks obvious. I don't want to start a troll  
> thread).
> Why are mpi-compiled programs so tightly linked to the version of  
> MPI used ?

the MPI standard is an API (application programming interface), not  
an ABI (application binary interface). It's from time to time on the  
Beowulf or MPICH and Open MPI lists http://www.open-mpi.org/community/ 
lists/devel/2008/09/4634.php to have an ABI.

Different MPI implementations need different enviroment variables and  
different daemons (or none). There is simply no standard defined,  
e.g. for MPI_Comm_rank() how it has to be implemented, so that you  
could switch the library used for it at runtime. Or the format of the  
machinefile: every MPI implementations wants to offer different  
features and need sometimes a different formatting for it (e.g. using  
forks in MPICH(1) with the "node01:2" syntax instead of repeated rsh/ 
ssh/qrsh calls with a simple list of host (needs even recompilation  
of MPICH(1) with -comm=shared configured), or Open MPI with "node01  
slots=2", using a different interface than the primary one in MPICH 
(2) "node01:2 ifhn=node01-grid".

> For instance, whatever mpi startup method is used, it is done  
> outside the code. So how could it impact the generated binaries ?
> Beside the startup method issue, a call to 'MPI_Comm_rank 
> (MPI_COMM_WORLD, &rank)' looks the same whether you use mpich, openmp

Open MPI you meant - OpenMP is a different standard.

-- Reuti


> or lam/mpi.
> Is there an ongoing effort to unify this, enabling mpi programs to  
> switch between libraries tranparently (at least for the common  
> basic calls) ?
>
> Thanks,
> Ionel
>
>
>
> reuti wrote:
>> Hi,
>>
>> an updated MPICH2 Howto is available now including the mpd startup
>> method and an adjusted daemon based smpd startup method. It's
>> available on the Howto page http://gridengine.sunsource.net/howto/
>> howto.html.
>>
>> I left out any hint about Intel MPI compatibility until it's
>> confirmed or disproved. For now: just try and let me know.
>>
>> -- Reuti
>>
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