[Users] parallel program

[Erik Schnetter]

On Dec 5, 2006, at 08:10:43, Jan Hegewald wrote:

> Hello,
>
> Am 04.12.2006 um 17:13 schrieb David Rideout:
>
>> The cactus executable is just an executable which uses mpi.  It
>> depends on your site, but a common way to start it is e.g.
>>
>> mpirun -np 16 cactus_my_config my_par_file.par
>>
>> Is this your question?
>
> yes. Thank you very much for making this clear. I thought cactus
> might have an own mechanism to launch distributed programmes.
> So the same limitations which apply to raw mpi programmes also apply
> to cactus applications (e.g. seldom possible to run with different
> mpi implementations on different machines)?

If you didn't find this in the users' guide, then we need to add it.   
Thanks for the pointer.

There are MPI versions that you can use across very different  
machines, such as MPICH (I think) or MPICH-G2, built on Globus.  That  
is, instead of making different MPI versions interact, you would  
build the interoperability into MPI itself.

The reason for this is probably that our simulations are mostly  
tightly coupled simulations, and we currently don't change the number  
of participating processors once a run has started.  However, this is  
not a restriction of Cactus itself, it is mostly a restriction of the  
drivers we use.  (A driver is a thorn that provides the large,  
parallel 3D arrays that we use to solve our PDE's.)  Different  
drivers which use different data structures could very naturally add  
or remove processors at run time.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>

My email is as private as my paper mail.  I therefore support encrypting
and signing email messages.  Get my PGP key from www.keyserver.net.



-------------- next part --------------
A non-text attachment was scrubbed...
Name: PGP.sig
Type: application/pgp-signature
Size: 186 bytes
Desc: This is a digitally signed message part
Url : http://www.cactuscode.org/pipermail/users/attachments/20061205/df8f945a/attachment.bin