Jeff
Thanks for your answers. I took careful notes.
Can I ask you another question???
I have old MPI code hardwired for 4 node computers.
If I define a couple of new "communicators" of
4 nodes each, can I run lots of 4 node runs
simultaneously by just replacing mpi_comm_world
with the new communicators?
e.g. mpirun -np 12 new_program
I can get 3 independent "4 node calculations"
from this command line by just changing
mpi_comm argument in the old MPI commands!!!
The real strength of communicators seems to be
to alter behavior of old MPI code by just changing
this one argument.
What command do you recommend to create the
new communicators?? mpi_comm_split?
I hope that made sense.
Chris
On Mon, Apr 07, 2003 at 10:05:20PM -0400, Jeff Squyres wrote:
> On Sat, 5 Apr 2003 seberino_at_[hidden] wrote:
>
> > It looks one can subdivide all nodes into groups. What is the purpose
> > then of having....
> >
> > mpi_comm_rank as well as mpi_group_rank???
> > mpi_comm_size as well as mpi_group_size???
>
> Groups are different than communicators in MPI. A communicator is a group
> with a unique context. Hence, you can have the same group in multiple
> communicators.
>
> > Are groups and comms interchangeable as arguments to mpi commands???
>
> No.
>
> > I thought they were equal but not I'm not sure.
>
> Check the MPI-1 standard, chapter 5.
>
> --
> {+} Jeff Squyres
> {+} jsquyres_at_[hidden]
> {+} http://www.lam-mpi.org/
> _______________________________________________
> This list is archived at http://www.lam-mpi.org/MailArchives/lam/
--
_______________________________________
Dr. Christian Seberino
SPAWAR Systems Center San Diego
Code 2872
49258 Mills Street, Room 158
San Diego, CA 92152-5385
U.S.A.
Phone: (619) 553-9973
Fax: (619) 553-6521
Email: seberino_at_[hidden]
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