This is with the 1.2 series, right?
Have you tried using what is described here:
http://www.open-mpi.org/faq/?category=openfabrics#v1.2-use-early-completion
I don't know if you can try OMPI v1.3 or not, but the issue described
in the the above FAQ item is fixed properly in the OMPI v1.3 series
(i.e., that MCA parameter is unnecessary because we fixed it a
different way).
FWIW, if adding an MPI_Barrier is the difference between hanging and
not hanging, it sounds like an Open MPI bug. You should never need to
add an MPI_Barrier to make an MPI program correct.
On Jan 23, 2009, at 8:09 AM, Gabriele Fatigati wrote:
Hi Igor,
My message size is 4096kb and i have 4 procs per core.
There isn't any difference using different algorithms..
2009/1/23 Igor Kozin <i.n.ko...@googlemail.com>:
what is your message size and the number of cores per node?
is there any difference using different algorithms?
2009/1/23 Gabriele Fatigati <g.fatig...@cineca.it>
Hi Jeff,
i would like to understand why, if i run over 512 procs or more, my
code stops over mpi collective, also with little send buffer. All
processors are locked into call, doing nothing. But, if i add
MPI_Barrier after MPI collective, it works! I run over Infiniband
net.
I know many people with this strange problem, i think there is a
strange interaction between Infiniband and OpenMPI that causes it.
2009/1/23 Jeff Squyres <jsquy...@cisco.com>:
On Jan 23, 2009, at 6:32 AM, Gabriele Fatigati wrote:
I've noted that OpenMPI has an asynchronous behaviour in the
collective
calls.
The processors, doesn't wait that other procs arrives in the call.
That is correct.
This behaviour sometimes can cause some problems with a lot of
processors in the jobs.
Can you describe what exactly you mean? The MPI spec specifically
allows
this behavior; OMPI made specific design choices and
optimizations to
support this behavior. FWIW, I'd be pretty surprised if any
optimized
MPI
implementation defaults to fully synchronous collective operations.
Is there an OpenMPI parameter to lock all process in the
collective
call until is finished? Otherwise i have to insert many
MPI_Barrier
in my code and it is very tedious and strange..
As you have notes, MPI_Barrier is the *only* collective operation
that
MPI
guarantees to have any synchronization properties (and it's a
fairly
weak
guarantee at that; no process will exit the barrier until every
process
has
entered the barrier -- but there's no guarantee that all
processes leave
the
barrier at the same time).
Why do you need your processes to exit collective operations at
the same
time?
--
Jeff Squyres
Cisco Systems
_______________________________________________
users mailing list
us...@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/users
--
Ing. Gabriele Fatigati
Parallel programmer
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it Tel: +39 051 6171722
g.fatigati [AT] cineca.it
_______________________________________________
users mailing list
us...@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/users
_______________________________________________
users mailing list
us...@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/users
--
Ing. Gabriele Fatigati
Parallel programmer
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it Tel: +39 051 6171722
g.fatigati [AT] cineca.it
_______________________________________________
users mailing list
us...@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/users
--
Jeff Squyres
Cisco Systems
