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Subject: Re: [OMPI users] Problem with MPI_Barrier (Inter-communicator)
From: Thatyene Louise Alves de Souza Ramos (thatyene_at_[hidden])
Date: 2012-04-04 15:18:25


Hi there.

I've made some tests related to the problem reported by Rodrigo. And I
think, I'd rather be wrong, that *collective calls like Create and Dup do
not work with Inter communicators. I've try this in the client group:*

*MPI::Intercomm tmp_inter_comm;*
*
*
*tmp_inter_comm = server_comm.Create (server_comm.Get_group().Excl(1,
&rank));*
*
*
*if(server_comm.Get_rank() != rank)*
* server_comm = tmp_inter_comm.Dup();*
*else*
* server_comm = MPI::COMM_NULL;*
*
*
The server_comm is the original inter communicator with the server group.

I've noticed that the program hangs in the Dup call. It seems that the
tmp_inter_comm created without one process still has this process, because
the other processes are waiting for it call the Dup too.

What do you think?

On Wed, Mar 28, 2012 at 6:03 PM, Edgar Gabriel <gabriel_at_[hidden]> wrote:

> it just uses a different algorithm which avoids the bcast on a
> communicator of 1 (which is causing the problem here).
>
> Thanks
> Edgar
>
> On 3/28/2012 12:08 PM, Rodrigo Oliveira wrote:
> > Hi Edgar,
> >
> > I tested the execution of my code using the option -mca coll ^inter as
> > you suggested and the program worked fine, even when I use 1 server
> > instance.
> >
> > What is the modification caused by this parameter? I did not find an
> > explanation about the utilization of the module coll inter.
> >
> > Thanks a lot for your attention and for the solution.
> >
> > Best regards,
> >
> > Rodrigo Oliveira
> >
> > On Tue, Mar 27, 2012 at 1:10 PM, Rodrigo Oliveira
> > <rsilva.oliveira_at_[hidden] <mailto:rsilva.oliveira_at_[hidden]>> wrote:
> >
> >
> > Hi Edgar.
> >
> > Thanks for the response. I just did not understand why the Barrier
> > works before I remove one of the client processes.
> >
> > I tryed it with 1 server and 3 clients and it worked properly. After
> > I removed 1 of the clients, it stops working. So, the removal is
> > affecting the functionality of Barrier, I guess.
> >
> > Anyone has an idea?
> >
> >
> > On Mon, Mar 26, 2012 at 12:34 PM, Edgar Gabriel <gabriel_at_[hidden]
> > <mailto:gabriel_at_[hidden]>> wrote:
> >
> > I do not recall on what the agreement was on how to treat the
> size=1
> >
> >
> >
> >
> >
> > _______________________________________________
> > users mailing list
> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
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