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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: 2012-04-09 19:04:29


Edgar,

I forgot to answer your previous question. I used MPI 1.5.4 and the C++ API.

Thatyene Ramos

On Mon, Apr 9, 2012 at 8:00 PM, Thatyene Louise Alves de Souza Ramos <
thatyene_at_[hidden]> wrote:

> Hi Edgar, sorry about the late response. I've been travelling without
> Internet access.
>
> Well, I took the code Rodrigo provided and modified the client to make the
> dup after the creation of the new inter communicator, without 1 process.
> That is, I just replaced the lines 54-55 in the *removeRank* method with
> my if-else block.
>
> I tried this because call a new create after the first create did not work
> and I thought it would might be the communicator . So, I tried to duplicate
> the inter communicator to see if worked.
>
> Thanks.
>
> Thatyene Ramos.
>
>
> On Thu, Apr 5, 2012 at 5:10 PM, Edgar Gabriel <gabriel_at_[hidden]> wrote:
>
>> so just to confirm, I ran our test suite for inter-communicator
>> collective operations and communicator duplication, and everything still
>> works. Specifically comm_dup on an intercommunicator is not
>> fundamentally broken, but worked for my tests.
>>
>> Having your code to see what your code precisely does would help me to
>> hunt the problem down, since I am otherwise not able to reproduce the
>> problem.
>>
>> Also, which version of Open MPI did you use?
>>
>> Thanks
>> Edgar
>>
>> On 4/4/2012 3:09 PM, Thatyene Louise Alves de Souza Ramos wrote:
>> > Hi Edgar, thank you for the response.
>> >
>> > Unfortunately, I've tried with and without this option. In both the
>> > result was the same... =(
>> >
>> > On Wed, Apr 4, 2012 at 5:04 PM, Edgar Gabriel <gabriel_at_[hidden]
>> > <mailto:gabriel_at_[hidden]>> wrote:
>> >
>> > did you try to start the program with the --mca coll ^inter switch
>> that
>> > I mentioned? Collective dup for intercommunicators should work, its
>> > probably again the bcast over a communicator of size 1 that is
>> causing
>> > the hang, and you could avoid it with the flag that I mentioned
>> above.
>> >
>> > Also, if you could attach your test code, that would help in hunting
>> > things down.
>> >
>> > Thanks
>> > Edgar
>> >
>> > On 4/4/2012 2:18 PM, Thatyene Louise Alves de Souza Ramos wrote:
>> > > 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]
>> > <mailto:gabriel_at_[hidden]>
>> > > <mailto:gabriel_at_[hidden] <mailto: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]> <mailto:
>> rsilva.oliveira_at_[hidden]
>> > <mailto:rsilva.oliveira_at_[hidden]>>
>> > > <mailto:rsilva.oliveira_at_[hidden]
>> > <mailto:rsilva.oliveira_at_[hidden]>
>> > > <mailto: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]>
>> > <mailto:gabriel_at_[hidden] <mailto:gabriel_at_[hidden]>>
>> > > > <mailto:gabriel_at_[hidden] <mailto:gabriel_at_[hidden]>
>> > <mailto: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] <mailto:users_at_[hidden]>
>> > <mailto:users_at_[hidden] <mailto:users_at_[hidden]>>
>> > > > http://www.open-mpi.org/mailman/listinfo.cgi/users
>> > >
>> > >
>> > > _______________________________________________
>> > > users mailing list
>> > > users_at_[hidden] <mailto:users_at_[hidden]>
>> > <mailto:users_at_[hidden] <mailto:users_at_[hidden]>>
>> > > http://www.open-mpi.org/mailman/listinfo.cgi/users
>> > >
>> > >
>> > >
>> > >
>> > > _______________________________________________
>> > > users mailing list
>> > > users_at_[hidden] <mailto:users_at_[hidden]>
>> > > http://www.open-mpi.org/mailman/listinfo.cgi/users
>> >
>> > --
>> > Edgar Gabriel
>> > Associate Professor
>> > Parallel Software Technologies Lab http://pstl.cs.uh.edu
>> > Department of Computer Science University of Houston
>> > Philip G. Hoffman Hall, Room 524 Houston, TX-77204, USA
>> > Tel: +1 (713) 743-3857 <tel:%2B1%20%28713%29%20743-3857>
>> > Fax: +1 (713) 743-3335 <tel:%2B1%20%28713%29%20743-3335>
>> >
>> >
>> > _______________________________________________
>> > users mailing list
>> > users_at_[hidden] <mailto:users_at_[hidden]>
>> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > users mailing list
>> > users_at_[hidden]
>> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>> --
>> Edgar Gabriel
>> Associate Professor
>> Parallel Software Technologies Lab http://pstl.cs.uh.edu
>> Department of Computer Science University of Houston
>> Philip G. Hoffman Hall, Room 524 Houston, TX-77204, USA
>> Tel: +1 (713) 743-3857 Fax: +1 (713) 743-3335
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>
>