[mvapich-discuss] Fwd: Completion of non-blocking collective MPI_Iallgather

[Hari Subramoni]

Hello Pramod,

Apologies about the delay. We are looking into this and will get back to
you shortly.

Regards,
Hari.

On Tue, Jan 27, 2015 at 9:45 AM, pramod kumbhar <pramod.s.kumbhar at gmail.com>
wrote:

> Could someone provide any suggestion on this?
>
> Thanks.
>
> ---------- Forwarded message ----------
> From: Kumbhar Pramod Shivaji <pramod.kumbhar at epfl.ch>
> Date: Mon, Jan 26, 2015 at 6:02 PM
> Subject: [mvapich-discuss] Completion of non-blocking collective
> MPI_Iallgather
> To: "mvapich-discuss at cse.ohio-state.edu" <
> mvapich-discuss at cse.ohio-state.edu>
>
>
>  Hello All,
>
>  I am looking into mpi non-blocking collectives (specifically
> mpi_iallgather & mpi_iallgatherv)
> and wondering about the internal completion / progress of these routines.
> To explain, I have following
> pseudo example:
>
>  MPI_Iallgather(…&req)        *  // this called by all ranks at the same
> time*
> ...
> while( i < 4) {
>
>            compute(…);   // compute for few seconds
>           MPI_Test(…&flag, &req);                               *   //
> Can I expect this flag to be true? i.e. operation is completed here at some
> point?*
>           i++;
> }
> ….
> MPI_Wait(&req);   * // I see that MPI_Iallgather is getting finished when
> everyone calls MPI_Wait at this point, why?*
>
>
>  I was running this test example on single node with 8 mpi ranks. I see
> that MPI_Test is always returning false. With
> compute() function of two seconds, I expect MPI_Iallgather to finish
> quickly. But instead mpi_iallgather is completed
> at MPI_Wait(). See attached sample trace of the program.
>
>  Could anyone point out possible cause of this behaviour? It will be
> great help.
>
>
>  Regards,
> Pramod
>
>  MVAPICH 2 version: 2.0
> Configure command:  /configure --with-slurm
>  --with-slurm-include=slurm/default/include
> --with-slurm-lib=slurm/default/lib  --with-pm=none --with-pmi=slurm
> --enable-threads=multiple --enable-shared --enable-sharedlibs=gcc
> --enable-fc --enable-cxx --with-mpe --enable-rdma-cm --enable-fast
> --enable-smpcoll --with-hwloc --enable-xrc --with-device=ch3:mrail
> --with-rdma=gen2 --enable-cuda --with-cuda=/usr/local/cuda-5.0
> --with-cuda-include=/usr/local/cuda-5.0/include
> --with-cuda-lib=/usr/local/cuda-5.0/lib64 --enable-g=dbg --enable-debuginfo
> CC=gcc CXX=g++ FC=gfortran F77=gfortran
>
>
>
>
> _______________________________________________
> mvapich-discuss mailing list
> mvapich-discuss at cse.ohio-state.edu
> http://mailman.cse.ohio-state.edu/mailman/listinfo/mvapich-discuss
>
>
>
> _______________________________________________
> mvapich-discuss mailing list
> mvapich-discuss at cse.ohio-state.edu
> http://mailman.cse.ohio-state.edu/mailman/listinfo/mvapich-discuss
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.cse.ohio-state.edu/pipermail/mvapich-discuss/attachments/20150127/0653d8b6/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: mpi_iallgather_trace.png
Type: image/png
Size: 79473 bytes
Desc: not available
URL: <http://mailman.cse.ohio-state.edu/pipermail/mvapich-discuss/attachments/20150127/0653d8b6/attachment-0001.png>