[mpich-discuss] nonblocking collectives, progress thread

[Jeff Hammond]

One way to implement nonblocking allreduce would be to use
MPI_Accumulate, so it doesn't seem entirely nuts.  I presume you know
the MPICH2 implementation of MPIX_Iallreduce does not use RMA...

Jeff

On Fri, Apr 6, 2012 at 6:24 PM, Rajeev Thakur <thakur at mcs.anl.gov> wrote:
> You mean your program doesn't call MPI_Win_create and MPI_win_free but Jumpshot shows them? No, that's not normal.
>
> Rajeev
>
> On Apr 6, 2012, at 3:14 PM, Pieter Ghysels wrote:
>
>> Dear,
>>
>> I'm replacing calls to MPI_Allreduce by calls to MPIX_Iallreduce.
>> I'm compiling with -mpe=mpilog and look at the communication pattern
>> with jumpshot. The MPI_Allreduce's are gone now of course, but
>> mpe/jumpshot does not show MPIX_Iallreduce. Instead, where the
>> MPI_Allreduce used to be, now a lot of time is being spent in
>> MPI_Win_create and MPI_Win_free, where before the MPI_Allreduce was
>> taking place. Is this normal?
>>
>> Can I configure MPICH2 to use a progress thread for the nonblocking
>> collectives, as in libNBC?
>> Do I have to use MPI_Init_thread()?
>>
>> Pieter
>>
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-- 
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
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