[mpich-discuss] problem with collective on sub-communicator

[Pavan Balaji]

The test code you sent seems to work fine for me. I don't see any such 
problem.

  -- Pavan

On 11/10/2011 03:14 PM, Miguel Oliveira wrote:
> Hi all,
>
> I wrote a very simple master/slave code in MPI and I'm having problems with MPI_Reduce, or even, MPI_Barrier, inside a subset of the world communicator.
> These operations don't seem to be waiting for all the processes in the subgroup.
>
> The code is a straightforward master/slave case where the master generates random numbers when requested and then retrieves a reduction of the sum of these
> done on the slaves.
>
> When run on more than three processes sometimes it happens that the message after the reduction, done from one of the slaves to inform the master of the final
> result gets to the master before some of the requests for random numbers... This ought to be impossible with a blocking reduction...
>
> Am I missing something?
>
> Code is attached.
>
> Help is appreciated.
>
> Cheers,
>
> MAO
>
>
>
>
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-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji