[mpich-discuss] A quick question on collective routines

[Darius Buntinas]

That just means that if one process calls mpi_bcast, then mpi_barrier, 
all processes in that communicator must call mpi_bcast before mpi_barrier.

-d

On 01/08/2010 04:36 PM, Hiatt, Dave M wrote:
> I need to know if I've made a really dumb mistake.  The implications are big;
>
> On a collective routine, like MPI:: Bcast, when it is broadcast out, do the compute nodes that read in the data have to always respond in the exact order (the ordering being rank) each time.  That is, if the first message is read by nodes 1,3,5,7,9,2,4,6,8,10 in that order, to all subsequent broadcasts on the same communicator for the lives of those processes have to occur in the same order.
>
> I'm trying to make sense of the following sentence is "Using MPI".  "MPI requires that collective routines on the same communicator be called by all processes in that communicator , in the same order".
>
> Thanks a whole lot for help
>
> dave
>
>
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