[MPICH] MPI_Probe, MPI_Iprobe MPI_Bcast

[Thomas Moschny]

Eng. A.A. Isola wrote:
> Question:
>
> Is it possible to use the MPI_Probe or MPI_Iprobe in order 
> to check if there's a message received by MPI_Bcast?
>   
No, because MPI_Bcast is a collective operation. All members of the
communicator used there must call MPI_Bcast simultaneously. MPI_Bcast
behaves like a barrier. So if one of the members doesn't call MPI_Bcast,
you'll have a deadlock.

Additionally, collective and p2p messages don't mix, so the MPI_Iprobe
(p2p) will not tell you that you have to call MPI_Bcast (collective) now
to receive something.

Thomas