MPI_ROOT is required for the rooted operations of the inter-communicator
collectives in MPI-2, I am not aware of that you need MPI_ROOT in
intra-communicator collectives as defined in MPI-1.
Michael Kluskens wrote:
> The constant MPI_ROOT is not universally defined in all current
> shipping MPI implementations.
> Is there any MPI function/call that requires MPI_ROOT?
> From the complete reference it appears that MPI_ALLGATHER might be
> the one routine.
> This all relates to portability, code I write using OpenMPI has to
> work on other systems not using OpenMPI.
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