On Thu, Dec 15, 2016 at 10:29 AM, Guillaume Mercier < [email protected]> wrote:

Hi Jeff,

On 15/12/2016 18:48, Jeff Hammond wrote:

...

The number of output communicators from MPI_Comm_split(_type) is always one.

Yes, obviously.

Different ranks may get different outputs, but one cannot transfer

...

a communicator object from one rank to another.

That's my issue actually.

If you want to do how many total output communicators there are, you can

...

perform an MPI_Allgather on the color arguments and see how many unique values there are.

I'm not sure about that: tae the case of MPI_Comm_split_type with MPI_COMM_TYPE_SHARED. According to tha standards :"this type splits the communicator into subcommunicators each of which can create a shared memory region". So, there is only one color, but several subcommunicators. Or am I understanding this the wrong way?

Each rank gets its own subcommunicator object that captures the ranks of the shared memory domain, as supported by MPI_Win_allocate_shared. I'm still not sure I understand what the issue is. What are you trying to do? Jeff

Regards Guillaume

_______________________________________________ mpi-forum mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpi-forum

-- Jeff Hammond [email protected] http://jeffhammond.github.io/