As I read it, the standard implies it is a local operation. That said, this could be inefficient with resources. MPI_Init() implies that other processes are possibly initializing at the same time, and so they can find better ways to share node and cluster resources. For example, Instant On might be faster with MPI_Init(). Michael A. Raymond HPE HPC Development Environment 1 (612) 851-0500

On Jan 4, 2023, at 12:32, Pritchard Jr., Howard via mpiwg-sessions <[email protected]> wrote:

Hi All,

First, Happy New Year!

I’ve got a question about the semantics of MPI_Session_init. In particular, I’d be interested in knowing people’s opinion on whether this function is nonlocal or local. We don’t have any text in the current version of the standard that states whether or not MPI_Session_init is a nonlocal operation.

I’m considering options for handling this issue: https://github.com/open-mpi/ompi/issues/11166 . It turns out that the way to properly resolve this issue depends on whether or not MPI_Session_init has local or nonlocal semantics.

I had been working under the assumption that we had intended session initialization to be a local function, but considering how to resolve issue 11166 made me begin to question this assumption.

Thanks for any ideas,

Howard

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<image001.png> Howard Pritchard Research Scientist HPC-ENV

Los Alamos National Laboratory [email protected]

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