[mpiwg-sessions] Fwd: WPM Session Handle

Joseph Schuchart schuchart at icl.utk.edu
Wed Dec 1 09:26:23 CST 2021

Ping. Any opinions/inputs on this?


-------- Forwarded Message --------
Subject: 	WPM Session Handle
Date: 	Sun, 31 Oct 2021 11:08:06 -0400
From: 	Joseph Schuchart <schuchart at icl.utk.edu>
To: 	mpiwg-sessions <mpiwg-sessions at lists.mpi-forum.org>

Hi all,

The Hybrid-WG is currently discussing the Continuations proposal. Part 
of that proposal is a new continuation request type that is not bound to 
any communication operation, and thus not connected to any communicator, 
window, or file. That floating state is somewhat disatisfying. We are 
thus considering connecting it to a session, i.e., provide a session 
handle at creation. This would potentially allow us to isolate the 
execution of continuations from different sessions. Unfortunately, this 
is not possible at the moment because there is no default session handle 
for the WPM model.

 From my (arguably uninformed outside) point of view, the WPM is a 
special type of session worthy of its own handle (MPI_SESSION_WPM, for 
example), which can be used with all functions expecting session handles 
as input. As an example, `MPI_Session_get_info(MPI_SESSION_WPM)` would 
return an info object containing the "thread_level" info key and the 
value passed to MPI_Init_thread (or "single" for MPI_Init). I'm sure 
there are other more hairy procedures, but you get the point.

Has this been discussed before? Was there a good reason not to have a 
WPM session handle? If not, can we add something like MPI_SESSION_WPM to 
allow future API extensions to use session handles?


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