<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Howard,<div class=""><br class=""></div><div class="">My initial impression (from reading your email but not looking at the PDF yet), is:</div><div class="">* I much prefer Rolf’s suggested reference to generic/unspecified “collective operations” rather than nailing it down to MPI_Ialltoall.</div><div class="">* I don’t like the restriction that the user must finalise sessions in a particular order to match the internal implementation of a single session finalise at some remote process (e.g. the scenario of Rolf’s case A on issue 435).</div><div class=""><br class=""></div><div class="">More fundamental: we need a decision tree to tease apart the design decisions we are making at pace and with no reference implementation.</div><div class=""><br class=""></div><div class="">First choice: does MPI_SESSION_FINALISE do anything non-local? If so, what?</div><div class="">If no, then next choice is: </div><div class=""><br class=""></div><div class="">Root Q1: Do we wish to mandate that the user must do clean up prior to MPI_SESSION_FINALISE? If so, then eek! Breach of rule of least astonishment.</div><div class="">Branch Q2: If no, then do we wish to mandate that MPI_SESSION_FINALISE does whatever clean up has not been done by the user? If so, eek! Significant change to accepted text.</div><div class=""><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Branch Q3: If no, then does MPI_SESSION_FINALISE do anything non-local? If so, eek! What does it do? Panic.</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Branch Q4: If no, then does MPI_SESSION_FINALISE need to be defined as collective? If so, eek! Why? Why does it need that semantic? Panic.</div><div class="">Branch Q5: If no, <span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">then does MPI_SESSION_FINALISE need to be defined as non-local? If so, eek! Why? Why does it need that semantic? Panic.</span></div><div class=""><div class="">Branch Q6: If no, <span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">then we should define MPI_SESSION_FINALISE as local (meaning weak-local, of course)? If so, strike all text about collective operation(s) of any kind and strike any restriction on ordering of calls and strike any restriction on the permitted associations/derivations of communicators from sessions.</span></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br class=""></span></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">This is a linear decision tree that leads to:</span></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br class=""></span></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">"</span></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">MPI_SESSION_FINALIZE is a local procedure; it does not free MPI objects derived from the session. It is erroneous to use MPI objects derived from a session after calling MPI_SESSION_FINALIZE for that session.</span></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br class=""></span></div><div class=""><font color="#000000" class=""><span style="caret-color: rgb(0, 0, 0);" class="">If the user wishes to recover resources from MPI objects derived from a session, then appropriate calls to MPI procedures must be made by the user prior to calling MPI_SESSION_FINALIZE, such as MPI_COMM_DISCONNECT (from communicators), MPI_WIN_FREE (for windows), and MPI_FILE_CLOSE (for files).</span></font></div><div class=""><font color="#000000" class=""><span style="caret-color: rgb(0, 0, 0);" class="">“</span></font></div><div class=""><font color="#000000" class=""><span style="caret-color: rgb(0, 0, 0);" class=""><br class=""></span></font></div><div class=""><font color="#000000" class=""><span style="caret-color: rgb(0, 0, 0);" class="">Discuss.</span></font></div><div class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""></div></div></div><div class="">
<meta charset="UTF-8" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class="Apple-interchange-newline">Cheers,</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">Dan.</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">—</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">Dr Daniel Holmes PhD</div>Executive Director<br class="">Chief Technology Officer<br class=""><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">CHI Ltd</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><a href="mailto:danholmes@chi.scot" class="">danholmes@chi.scot</a></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br class=""></div></div><br class="Apple-interchange-newline">
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<div><br class=""><blockquote type="cite" class=""><div class="">On 19 Feb 2021, at 18:13, Pritchard Jr., Howard via mpiwg-sessions <<a href="mailto:mpiwg-sessions@lists.mpi-forum.org" class="">mpiwg-sessions@lists.mpi-forum.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta charset="UTF-8" class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">HI All,<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">Ah this is exciting. So I spent some time on baking verbiage to add about MPI_Session_finalize<span class="Apple-converted-space"> </span><i class="">non-local</i><span class="Apple-converted-space"> </span>behavior.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">See the attached cutout from the results pdf.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">I’ve added verbiage describing the semantics (copying some wording from MPI_Sendrecv, or at least the flavor) of session finalize in the event that the user has not cleaned up MPI objects associated with the session(s).<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">It’s a simple easy to understand (I think) model. Basically session finalize has the semantics of a MPI_Ialltoall for each communicators still associated with the session at finalize, followed by a waitall. As long as all other processes finalizing their sessions generate in aggregate, a message pattern which matches, no deadlock. If not, potential deadlock. One takeaway from this is that we can’t support arbitrary associations of communicators to sessions in each MPI process when the app doesn’t do its own cleanup so as to make MPI_Session_finalize a local op.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">I’ve added some examples and we can add more as we think needed. May have to change the presentation mechanism however.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">I didn’t want to open this as a PR at this point, hence this notification mechanism.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">Howard<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">-- <o:p class=""></o:p></span></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 10.5pt;" class="">Howard Pritchard<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 10.5pt;" class="">HPC-ENV<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 10.5pt;" class="">Los Alamos National Laboratory<o:p class=""></o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><span id="cid:44A8CC70700025488E1FC53700367736@win.lanl.gov"><temp.pdf></span><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">_______________________________________________</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; 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