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Hi Jeff,
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<div class="">To be clear, C++ currently calls/uses the C99 interface for MPI (unless it uses the no-long-standard but possibly-still-present-in-libraries C++ bindings). That will still be true after these BigCount changes: C++ will see only the C99 symbols,
just like any other non-C11-compliant compiler. Polymorphism will not be supported in C++ because it cannot use C11 _Generic (because that is part of the C11 standard and is *not* part of the C++ standard). It also cannot use C++ overloading because are choosing
not to define any new C++ bindings in the MPI-4.0 standard. If libraries choose to supply C++ overloads, they may do so but they are not going to be part of the MPI-4.0 standard (they will have the same status as the Java bindings offered by Open MPI).<br class="">
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Cheers,</div>
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Dan.</div>
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—<br class="">
Dr Daniel Holmes PhD<br class="">
Architect (HPC Research)<br class="">
<a href="mailto:d.holmes@epcc.ed.ac.uk" class="">d.holmes@epcc.ed.ac.uk</a><br class="">
Phone: +44 (0) 131 651 3465<br class="">
Mobile: +44 (0) 7940 524 088<br class="">
Address: Room 2.09, Bayes Centre, 47 Potterrow, Central Area, Edinburgh, EH8 9BT</div>
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—</div>
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The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.</div>
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—</div>
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<div class="">On 31 Jul 2019, at 16:03, Jeff Squyres (jsquyres) via mpi-forum <<a href="mailto:mpi-forum@lists.mpi-forum.org" class="">mpi-forum@lists.mpi-forum.org</a>> wrote:</div>
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<div class="">On Jul 31, 2019, at 10:52 AM, Jeff Hammond <<a href="mailto:jeff.science@gmail.com" class="">jeff.science@gmail.com</a>> wrote:<br class="">
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You’re going to have to mention C++. You can’t just pretend that C++ supports C11 generic, because it explicitly doesn’t.<br class="">
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We are mentioning C++. Please re-read my prior email. <br class="">
<br class="">
<blockquote type="cite" class="">And you really should do this because it’s ridiculous not to use C++ polymorphism if we use C11’s.<br class="">
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There are three options:<br class="">
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1. Re-introduce C++ bindings, delay MPI-4.<br class="">
2. Re-introduce C++ bindings, BigCount misses the MPI-4 train.<br class="">
4. Do not re-introduce C++ bindings, BigCount catches the MPI-4 train.<br class="">
<br class="">
The feedback from the Forum was that BigCount was a blocker/gating issue for MPI-4. Hence, this is why the BigCount WG is not planning at this time to re-introduce C++ bindings via BigCount.<br class="">
<br class="">
There is a longer term plan (think: MPI-5) to introduce a full-featured set of C++ bindings to MPI -- one that does not necessarily have a 1:1 correspondence to the C bindings. That is a different, much longer effort, and will definitely not make it into MPI-4.<br class="">
<br class="">
-- <br class="">
Jeff Squyres<br class="">
<a href="mailto:jsquyres@cisco.com" class="">jsquyres@cisco.com</a><br class="">
<br class="">
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https://lists.mpi-forum.org/mailman/listinfo/mpi-forum<br class="">
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