[Mpi-forum] "BigCount" rendering in PDF

Jeff Hammond jeff.science at gmail.com
Wed Jul 31 10:59:31 CDT 2019

It’s a long email to read on my phone while on vacation. 

You just need a sentence that says C++ compilers support C bindings, including the C11 generic stuff, just using a very different mechanism. Is that going to delay MPI-4?

In any case, all the issues with polymorphism is exactly why it’s so important to have explicit symbols for C89/C99 usage so that implementations can add extensions that do the polymorphism stuff if it doesn’t get voted in. If you don’t say C++, there’s no reason OMPI and MPICH can’t do the obvious, trivial and intelligent thing.


Sent from my iPhone

> On Jul 31, 2019, at 8:03 AM, Jeff Squyres (jsquyres) <jsquyres at cisco.com> wrote:
>> On Jul 31, 2019, at 10:52 AM, Jeff Hammond <jeff.science at gmail.com> wrote:
>> You’re going to have to mention C++. You can’t just pretend that C++ supports C11 generic, because it explicitly doesn’t.
> We are mentioning C++.  Please re-read my prior email.  
>> And you really should do this because it’s ridiculous not to use C++ polymorphism if we use C11’s.
> There are three options:
> 1. Re-introduce C++ bindings, delay MPI-4.
> 2. Re-introduce C++ bindings, BigCount misses the MPI-4 train.
> 4. Do not re-introduce C++ bindings, BigCount catches the MPI-4 train.
> 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.
> 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.
> -- 
> Jeff Squyres
> jsquyres at cisco.com

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