I agree with Jeff that this is a non-issue. Bill’s assertion that adding Fortran support for large count once you have C support has been true in MPICH development at least and no vender would drop anything just to put MPI 4.0 compatibility on a marketing slide. They’d just put it on the slide anyway. Every implementation out there has some sort of exception, intentional or otherwise, that makes them technically non-compliant. In the end, their users determine 1) whether they care enough to request the feature and 2) whether they care enough to switch to a competing library.
I think the best way forward is to do something like what had been proposed when the embiggening/pythonization started and separate bindings from specification and just say that an MPI implementation has MPI 4.0 C bindings and MPI 3.1 F08 bindings and MPI 5.0 Python bindings. That means each binding can be updated in whatever way makes sense for them. For 4.0, I don’t think this is an issue that needs to be resolved. Us telling the implementations what they have to do will have essentially no impact anyway. Thanks, Wes > On Jan 11, 2021, at 6:26 AM, Rolf Rabenseifner via mpi-forum > <mpi-forum@lists.mpi-forum.org> wrote: > > Dear Jeff and all, > >> I think their users would be very unhappy. > > Yes, users can be unhappy and compute centers may definitely recommend > an other MPI library - at least for any software development. > > I want to remember that MPI-3.1 requires for the mpi module: > > "Provide explicit interfaces according to the Fortran routine interface speci > cations. > This module therefore guarantees compile-time argument checking and allows > positional > and keyword-based argument lists. If an implementation is paired with a > compiler that either does not support TYPE(*), DIMENSION(..) from TS 29113, or > is otherwise unable to ignore the types of choice buffers, then the > implementation must > provide explicit interfaces only for MPI routines with no choice buer > arguments. See > Section 17.1.6 for more details." > > Although there are no more such compilers that do not provide one of the two > methods, > there are more than 5 years after MPI-3.1 still MPI libraries that do not > provide keyword-based argument lists with the mpi module. > And those libraries provide such support for the mpi_f08 module. > This means, they prove that they are not MPI-3.1 compliant :-) > > > Sometimes implementors ignore the goals and the wording of the MPI standard. > > > And there is also no request that users want to have a less-quality > mpi module definition. > > Best regards > Rolf > > > ----- Original Message ----- >> From: "Main MPI Forum mailing list" <mpi-forum@lists.mpi-forum.org> >> To: "Main MPI Forum mailing list" <mpi-forum@lists.mpi-forum.org> >> Cc: "Jeff Squyres" <jsquy...@cisco.com> >> Sent: Sunday, January 10, 2021 5:09:55 PM >> Subject: Re: [Mpi-forum] Big Fortran hole in MPI-4.0 Embiggening > >> I can't imagine a vendor would: >> >> - support mpi_f08 >> - then stop supporting mpi_f08 just so that they can get an "MPI-4.0" release >> out >> - then support mpi_f08 again >> >> I think their users would be very unhappy. >> >> >> >> >> >> On Jan 10, 2021, at 10:55 AM, William Gropp via mpi-forum < [ >> mailto:mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> >> | mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> ] > >> wrote: >> >> I agree with Dan that this is a big change from the RCM. Further, the >> approach >> in MPI has always been to encourage the users to make it clear to the vendors >> what is acceptable in implementations, especially implementation schedules. >> Nothing in the standard prohibits implementors from continuing to provide MPI >> 3.x implementations while they work to provide a full MPI 4.0 implementation. >> The MPI forum has no enforcement power on the implementors, and I believe >> this >> text is unnecessary and will not provide the guarantee that Rolf wants. >> Further, frankly once the C embiggened interface is implemented, creating the >> mpi_f08 version is relatively straightforward. >> >> Bill >> >> William Gropp >> Director, NCSA >> Thomas M. Siebel Chair in Computer Science >> University of Illinois Urbana-Champaign >> IEEE-CS President-Elect >> >> >> >> >> >> >> On Jan 10, 2021, at 7:44 AM, HOLMES Daniel via mpi-forum < [ >> mailto:mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> >> | mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> ] > >> wrote: >> >> Hi Rolf, >> >> This is a (somewhat contrived, arguably) reason for taking another tiny step >> towards removing the “mpif.h” method of Fortran support and pushing users and >> implementations towards preferring the Fortran 2008 interface, which is a >> direction of travel that I fully support. >> >> I think this might be seen as quite a big change for implementers, >> especially if >> it were to occur between the RCM and FRM. >> >> Cheers, >> Dan. >> — >> Dr Daniel Holmes PhD >> Architect (HPC Research) >> [ mailto:d.hol...@epcc.ed.ac.uk <mailto:d.hol...@epcc.ed.ac.uk> | >> d.hol...@epcc.ed.ac.uk <mailto:d.hol...@epcc.ed.ac.uk> ] >> Phone: +44 (0) 131 651 3465 >> Mobile: +44 (0) 7940 524 088 >> Address: Room 2.09, Bayes Centre, 47 Potterrow, Central Area, Edinburgh, EH8 >> 9BT >> — >> The University of Edinburgh is a charitable body, registered in Scotland, >> with >> registration number SC005336. >> — >> >> >> >> >> On 10 Jan 2021, at 12:22, Rolf Rabenseifner via mpi-forum < [ >> mailto:mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> >> | mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> ] > >> wrote: >> >> This email was sent to you by someone outside the University. >> You should only click on links or attachments if you are certain that the >> email >> is genuine and the content is safe. >> >> Dear MPI-Forum members, >> >> MPI-3.1 and MPI-4.0 includes the following rule on top of the 2nd page >> of the Language Binding chapter: >> >> | MPI implementations providing a Fortran interface must provide >> | one or both of the following: >> | - The USE mpi_f08 Fortran support method. >> | - The USE mpi and INCLUDE 'mpif.h' Fortran support methods. >> >> The embiggening was included only in the C and mpi_f08 bindings. >> >> Most implementors nowadays provide all three MPI Fortran support methods, >> i.e., the mpi_f08 and the mpi module and mpif.h. >> >> For all MPI-3.1 libraries that provide all three MPI Fortran support methods, >> the most easiest and fastest way to provide MPI-4.0 for C and Fortran is, >> - to implement the embiggening for C, >> - and to remove the mpi_f08 module, >> - and maybe months or years later, to provide mpi_f08 again, now embiggened. >> >> This implementation path (by removing mpi_f08 from MPI-3.1 and to name >> it MPI-4.0 without Fortran embiggening) was of course never intended, >> when we decided to require the embiggened routines only for mpi_f08. >> The goal was >> - to not require additional work from the implementors for the old mpi module >> - convince the users that it is a good idea to make a transition >> to mpi_f08. >> >> The most simplest way to resolve this problem would be to require >> mpi_f08 for MPI-4.0, i.e., to change the text to >> >> | MPI implementations providing a Fortran interface >> | - must provide the USE mpi_f08 Fortran support method, >> | - and additionally may provide both, >> | the USE mpi and INCLUDE 'mpif.h' Fortran support methods. >> >> What is your opinion? >> >> I expect that we should discuss this next Wednesday at our MPI Forum telcon. >> >> Best regards >> Rolf >> >> -- >> Dr. Rolf Rabenseifner . . . . . . . . . .. [ mailto:rabenseif...@hlrs.de >> <mailto:rabenseif...@hlrs.de> | email >> rabenseif...@hlrs.de <mailto:rabenseif...@hlrs.de> ] . >> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 . >> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 . >> Head of Dpmt Parallel Computing . . . [ >> https://urldefense.com/v3/__http://www.hlrs.de/people/rabenseifner__;!!DZ3fjg!pq7EsFbFnneGZo_3EudtIahAxSmoQr0t9AbsAl3CqBoVuMfHl3ICDYnCimsJIa6Siw$ >> >> <https://urldefense.com/v3/__http://www.hlrs.de/people/rabenseifner__;!!DZ3fjg!pq7EsFbFnneGZo_3EudtIahAxSmoQr0t9AbsAl3CqBoVuMfHl3ICDYnCimsJIa6Siw$> >> | www.hlrs.de/people/rabenseifner <http://www.hlrs.de/people/rabenseifner> ] >> . >> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . 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(Office: Room 1.307) . > _______________________________________________ > mpi-forum mailing list > mpi-forum@lists.mpi-forum.org <mailto:mpi-forum@lists.mpi-forum.org> > https://lists.mpi-forum.org/mailman/listinfo/mpi-forum > <https://lists.mpi-forum.org/mailman/listinfo/mpi-forum>
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