[Mpi-forum] C++ types inaccessible after #281

Jeff Hammond jhammond at alcf.anl.gov
Tue Jun 26 15:11:50 CDT 2012 

There is a huge difference between deprecating support for C++
_bindings_ and deprecating support for C++ _altogether_.  The ticket
is about the C++ bindings.  What Jed and I are trying to do is make
sure that the C _bindings_ allow users to work effectively within C++,
which means support std::complex<float/double/long double>.  Such
support already exists in MPI 2.2, but it requires changing "::" to
"_" so that one can use them with the C interface.

It is absolutely true that the Forum wants better C++ bindings and
will kill the original ones to make this happen.  However, you are the
first and only person who has suggested that the goal is to remove
support for C++ completely.  I believe that your statement "I thought
the point of 281 was to eradicate C++ from the standard" is completely
wrong and made with malice aforethought.  You're trying to rewrite
history to further your campaign to punish C++ programmers.

Many members of the Forum have made it clear that the goal is to
support C++ via the C bindings.  That does not mean eradicating C++
from the standard.  I assume that there will be text expressing the
Forum's believe that the C bindings are sufficient for C++, so clearly
there should be at least one mention of C++ in the standard.

As I said before, the right way to support C++ datatypes for the C
bindings is to restrict them to when a C++ compiler is used.  That
solves your issue with not having a C++ compiler.  I don't see why
you're arguing about the scenario when you don't have a C++ compiler.
Do you really have this use case as an implementer or are you just
making up silly arguments as part of your campaign of hate against
C++?

It is my understanding that your actions in regards to ticket #281 are
approved by IBM.  If this ticket is not supported by IBM, then it
would make me happy to hear this.

Jeff



On Tue, Jun 26, 2012 at 2:21 PM, Douglas Miller <dougmill at us.ibm.com> wrote:
>
> Jeff, This is inappropriate. Especially targeting IBM like that, and on a public mailing list. Ticket 281 has had plenty of discussions and passed votes. This is/was a Forum decision. The fact that I agreed with it, and volunteered to do a lot of the work, is why I am voicing my opinion on this.  We (the Forum) have said all along that anyone that has a better design for C++ bindings should bring that forward and make a proposal. Getting rid of the current, often considered "broken", C++ bindings is a good way to ensure any future proposal is free to change the design.
>
>
>
>
> _______________________________________________
> Douglas Miller                  BlueGene Messaging Development
> IBM Corp., Rochester, MN USA                     Bldg 030-2 A401
> dougmill at us.ibm.com               Douglas Miller/Rochester/IBM
>
> Jeff Hammond ---06/26/2012 02:09:59 PM---Jeff Hammond <jhammond at alcf.anl.gov>
>
> Jeff Hammond <jhammond at alcf.anl.gov>
> Sent by: mpi-forum-bounces at lists.mpi-forum.org
>
> 06/26/2012 01:57 PM
>
> Please respond to
> Main MPI Forum mailing list <mpi-forum at lists.mpi-forum.org>
>
>
> To
>
> Main MPI Forum mailing list <mpi-forum at lists.mpi-forum.org>,
>
>
> cc
>
>
> Subject
>
> Re: [Mpi-forum] C++ types inaccessible after #281
>
>
> Why do you want to make it so damn hard for anyone to use MPI in C++ codes?  You don't even have to do anything to support C++ because BG-MPI is based upon MPICH2.
>
> Can't we just for once try to take user needs into consideration instead of trying to reduce the workload of implementers as much as possible?
>
> Users matter.  In IBM land, they are called customers.  I assure you that some of your largest customers care a great deal about using MPI within C++.
>
> You're going out of your way to try and punish your customers for using C++.  Can't you just leave them alone?  Maybe we - the customers - need to leave IBM alone.
>
> Jeff
>
> On Tue, Jun 26, 2012 at 1:43 PM, Douglas Miller <dougmill at us.ibm.com> wrote:
>
> I think the issue is just that how can a standard that does not specify how C++ fits into things (after ticket 281) then go on to define a data type in terms of C++ types? If there is a need for a C (not C++) complex datatype, that should be a new proposal. But that datatype should not, in my opinion, be defined in terms of something like std::complex. If a platform does not support something like C99 complex types, then it will have to implement complex types and ops itself, or be incomplete.
>
>
>
>
> _______________________________________________
> Douglas Miller                  BlueGene Messaging Development
> IBM Corp., Rochester, MN USA                     Bldg 030-2 A401
> dougmill at us.ibm.com               Douglas Miller/Rochester/IBM
>
> Jeff Hammond ---06/26/2012 12:31:52 PM---Jeff Hammond <jhammond at alcf.anl.gov>
>
> Jeff Hammond <jhammond at alcf.anl.gov>
> Sent by: mpi-forum-bounces at lists.mpi-forum.org
>
> 06/26/2012 12:21 PM
>
>
>
> Please respond to
> Main MPI Forum mailing list <mpi-forum at lists.mpi-forum.org>
> To
>
> Main MPI Forum mailing list <mpi-forum at lists.mpi-forum.org>,
>
> cc
> Subject
>
> Re: [Mpi-forum] C++ types inaccessible after #281
>
>
> as far as i'm concerned, these types are only valid with the C bindings when a C++ compiler is used.  does that solve it?
>
> jeff
>
> On Tue, Jun 26, 2012 at 11:41 AM, Douglas Miller <dougmill at us.ibm.com> wrote:
>
> I've got to raise a concern here. If we start defining MPI datatypes to be C++ types then how will an implementation support that with only a C compiler? I thought the point of 281 was to eradicate C++ from the standard (and start over later if C++ was to be defined in the standard).
>
>
> _______________________________________________
> Douglas Miller                  BlueGene Messaging Development
> IBM Corp., Rochester, MN USA                     Bldg 030-2 A401
> dougmill at us.ibm.com               Douglas Miller/Rochester/IBM
>
> Jed Brown ---06/26/2012 11:26:16 AM---Jed Brown <jedbrown at mcs.anl.gov>
>
> Jed Brown <jedbrown at mcs.anl.gov>
> Sent by: mpi-forum-bounces at lists.mpi-forum.org
>
> 06/26/2012 11:14 AM
>
>
>
>
>
> Please respond to
>
> Main MPI Forum mailing list <mpi-forum at lists.mpi-forum.org>
> To
>
> Main MPI Forum mailing list <mpi-forum at lists.mpi-forum.org>,
>
> cc
> Subject
>
> Re: [Mpi-forum] C++ types inaccessible after #281
>
>
> On Tue, Jun 26, 2012 at 6:13 AM, Jeff Squyres <jsquyres at cisco.com> wrote:
>
> There are a few C++-specific datatypes for which it would be worth introducing new C datatypes (e.g., MPI_CXX_COMPLEX).  It's too bad that no one realized this until now, because this won't make the MPI-3 deadline.  But it could be part of MPI-3.1 or errata, or some such.
>
>
> Two people in offline discussions have suggested that C bindings to the std::complex types (I'm not aware of anything else that #281 will lose) might qualify as ticket 0._______________________________________________
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> --
> Jeff Hammond
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--
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond
https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond

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