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

Douglas Miller dougmill at us.ibm.com
Tue Jun 26 14:21:44 CDT 2012


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                                                  
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                                       Re: [Mpi-forum] C++ types           
             06/26/2012 01:57          inaccessible after #281             
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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.





  _______________________________________________
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  IBM Corp., Rochester, MN USA                     Bldg 030-2 A401
  dougmill at us.ibm.com               Douglas Miller/Rochester/IBM

  Inactive hide details for Jeff Hammond ---06/26/2012 12:31:52 PM---Jeff
  Hammond <jhammond at alcf.anl.gov>Jeff Hammond ---06/26/2012 12:31:52
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       Jeff Hammond <                                                      
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                                                      Re: [Mpi-forum] C++  
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  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

        Inactive hide details for Jed Brown ---06/26/2012 11:26:16 AM---Jed
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        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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University of Chicago Computation Institute
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