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

Tue Jun 26 15:44:24 CDT 2012

Sure, that sounds pretty reasonable. I just wanted to ask whether it seemed
strange to have "std::complex" in there. Seems like (slightly) more than
"ticket-0" to me, but should be a simple proposal to write.

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                                       Re: [Mpi-forum] C++ types           
             06/26/2012 03:08          inaccessible after #281             
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On Tue, Jun 26, 2012 at 10:43 AM, 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?

Is there an informal expectation that implementations will continue to
provide an mpicxx wrapper?

I see no reason for anyone to be attached to std::complex (actually, I
think it's very frequently a bad choice), but having *some* way to use
complex types with a predefined (because one-sided cripples non-predefined)
MPI_Op still seems important.

  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.

As mentioned earlier, implementations making MPI_C_COMPLEX available
independent of C99 would be sufficient. Otherwise we are stuck defining our
own types for complex, and then can't use one-sided.

Some discussion of work-arounds:
http://trac.mcs.anl.gov/projects/mpich2/ticket/1525
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