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

Jed Brown jedbrown at mcs.anl.gov
Tue Jun 26 15:08:10 CDT 2012

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:
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