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

[Jed Brown]

MPI::COMPLEX is not the same as MPI_C_COMPLEX (and the latter is not
available on systems without C99).
On Jun 25, 2012 8:21 PM, "Fab Tillier" <ftillier at microsoft.com> wrote:

> Hi Jed,
>
> Maybe I'm not following you, but what predefined MPI datatype supports
> std::complex today?  My understanding is that there is no support for
> std::complex in MPI today, and that ticket 281 does not change this at all.
>
> Thanks,
> -Fab
>
> Jed Brown wrote on Mon, 25 Jun 2012 at 20:42:53
>
> > I see that std::complex will not be accessible in a predefined type if
> > #281 passes in its current form. Do you intend for there to be a
> > supported/recommended way for a C++ caller to get a complex predefined
> > (so that one-sided can be used) type? Note that C99 is not a subset of
> > any C++ and C99 complex cannot be used portably from C++ (even with
> > compiler suites that happen to support both).
>
> > On Jun 25, 2012 7:07 PM, "Fab Tillier" <ftillier at microsoft.com> wrote:
> > Hi Jed,
> >
> > Jed Brown wrote on Mon, 25 Jun 2012 at 16:43:54
> >
> >> Is it intended that #281 would make std::complex inaccessible? Should
> >> there be a MPI_CXX_COMPLEX, MPI_CXX_DOUBLE_COMPLEX,
> >> MPI_CXX_LONG_DOUBLE_COMPLEX, and (possibly) MPI_CXX_BOOL?
> >
> > I don't think ticket #281 does anything with respect to std::complex
> > accessibility.  The MPI standard defines the MPI_C_COMPLEX and family as
> > mapping to the C99 _Complex type (see Table 3.2, Predefined MPI
> > datatypes corresponding to C datatypes).  The standard is clear that
> > there are no corresponding C++ bindings.
> >
> >> Note that C99 complex is not a substitute because Microsoft does not
> >> implement it and it has different semantics regarding numerical
> >> stability. (Well, C99 semantics are specified and useful, std::complex
> >> stability is not specified by any C++ standard and in practice, is not
> >> implemented in a stable way.) This is not such a big deal for use with
> >> collectives because user-defined MPI_Ops can be used, but only
> >> predefined types can be used with one-sided operations, so presence of
> >> complex datatypes (or lack thereof) is relevant to applications.
> >
> > The fact that Microsoft does not support C99 is lame.  You can probably
> > get away using std::complex as a stand-in for C99 _Complex (but then
> > you're on your own), or move to a compiler that does (I believe the
> > Intel compiler supports C99 on Windows).
> >
> > -Fab
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mpi-forum.org/pipermail/mpi-forum/attachments/20120625/b4d99048/attachment-0001.html>