[mpiwg-p2p] FP16 Support

[Jeff Hammond]

Note that I'm only referring to IEEE storage format. We should not require
compliance with IEEE floating-point arithmetic in reduction operators,
although it's obviously nice if implementations provide it.

Jeff

On Wed, Jun 21, 2017 at 10:40 PM Jeff Hammond <jeff.science at gmail.com>
wrote:

> I would like to move beyond languages here and have MPI define IEEE754
> types. So we'd have e.g. MPI_IEEE32BIT for single, etc.
>
> MPI would do the math according to IEEE in whatever language the
> implementation uses. Languages would need to have a compatible type to
> allow the user to manipulate the resulting buffers.
>
> Jeff
>
> Sent from my iPhone
>
> > On Jun 21, 2017, at 10:24 PM, Atsushi HORI <ahori at riken.jp> wrote:
> >
> > Hello, Bill,
> >
> >> 2017/06/22 14:03、William Gropp <wgropp at illinois.edu> wrote;
> >>
> >> On timing, note that MPI already defined optional types.  One of these
> is MPI_REAL2, which is a 2-byte floating point type - that is, FP16. (See
> p25, line 36, 177, line 2, 540 line 10, and 674 line 38).  Was MPI_REAL2
> discussed?
> >
> > I did not notice of that and there was no discussion about MPI_REAL2
> (unless I missed).
> >
> > I checked 3.1 standard as you pointed out, but MPI_REAL2 is defined as a
> Fortran type. I believe that there is no C predefined type for FP16 (or
> 'MPI_HALF') in MPI 3.1. This is just because ISO C does not define FP16 yet.
> >
> >
> > — from p25, MPI 3.1,
> > MPI requires support of these datatypes, which match the basic datatypes
> of Fortran and ISO C. Additional MPI datatypes should be provided if the
> host language has additional data types: MPI_DOUBLE_COMPLEX for double
> precision complex in Fortran declared to be of type DOUBLE COMPLEX;
> MPI_REAL2, MPI_REAL4, and MPI_REAL8 for Fortran reals, declared to be of
> type REAL*2, REAL*4 and REAL*8, respectively; MPI_INTEGER1, MPI_INTEGER2,
> and MPI_INTEGER4 for Fortran integers, declared to be of type INTEGER*1,
> INTEGER*2, and INTEGER*4, respectively; etc.
> >
> > -----
> > Atsushi HORI
> > ahori at riken.jp
> > http://aics-sys.riken.jp
> >
> >
> >
> >
> > _______________________________________________
> > mpiwg-p2p mailing list
> > mpiwg-p2p at lists.mpi-forum.org
> > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-p2p
>
-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mpi-forum.org/pipermail/mpiwg-p2p/attachments/20170622/31f874ce/attachment.html>