[MPIWG Fortran] FP16 16-bit-floating-point

[Rolf Rabenseifner]

(Because I'm not member of j3, only Reinhold's or Rich's answers will be visible for j3)

Based on Reinhold's answer, I make my questions more precise:

- Are there already some activities in J3 on this FP16 topic?

- When will the Fortran standard include REAL16 to support the new IEEE FP16 standard? 

Best regards
Rolf


----- Original Message -----
> From: "Reinhold Bader" <Reinhold.Bader at lrz.de>
> To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>, "fortran standards email list for J3" <j3 at j3-fortran.org>
> Cc: "MPI-WG Fortran working group" <mpiwg-fortran at lists.mpi-forum.org>, "Atsushi Hori" <ahori at riken.jp>, "Martin Schulz"
> <schulzm at llnl.gov>, "MPI WG Point To Point Communications working group" <mpiwg-p2p at lists.mpi-forum.org>
> Sent: Friday, June 16, 2017 2:31:03 PM
> Subject: AW: FP16 16-bit-floating-point

> Hello Rolf,
> 
> to the best of my knowledge, the answers are as follows:
> 
> Q1: Not in the sense of having an explicit name like the REAL32, REAL64, REAL128
> names for specific integer kinds that were added to Fortran 2008.
>        However, it is left free to implementors to create a new kind number in the
>        implementation that could be returned by SELECTED_REAL_KIND() and,
>         if IEEE conforming, by IEEE_SELECTED_REAL_KIND() and consequently all relevant
>         IEEE support routines.
> 
> Q2: REAL*2 is (like REAL*8) a non-conforming notation (REAL*8 is supported as an
> extension by many implementations), so the answer is no.
>        A proper declaration might look like
> 
>        integer, parameter :: rk = selected_real_kind(2,6)    ! at least 2 decimal
>        digits and 6 maximal decimal exponent - hope I have this right ...
>        real(KIND=rk) :: x
> 
>       with the following caveats:
>      * the KIND that fits the requirement most closely will be used, so it might be
>      necessary to use the STORAGE_SIZE intrinsic to check what one gets.
>      * KIND numbers are non-portable, so might vary for one and the same kind between
>      implementations (at least one compiler I know deviates from all others I know).
> 
> I checked three of the compilers I know: they currently do not support FP16.
> 
> Regards
> Reinhold
> 
> 
>> -----Ursprüngliche Nachricht-----
>> Von: Rolf Rabenseifner [mailto:rabenseifner at hlrs.de]
>> Gesendet: Freitag, 16. Juni 2017 13:53
>> An: fortran standards email list for J3 <j3 at j3-fortran.org>; Bader, Reinhold
>> <Reinhold.Bader at lrz.de>
>> Cc: MPI-WG Fortran working group <mpiwg-fortran at lists.mpi-forum.org>;
>> Atsushi Hori <ahori at riken.jp>; Martin Schulz <schulzm at llnl.gov>; MPI WG
>> Point To Point Communications working group <mpiwg-p2p at lists.mpi-
>> forum.org>
>> Betreff: FP16 16-bit-floating-point
>> 
>> Hi all together,
>> 
>> I'm sitting in the MPI Forum Meeting and we discuss the new IEEE FP16
>> datatype.
>> 
>> Questions to the Fortran atandardization body:
>> 
>> - Does the Fortran Standardization Body has already a proposal for
>>   the new name in Fortran for this IEEE FP16?
>> 
>> - Will be REAL*2 identical to IEEE FP16?
>> 
>> Best regards
>> Rolf
>> 
>> --
>> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de .
>> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .
>> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .
>> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner .
> > Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .

-- 
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de .
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner .
Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .