[fitsbits] 16-bit floats {External}

[Bob Garwood]

H for half-precision floats?



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-------- Original message --------
From: peter teuben via fitsbits <fitsbits at listmgr.nrao.edu>
Date: 7/23/25 9:25 AM (GMT-05:00)
To: fitsbits at listmgr.nrao.edu
Cc: peter teuben <teuben at umd.edu>
Subject: Re: [fitsbits] 16-bit floats {External}

We also need them for BINTABLE, where D and E are for 64 and 32 bit
floats.  Sadly can't expand the alphabet here. F is available, but C is not.

  I guess L is available for 128-bit integer.


FITS format code Description                     8-bit bytes

L                        logical (Boolean)               1
X                        bit                             *
B                        Unsigned byte                   1
I                        16-bit integer                  2
J                        32-bit integer                  4
K                        64-bit integer                  8
A                        character                       1
E                        single precision float (32-bit) 4
D                        double precision float (64-bit) 8
C                        single precision complex        8
M                        double precision complex        16
P                        array descriptor                8
Q                        array descriptor                16

On 7/23/25 08:34, Thomas Robitaille via fitsbits wrote:
> Hi everyone,
>
> As far as I understand, IEEE 754-2008 standardized the representation
> of 16-bit floats (as well as 128-bit floats). I was curious whether
> there is any interest in extending the FITS format to allow BITPIX=-16
> and BITPIX=-128?
>
> I am aware of some modern projects that would benefit from having
> 16-bit floats, since they consider it to be sufficient in precision to
> store very large datasets, and using 16-bit floats would perform a lot
> better than using compression on 32-bit floats for example, and 16-bit
> floats would allow a larger dynamic range than using 16-bit ints with
> BSCALE/BZERO.
>
> I'm curious to hear if this has been discussed before!
>
> Thanks,
> Tom
>
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> fitsbits at listmgr.nrao.edu
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