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Re: What happened to short float?

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On Thu, 8 Feb 2018 11:27:51 -0800 (PST)
jameskuyper@verizon.net wrote:

> I don't agree. Based upon 5.2.4.2.2p11,12,13, and 16, here's a
> comparison of the requirements for C float and double with the actual
> characteristics of IEEE single and double precision formats:
> 
> Feature     |float|  IEEE single  |double|      IEEE double
> ================================================================
> _EPSILON    |1E-5 |   0X1P-23F    | 1E-9 |        0X1P-52
> _DECIMAL_DIG|  6  |       9       |  10  |          17
> _DIG        |  6  |       6       |  10  |          15
> _MIN        |1E-37|   0X1P-126F   | 1E-37|       0X1P-1022
> _TRUE_MIN   |1E-37|   0X1P-149F   | 1E-37|       0X1P-1074
> _MIN_10_EXP | -37 |      -37      |  -37 |         -307
> _MAX        |1E37 |0X1.fffffeP127F| 1E37 |0X1.fffffffffffffP1023
> _MAX_10_EXP | 37  |       38      |  37  |          308
> 
> The requirements of the standard appear to have been targeted to a
> base 10 implementation. Allowing for that fact, the limits on the MIN
> and MAX values for float and double (which are identical) are pretty
> close to IEEE single precision. However, the minimum values for the
> precision- related characteristics are different for float and
> double, and significantly lower than actual values for the
> corresponding IEEE formats.

Clearly, you're right! I was a bit distracted by the binary definitions
from the IEEE 754 standard.

Obviously the collective defined limits for the float, double and long
double type doesn't work for an half_t type covering the IEEE 754
binary16 format.

Since the exponent width of the binary16 format is 5 bits corresponding
to the range [-14, +15] with a 15 exponent bias, it could be safe to
define an half_t type with HLF_MIN equal to 1E-4 and HLF_MAX equal to
1E+4. This range should be enought to cover a normalized value in
[0.0, 1.0] corresponding to the [0, 1023] range for a 10-bit color
component.

-- 
GOTHIER Nathan

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What happened to short float? Philipp Klaus Krause <pkk@spth.de> - 2018-01-17 17:21 +0100
  Re: What happened to short float? "James R. Kuyper" <jameskuyper@verizon.net> - 2018-01-17 11:42 -0500
    Re: What happened to short float? jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-02 23:08 +0100
      Re: What happened to short float? Jakob Bohm <jb-usenet@wisemo.com> - 2018-02-05 07:57 +0100
        Re: What happened to short float? jameskuyper@verizon.net - 2018-02-05 05:31 -0800
      Re: What happened to short float? Tim Prince <tprince@intelretiree.com> - 2018-02-05 08:55 -0500
        Re: What happened to short float? jacobnavia <jacob@jacob.remcomp.fr> - 2018-02-05 15:46 +0100
        Re: What happened to short float? GOTHIER Nathan <nathan.gothier@gmail.com> - 2018-02-08 01:29 +0100
          Re: What happened to short float? Keith Thompson <kst-u@mib.org> - 2018-02-07 16:59 -0800
            Re: What happened to short float? Philipp Klaus Krause <pkk@spth.de> - 2018-02-08 09:08 +0100
              Re: What happened to short float? Keith Thompson <kst-u@mib.org> - 2018-02-08 09:27 -0800
            Re: What happened to short float? GOTHIER Nathan <nathan.gothier@gmail.com> - 2018-02-08 09:54 +0100
              Re: What happened to short float? Keith Thompson <kst-u@mib.org> - 2018-02-08 10:13 -0800
            Re: What happened to short float? jameskuyper@verizon.net - 2018-02-08 06:36 -0800
              Re: What happened to short float? GOTHIER Nathan <nathan.gothier@gmail.com> - 2018-02-08 17:04 +0100
                Re: What happened to short float? jameskuyper@verizon.net - 2018-02-08 08:56 -0800
                Re: What happened to short float? scott@slp53.sl.home (Scott Lurndal) - 2018-02-08 17:23 +0000
                Re: What happened to short float? GOTHIER Nathan <nathan.gothier@gmail.com> - 2018-02-08 18:52 +0100
                Re: What happened to short float? jameskuyper@verizon.net - 2018-02-08 11:27 -0800
                Re: What happened to short float? GOTHIER Nathan <nathan.gothier@gmail.com> - 2018-02-08 22:58 +0100
              Re: What happened to short float? Keith Thompson <kst-u@mib.org> - 2018-02-08 10:18 -0800
          Re: What happened to short float? Jakob Bohm <jb-usenet@wisemo.com> - 2018-02-08 18:59 +0100
            Re: What happened to short float? Robert Wessel <robertwessel2@yahoo.com> - 2018-02-08 16:22 -0600
              Re: What happened to short float? Jakob Bohm <jb-usenet@wisemo.com> - 2018-02-09 15:01 +0100
  Re: What happened to short float? Chad <cdalten@gmail.com> - 2018-01-17 09:12 -0800
  Re: What happened to short float? scott@slp53.sl.home (Scott Lurndal) - 2018-01-17 17:31 +0000
  Re: What happened to short float? jacobnavia <jacob@jacob.remcomp.fr> - 2018-01-17 19:52 +0100
    Re: What happened to short float? Philipp Klaus Krause <pkk@spth.de> - 2018-01-18 13:18 +0100
      Re: What happened to short float? bartc <bc@freeuk.com> - 2018-01-18 12:40 +0000

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