Re: routine for angles needed

From	James Kuyper <jameskuyper@verizon.net>
Newsgroups	comp.lang.c
Subject	Re: routine for angles needed
Date	2015-09-11 19:46 -0400
Organization	Self
Message-ID	<55F367F3.2000502@verizon.net> (permalink)
References	(9 earlier) <kfnr3mcww4j.fsf@x-alumni2.alumni.caltech.edu> <lntwr8v48u.fsf@kst-u.example.com> <msgj3f$apd$1@speranza.aioe.org> <55EC6281.4010500@verizon.net> <msvndk$81q$1@speranza.aioe.org>

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On 09/11/2015 07:17 PM, glen herrmannsfeldt wrote:
> James Kuyper <jameskuyper@verizon.net> wrote:
> 
> (snip, regarding decimal floating point, where I wrote)
> 
>>> Bit efficient is a funny term in this context. You can represent
>>> a specific number of real values with a given number of bits.
>  
>> Bit efficiency compares the number of real values representable by the
>> format under discussion, with 2^N, where N is the number of bits
>> required to store the format. If the first number is substantially
>> smaller than the second, the bits are being used inefficiently. This
>> seems a reasonable use of the term.
> 
> Yes, but it gets interesting in the floating point case.
> 
> You can allocate bits for exponent or significand, which changes
> the range and precision of the representable values. This complicates
> comparison between different representations that might have
> similar bit efficiency.

Range and precision are, indeed, other issues that need to be
considered. Bit efficiency is far from being the single most important
criterion for choosing a floating point format - it's just one criterion
among many. I was only defending the use of the term, which seemed to me
quite unobjectionable - Keith certainly wasn't promoting the idea that
it was the only thing to use when comparing formats.

Note: I should have said "the number of *distinct* real values
representable by the format under discussion". Distinctness isn't a big
issue for the binary floating point formats I'm most familiar with, but
I gather that it's a significant issue for IEEE 754-2008's decimal
floating point formats, with corresponding complications for correctly
calculating the bit efficiency:

"Because the significand is not normalized, most values with less than
16 significant digits have multiple possible representations;
1×102=0.1×103=0.01×104, etc. Zero has 768 possible representations (1536
if you include both signed zeros)."
<https://en.wikipedia.org/wiki/Decimal64_floating-point_format>

Thread

routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 10:17 -0700
  Re: routine for angles needed Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-08-02 10:38 -0700
    Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 11:10 -0700
      Re: routine for angles needed Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-08-02 11:26 -0700
        Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 11:41 -0700
          Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:02 -0700
  Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-02 18:41 +0100
    Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 11:43 -0700
      Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-02 20:00 +0100
        Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:04 -0700
          Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:10 -0700
            Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:24 -0700
              Re: routine for angles needed Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-08-02 12:32 -0700
                Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-02 20:40 +0100
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:59 -0700
                Re: routine for angles needed Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-08-02 13:14 -0700
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 13:39 -0700
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 13:45 -0700
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-03 07:48 -0700
                Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-03 17:06 +0100
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-03 09:09 -0700
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-03 09:17 -0700
                Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-03 17:48 +0100
                Re: routine for angles needed Keith Thompson <kst-u@mib.org> - 2015-08-03 13:44 -0700
                Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-03 23:51 +0100
                Re: routine for angles needed Keith Thompson <kst-u@mib.org> - 2015-08-03 18:30 -0700
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-03 23:11 +0000
                Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-04 01:32 +0100
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-04 01:14 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-08-03 20:26 -0500
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-04 18:24 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-08-05 01:46 -0500
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-05 18:06 +0000
                Re: routine for angles needed Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-05 11:37 -0700
                Re: routine for angles needed Keith Thompson <kst-u@mib.org> - 2015-09-05 16:24 -0700
                Re: routine for angles needed Richard Damon <Richard@Damon-Family.org> - 2015-09-05 21:01 -0400
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-09-05 23:30 -0500
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-06 05:37 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-09-07 00:27 -0500
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-06 05:31 +0000
                Re: routine for angles needed James Kuyper <jameskuyper@verizon.net> - 2015-09-06 11:57 -0400
                Re: routine for angles needed Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-09-06 17:44 +0100
                Re: routine for angles needed James Kuyper <jameskuyper@verizon.net> - 2015-09-06 14:02 -0400
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-12 00:05 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-09-07 00:31 -0500
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-12 00:00 +0000
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-11 23:17 +0000
                Re: routine for angles needed James Kuyper <jameskuyper@verizon.net> - 2015-09-11 19:46 -0400
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-12 03:56 +0000
                Re: routine for angles needed James Kuyper <jameskuyper@verizon.net> - 2015-09-12 12:33 -0400
                Re: routine for angles needed Richard Damon <Richard@Damon-Family.org> - 2015-09-12 14:29 -0400
                Re: routine for angles needed James Kuyper <jameskuyper@verizon.net> - 2015-09-12 15:58 -0400
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-13 06:21 +0000
                Re: routine for angles needed Keith Thompson <kst-u@mib.org> - 2015-09-06 11:59 -0700
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-12 00:16 +0000
                Re: routine for angles needed Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-06 18:04 -0700
                Re: routine for angles needed Keith Thompson <kst-u@mib.org> - 2015-09-06 18:30 -0700
                Re: routine for angles needed Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-09-06 18:48 -0700
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-09-07 00:44 -0500
                Re: routine for angles needed Tim Rentsch <txr@alumni.caltech.edu> - 2015-09-10 05:44 -0700
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-09-12 00:25 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-08-03 20:16 -0500
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-04 01:26 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-08-05 02:05 -0500
                Re: routine for angles needed Keith Thompson <kst-u@mib.org> - 2015-08-03 18:33 -0700
                Re: routine for angles needed glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-04 21:24 +0000
                Re: routine for angles needed Robert Wessel <robertwessel2@yahoo.com> - 2015-08-03 19:41 -0500
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:51 -0700
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 12:56 -0700
                Re: routine for angles needed Bartc <bc@freeuk.com> - 2015-08-02 20:57 +0100
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 13:06 -0700
                Re: routine for angles needed Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-08-02 22:25 +0100
                Re: routine for angles needed Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-08-02 22:27 +0100
                Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-02 14:40 -0700
  Re: routine for angles needed "Chris M. Thomasson" <nospam@nospam.nospam> - 2015-08-02 19:08 -0700
    Re: routine for angles needed fir <profesor.fir@gmail.com> - 2015-08-03 02:18 -0700
  Re: routine for angles needed danncorbit@gmail.com - 2015-08-12 02:18 -0700
  Re: routine for angles needed bartekltg <bartekltg@gmail.com> - 2015-09-07 05:02 +0200

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