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Re: Float Vs Double

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Float Vs Double
Date 2016-08-23 14:47 +0100
Organization A noiseless patient Spider
Message-ID <87zio3r400.fsf@bsb.me.uk> (permalink)
References (15 earlier) <npg1jd$b3k$2@jstuckle.eternal-september.org> <874m6ctktg.fsf@bsb.me.uk> <npgak4$13a$1@jstuckle.eternal-september.org> <87inurstnl.fsf@bsb.me.uk> <nphes2$1dn$4@jstuckle.eternal-september.org>

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Jerry Stuckle <jstucklex@attglobal.net> writes:

> On 8/23/2016 5:48 AM, Ben Bacarisse wrote:
>> Jerry Stuckle <jstucklex@attglobal.net> writes:
>> 
>>> On 8/22/2016 8:01 PM, Ben Bacarisse wrote:
>>>> Jerry Stuckle <jstucklex@attglobal.net> writes:
>>>>
>>>>> On 8/22/2016 11:39 AM, supercat@casperkitty.com wrote:
>> <snip>
>>>>>> I'm surprised I haven't seen more "decimal math" libraries using 9 digits
>>>>>> per word; such a thing would seem like a natural fit on a 32-bit processor
>>>>>> with a 32x32->64 multiply.  Performance would be likely slower than for
>>>>>> binary math, but nowhere near as slow as using single-digit or two-digit
>>>>>> chunks (on processors which can't use a carry flag for extended-precision
>>>>>> math, addition and subtraction could benefit from the fact that the sum
>>>>>> or difference of any two 9-digit chunks could fit in a 32-bit
>>>>>> signed "int").
>>>>>>
>>>>>
>>>>> 9 digits per word would not be decimal math.  The most you could get
>>>>> into 32 bits would be 8 decimal digits.
>>>>
>>>> I think what supercat is talking about might otherwise be called base
>>>> 1,000,000,000 arithmetic.
>>>>
>>>>> And I suspect trying it would
>>>>> be even slower than decimal math.  It would be much more complicated to
>>>>> implement.
>>>>
>>>> In software, it's faster and simpler than using BCD-type schemes, but
>>>> it's a matter of definition if is a decimal scheme or not.
>>>>
>>>
>>> I understand what he's after, and my comments stand.  For instance, how
>>> easy would it be to subtract 123.456 from 789012.345678?  Not that hard
>>> with BCD, but very difficult with supercat's idea.  Adjusting for the
>>> decimal point would not be easy.
>> 
>> I think you have missed what he's suggesting.  Your example subtraction
>> is very easy in base 1,000,000,000 arithmetic.  One simple
>> representation might be
>> 
>>  (1, [789012, 345678000]) - (1, [123, 456000000])
>> 
>> The 1 showing that both have 1 digit after the point.  Even using a
>> naive algorithm, the whole operation will take two subtractions, an add
>> and a decrement.
>
> No, I did not miss his suggestion.  What YOU miss is the fact that in
> the real world, numbers generally don't all have the same number of
> decimal places.

No, you claimed the subtraction you gave was "very hard".  You obviously
did not understand what was being suggested or you would have given an
example that was, at least, not trivial.  If you like, try again to post
a "very hard" subtraction, but there are none -- it's a simple scheme.
It maybe time for you to start insulting me.

> So your code doesn't work.

I posted no code, but I *have* implemented this scheme (more than once)
and it is very simple.

-- 
Ben.

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Float Vs Double Real Troll <real.troll@trolls.com> - 2016-08-07 17:59 -0400
  Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-07 23:38 +0100
  Re: Float Vs Double Real Troll <real.troll@trolls.com> - 2016-08-07 18:55 -0400
    Re: Float Vs Double jameskuyper@verizon.net - 2016-08-07 16:43 -0700
      Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-07 19:36 -0700
        Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 04:05 +0100
          Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-07 20:41 -0700
            Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 11:41 +0100
              Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-08 04:23 -0700
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-08 23:45 +0100
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-10 03:26 -0700
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-11 01:00 +0100
        Re: Float Vs Double jameskuyper@verizon.net - 2016-08-08 08:52 -0700
          Re: Float Vs Double James Kuyper <jameskuyper@verizon.net> - 2016-08-08 11:58 -0400
          Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-08 10:06 -0700
      Re: Float Vs Double "James R. Kuyper" <jameskuyper@verizon.net> - 2016-08-08 19:46 -0400
    Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-07 21:29 -0400
      Re: Float Vs Double jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-08 14:04 +0200
        Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-08 09:00 -0400
          Re: Float Vs Double jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-08 18:43 +0200
            Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-08 14:34 -0400
              Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-08 12:00 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-08 16:42 -0400
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-08 14:04 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-09 08:48 -0400
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-10 03:22 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-21 18:31 -0400
                Re: Float Vs Double supercat@casperkitty.com - 2016-08-22 08:39 -0700
                Re: Float Vs Double Jean-Marc Bourguet <jm@bourguet.org> - 2016-08-22 19:29 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-22 19:24 -0400
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-23 01:01 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-22 21:58 -0400
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-23 09:38 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 08:15 -0400
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-23 15:07 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 09:40 -0400
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-23 15:14 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 10:38 -0400
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-23 17:18 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 15:47 -0400
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-23 16:39 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 11:45 -0400
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-23 21:42 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 15:52 -0400
                Re: Float Vs Double Ian Collins <ian-news@hotmail.com> - 2016-08-24 08:36 +1200
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-24 09:39 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-24 11:31 -0400
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-23 10:48 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 08:17 -0400
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-23 06:01 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 09:44 -0400
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-23 07:19 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 10:39 -0400
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-23 08:18 -0700
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-23 14:47 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 10:40 -0400
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-24 01:31 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-23 20:53 -0400
                Re: Float Vs Double supercat@casperkitty.com - 2016-08-23 23:20 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-24 11:32 -0400
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-24 09:46 +0200
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-24 14:53 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-24 11:35 -0400
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-24 08:57 -0700
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-24 17:36 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-24 12:50 -0400
                Re: Float Vs Double Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-24 17:26 +0100
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-24 12:51 -0400
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-24 11:33 -0400
                Re: Float Vs Double Robert Wessel <robertwessel2@yahoo.com> - 2016-08-28 02:33 -0500
                Re: Float Vs Double antispam@math.uni.wroc.pl - 2016-08-31 22:36 +0000
                Re: Float Vs Double supercat@casperkitty.com - 2016-08-31 15:51 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-31 22:42 -0400
                Re: Float Vs Double supercat@casperkitty.com - 2016-09-01 08:32 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-01 15:00 -0400
                Re: Float Vs Double supercat@casperkitty.com - 2016-09-01 13:45 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-01 20:50 -0400
                Re: Float Vs Double supercat@casperkitty.com - 2016-09-02 08:11 -0700
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 12:25 -0400
                Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-09-02 20:42 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-02 16:25 -0400
                Re: Float Vs Double Jean-Marc Bourguet <jm@bourguet.org> - 2016-09-03 08:43 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 10:48 -0400
                Re: Float Vs Double Jean-Marc Bourguet <jm@bourguet.org> - 2016-09-03 19:43 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 18:16 -0400
                Re: Float Vs Double asetofsymbols@gmail.com - 2016-09-08 11:18 -0700
                Re: Float Vs Double Robert Wessel <robertwessel2@yahoo.com> - 2016-09-07 19:59 -0500
                Re: Float Vs Double supercat@casperkitty.com - 2016-09-08 08:13 -0700
                Re: Float Vs Double Robert Wessel <robertwessel2@yahoo.com> - 2016-09-08 19:34 -0500
                Re: Float Vs Double supercat@casperkitty.com - 2016-09-09 07:50 -0700
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-09-02 23:40 -0700
                Re: Float Vs Double Jean-Marc Bourguet <jm@bourguet.org> - 2016-09-03 09:06 +0200
                Re: Float Vs Double Jerry Stuckle <jstucklex@attglobal.net> - 2016-09-03 10:52 -0400
                Re: Float Vs Double Rosario19 <Ros@invalid.invalid> - 2016-08-24 08:57 +0200
                Re: Float Vs Double Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-24 01:04 -0700
    Re: Float Vs Double Ike Naar <ike@iceland.freeshell.org> - 2016-08-08 06:44 +0000
      Re: Float Vs Double Keith Thompson <kst-u@mib.org> - 2016-08-08 00:16 -0700
        Re: Float Vs Double Richard Damon <Richard@Damon-Family.org> - 2016-08-08 23:29 -0400
    Re: Float Vs Double jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-08 14:03 +0200
      Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-08 05:14 -0700
        Re: Float Vs Double BGB <cr88192@hotmail.com> - 2016-08-09 19:53 -0500
  Re: Float Vs Double "James R. Kuyper" <jameskuyper@verizon.net> - 2016-08-07 18:47 -0400
  Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-07 17:04 -0700
    Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-08 05:49 -0700
    Re: Float Vs Double Nobody <nobody@nowhere.invalid> - 2016-08-10 03:26 +0100
      Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-09 20:15 -0700
        Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-10 06:07 -0700
      Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-10 06:13 -0700
        Re: Float Vs Double David Brown <david.brown@hesbynett.no> - 2016-08-10 16:43 +0200
          Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-10 07:56 -0700
          Re: Float Vs Double supercat@casperkitty.com - 2016-08-10 08:39 -0700
            Re: Float Vs Double Keith Thompson <kst-u@mib.org> - 2016-08-10 09:56 -0700
              Re: Float Vs Double Keith Thompson <kst-u@mib.org> - 2016-08-10 10:04 -0700
                Re: Float Vs Double Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-11 07:08 -0700
                Re: Float Vs Double "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-08-11 07:15 -0700
                Re: Float Vs Double Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-12 08:11 -0700
              Re: Float Vs Double jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-10 20:38 +0200
                Re: Float Vs Double Keith Thompson <kst-u@mib.org> - 2016-08-10 12:20 -0700
                Re: Float Vs Double supercat@casperkitty.com - 2016-08-10 12:17 -0700
                Re: Float Vs Double jacobnavia <jacob@jacob.remcomp.fr> - 2016-08-10 21:48 +0200
                Re: Float Vs Double Keith Thompson <kst-u@mib.org> - 2016-08-10 13:40 -0700
              Re: Float Vs Double Ian Collins <ian-news@hotmail.com> - 2016-08-12 08:01 +1200
          Re: Float Vs Double BGB <cr88192@hotmail.com> - 2016-08-10 15:00 -0500

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