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Groups > comp.lang.c > #92642

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 15:14 +0100
Organization A noiseless patient Spider
Message-ID <87shtvr2rg.fsf@bsb.me.uk> (permalink)
References (16 earlier) <npgak4$13a$1@jstuckle.eternal-september.org> <npgui2$hjt$1@dont-email.me> <nphepg$1dn$3@jstuckle.eternal-september.org> <nphhqp$db1$1@dont-email.me> <nphjp1$k66$1@jstuckle.eternal-september.org>

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Jerry Stuckle <jstucklex@attglobal.net> writes:

> On 8/23/2016 9:07 AM, David Brown wrote:
<snip>
>> And in either case, I can't see why storing 9 digits in 32-bit chunks is
>> going to be much more complicated than storing 1 or 2 digits in 8-bit
>> chunks (BCD, packed or unpacked).  It will certainly be more efficient
>> for calculations.  18 digits in 64-bit chunks is going to be even better
>> on modern cpus.

Maybe.  The advantage of base 10^9 is that the result of any single
digit multiplication fits in 64 bits.  If you have a 64-bit to 128-bit
multiply them, sure, use base 10^18, but if you don't, or you want to
write the code in portable C, then 10^9 is probably better.

> Then you show how to subtract 123.456 from 789012.345678 using 18 digits
> in 64 bit chunks.  I'd love to see you do it.

It's the same as I showed for base 1,000,000,000 only base 10^18.  The
numbers are represented with two digits -- one before and one after the
point.  The position of the point is signalled with a count:

  (1, [789012, 345678000000000000]) - (1, [123, 456000000000000000])

Again, because 456000000000000000 > 345678000000000000 the subtraction
involves a "borrow" to give:

  (1, [789012 - 123 - 1, 10^18 + 345678000000000000 - 456000000000000000])

> But you've already shown you have no clue, so I won't hold my breath.

Ah, the insults are starting.

-- 
Ben.

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Thread

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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