Re: How to div only once to get remainder and quotient?

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c
Subject	Re: How to div only once to get remainder and quotient?
Date	2020-03-13 19:06 +0100
Organization	A noiseless patient Spider
Message-ID	<r4gi2c$44h$1@dont-email.me> (permalink)
References	(2 earlier) <4MJaG.445254$QS6.115982@fx02.am4> <r4g1vj$c9k$1@dont-email.me> <hpNaG.773884$CR7.485190@fx40.am4> <r4gece$8li$1@dont-email.me> <oUPaG.656784$p%3.429025@fx26.am4>

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On 13/03/2020 19:01, Bart wrote:
> On 13/03/2020 17:03, David Brown wrote:
>> On 13/03/2020 16:12, Bart wrote:
>>> On 13/03/2020 13:31, David Brown wrote:
>>>> On 13/03/2020 12:03, Bart wrote:
>>>
>>>
>>>>> If each result will always be written individually by printf or puts,
>>>>> that may be true. But the code might end up in a function that writes
>>>>> millions of binary strings to memory (maybe, later writing that to a
>>>>> file as one memoryblock).
>>>>
>>>> Please re-read what I wrote.  I did not say efficiency is irrelevant
>>>> - I
>>>> said code clarity is much more important, and micro-efficiency
>>>> should be
>>>> ignored unless you know it really is an issue.  In this code, it very
>>>> clearly is /not/ an issue.
>>>
>>> It seemed very likely to me that the puts was just there to test the
>>> output, enough that you can't say that the efficiency of such a routine
>>> 'clearly' wasn't relevant.
>>>
>>
>> It seems equally likely that the primary purpose of turning an integer
>> into a string of 0 and 1 characters is to print it out somewhere (to a
>> terminal, file, etc.).
> ...
>> In the conversion itself, decimal is often more time-consuming because
>> you are dividing by 10, not a power of 2.  But you almost invariably
>> want to do something with the resulting string that is a great deal more
>> time-consuming than the conversion.
> 
> I think the result of most such conversions will never be displayed.
> 
> Think of generating HLL source code, ASM source, CSV files, XML,
> listings files, log files, or just piping the output to another process,
> or directing it to a file.

It doesn't matter.  All of these will take many orders of magnitude more
processor cycles than a division, or the entire conversion to binary digits.

> 
> So perhaps the most time-consuming thing might be turning it back into
> binary. Which usually involves multiplies rather than divides.

Multiplication by powers of two is not time-consuming for a cpu.

> 
> (Eg. gcc appears to work by generating .s files which are then processed
> by 'as'.)

Yes.  And one of the reasons no one has made a big effort to change
that, is that it is such a minor part of the time taken for the
compilation process.  (Effort /is/ taken to have the temporary assembly
files kept in memory rather than written out as files to a disk.)

Thread

How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-12 20:18 +0000
  Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-12 20:26 +0000
    Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-12 20:30 +0000
      Re: How to div only once to get remainder and quotient? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-03-12 20:40 -0700
    Re: How to div only once to get remainder and quotient? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-03-12 16:38 -0400
      Re: How to div only once to get remainder and quotient? richard@cogsci.ed.ac.uk (Richard Tobin) - 2020-03-12 20:44 +0000
        Re: How to div only once to get remainder and quotient? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-03-12 17:00 -0400
          Re: How to div only once to get remainder and quotient? richard@cogsci.ed.ac.uk (Richard Tobin) - 2020-03-13 09:35 +0000
            Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-13 11:12 +0100
      Re: How to div only once to get remainder and quotient? scott@slp53.sl.home (Scott Lurndal) - 2020-03-12 22:16 +0000
        Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-12 22:39 +0000
          Re: How to div only once to get remainder and quotient? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-03-12 19:51 -0400
            Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-13 00:47 +0000
              Re: How to div only once to get remainder and quotient? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-03-12 23:02 -0400
              Re: How to div only once to get remainder and quotient? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-03-12 20:39 -0700
            Re: How to div only once to get remainder and quotient? scott@slp53.sl.home (Scott Lurndal) - 2020-03-13 15:00 +0000
            Re: How to div only once to get remainder and quotient? Spiros Bousbouras <spibou@gmail.com> - 2020-03-14 08:35 +0000
  Re: How to div only once to get remainder and quotient? jak <nospam@please.ty> - 2020-03-12 21:55 +0100
    Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-12 21:56 +0000
      Re: How to div only once to get remainder and quotient? jak <nospam@please.ty> - 2020-03-12 23:26 +0100
  Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-12 21:11 +0000
    Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-12 21:57 +0000
    Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-12 22:23 +0000
      Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-13 01:05 +0000
  Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-13 11:33 +0100
    Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-13 11:03 +0000
      Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-13 14:31 +0100
        Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-13 15:12 +0000
          Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-13 18:03 +0100
            Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-13 18:01 +0000
              Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-13 19:06 +0100
                Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-13 19:12 +0000
      Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-13 13:34 +0000
        Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-13 15:00 +0000
          Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-13 20:34 +0000
            Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-13 21:41 +0000
              Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-14 01:47 +0000
                Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-14 12:24 +0000
                Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-14 16:35 +0000
                Re: How to div only once to get remainder and quotient? Bart <bc@freeuk.com> - 2020-03-14 18:05 +0000
  Re: How to div only once to get remainder and quotient? already5chosen@yahoo.com - 2020-03-13 03:52 -0700
  Re: How to div only once to get remainder and quotient? Guillaume <message@bottle.org> - 2020-03-13 16:41 +0100
    Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-13 16:07 +0000
      Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-13 18:10 +0100
        Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-13 19:32 +0000
          Re: How to div only once to get remainder and quotient? James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-03-13 16:08 -0400
            Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-13 20:50 +0000
              Re: How to div only once to get remainder and quotient? jameskuyper@stellarscience.com - 2020-03-13 16:05 -0700
                Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-13 23:42 +0000
                Re: How to div only once to get remainder and quotient? James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-03-13 19:59 -0400
                Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-14 00:07 +0000
                Re: How to div only once to get remainder and quotient? James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-03-13 20:27 -0400
                Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-14 01:37 +0000
                Re: How to div only once to get remainder and quotient? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-02 07:45 -0700
                Re: How to div only once to get remainder and quotient? James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-02 08:09 -0700
                Re: How to div only once to get remainder and quotient? gazelle@shell.xmission.com (Kenny McCormack) - 2020-04-02 16:03 +0000
                Re: How to div only once to get remainder and quotient? Öö Tiib <ootiib@hot.ee> - 2020-04-04 04:31 -0700
                Invitations (Was: How to div only once to get remainder and quotient?) gazelle@shell.xmission.com (Kenny McCormack) - 2020-04-04 17:04 +0000
                Re: Invitations (Was: How to div only once to get remainder and quotient?) Öö Tiib <ootiib@hot.ee> - 2020-04-07 00:10 -0700
      Re: How to div only once to get remainder and quotient? James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-03-13 14:30 -0400
        Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-13 20:54 +0000
          Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-13 23:10 +0000
          Re: How to div only once to get remainder and quotient? James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-03-13 20:18 -0400
            Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-14 00:34 +0000
              Re: How to div only once to get remainder and quotient? Francis Assissi <invalid@invalid.invalid> - 2020-03-14 01:47 +0000
  Re: How to div only once to get remainder and quotient? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-03-13 14:39 -0600
    Re: How to div only once to get remainder and quotient? felix@palmen-it.de (Felix Palmen) - 2020-03-13 22:10 +0100
      Re: How to div only once to get remainder and quotient? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-03-13 16:26 -0600
      Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-14 16:41 +0100
        Re: How to div only once to get remainder and quotient? felix@palmen-it.de (Felix Palmen) - 2020-03-14 17:00 +0100
          Re: How to div only once to get remainder and quotient? David Brown <david.brown@hesbynett.no> - 2020-03-15 13:39 +0100
    Re: How to div only once to get remainder and quotient? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-13 23:07 +0000
      Re: How to div only once to get remainder and quotient? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-03-14 12:13 -0600
  Re: How to div only once to get remainder and quotient? Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-07 09:35 +0200

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