Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #94838

Re: CLOCKS_PER_SEC

Show all headers | View raw

Keith Thompson <kst-u@mib.org> writes:

> Lowell Gilbert <lgusenet@be-well.ilk.org> writes:
>> Keith Thompson <kst-u@mib.org> writes:
>>> BartC <bc@freeuk.com> writes:
>>>> CLOCKS_PER_SEC determines how the result of the clock() function is 
>>>> interpreted.
>>>>
>>>> But it seems to be defined as macro in time.h.
>>>>
>>>> Any ideas on how to determine that value when calling clock() as foreign 
>>>> function from another language? I want to avoid OS-specific functions 
>>>> unless they are available on both Windows and Linux.
>>>>
>>>> (At the moment, CLOCKS_PER_SEC seems to be usually 1000 on Windows and 
>>>> 1000000 on Linux. I suppose I could detect abnormally large values of 
>>>> clock() and infer it that way, but I think there will be some overlap in 
>>>> the set of valid results.)
>>>
>>> Write a C function that returns the value of the macro, and call that
>>> function from the foreign language.  Depending on your build system, you
>>> can probably do this at configuration time rather than at run time.
>>
>> Or write a wrapper that returns the equivalent in nanoseconds.
>
> Assuming that 1/CLOCKS_PER_SEC is a whole number of nanoseconds.
> (I don't object to making the assumption, I'm just pointing out
> that it is one.)

Well, 10^9 rather than 1.

I don't think that assumption is actually required; rounding to
the nearest nanosecond is not going to introduce additional error
in any existing implementations I know, and that probably won't
change in the near future.

But, yes, I was making an implicit assumption that nanoseconds
can adequately represent the time value involved.


-- 
Lowell Gilbert, embedded/networking software engineer
	 http://be-well.ilk.org/~lowell/

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

CLOCKS_PER_SEC BartC <bc@freeuk.com> - 2016-10-13 14:49 +0100
  Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-13 08:57 -0700
    Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-13 09:07 -0700
      Re: CLOCKS_PER_SEC BartC <bc@freeuk.com> - 2016-10-13 23:18 +0100
        Re: CLOCKS_PER_SEC BartC <bc@freeuk.com> - 2016-10-13 23:30 +0100
          Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-13 16:27 -0700
            Re: CLOCKS_PER_SEC raltbos@xs4all.nl (Richard Bos) - 2016-10-16 10:02 +0000
              Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-16 11:32 -0700
    Re: CLOCKS_PER_SEC Lowell Gilbert <lgusenet@be-well.ilk.org> - 2016-10-13 12:19 -0400
      Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-13 11:29 -0700
        Re: CLOCKS_PER_SEC Lowell Gilbert <lgusenet@be-well.ilk.org> - 2016-10-13 14:39 -0400
          Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-13 12:03 -0700
        Re: CLOCKS_PER_SEC supercat@casperkitty.com - 2016-10-14 07:47 -0700
  Re: CLOCKS_PER_SEC Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-10-14 16:21 +0300
    Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-14 08:41 -0700
      Re: CLOCKS_PER_SEC Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-10-14 18:56 +0300
        Re: CLOCKS_PER_SEC Barry Schwarz <schwarzb@dqel.com> - 2016-10-14 09:49 -0700
        Re: CLOCKS_PER_SEC Keith Thompson <kst-u@mib.org> - 2016-10-14 11:14 -0700
          Re: CLOCKS_PER_SEC supercat@casperkitty.com - 2016-10-14 11:32 -0700
      Re: CLOCKS_PER_SEC Jerry Stuckle <jstucklex@attglobal.net> - 2016-10-14 11:56 -0400
        Re: CLOCKS_PER_SEC Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-10-14 19:53 +0300
          Re: CLOCKS_PER_SEC supercat@casperkitty.com - 2016-10-14 09:57 -0700
          Re: CLOCKS_PER_SEC BartC <bc@freeuk.com> - 2016-10-14 18:18 +0100
        Re: CLOCKS_PER_SEC Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-10-16 02:55 -0700

csiph-web