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Re: what is the best way to get microseconds of time on Windows in C or C++ ?

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On 11/4/2022 5:12 AM, Michael S wrote:
> On Friday, November 4, 2022 at 3:14:23 AM UTC+2, Lynn McGuire wrote:
>> What is the best way to get microseconds of time on Windows in C or C++
>> ? I am currently using the following code to get the current time:
>>
>> std::time_t t = std::time (0); // get time now
>> std::tm * now = std::localtime ( & t);
>> integer iyear = now -> tm_year + 1900;
>> integer imonth = now -> tm_mon + 1;
>> integer iday = now -> tm_mday;
>> integer ihour = now -> tm_hour;
>> integer imin = now -> tm_min;
>> integer isec = now -> tm_sec;
>> integer ihund = 0;
>>
>> Thanks,
>> Lynn
> 
> Are you interested in absolute time or in measuring time intervals
> for profiling and similar purposes?
> 
> For the former, usec resolution is obviously impossible, because
> crystals that drive time measurement in your typical PC are not
> very good and time adjustments via NTP are not particularly frequent.
> Not just microseconds, even whole second are typically no good.
>    
> For the later, as long as measured intervals are relatively short
> (no more than 10-20 msec) usec resolution is physically possible.
> 
> The most portable way is std::chrono::steady_clock.
> 
> Less portable way (unreliable with Windows+gcc under mingw)
> but good with Windows+MSVC and Linux+gcc, is
> std::chrono::high_resolution_clock
> 
> Another good way that is not portable in absolute sense, but
> very portable between various x86 OSes and environments
> is __rdtsc(). Except that I am not aware of portable way of
> figuring out a duration of the tick. Well, except of calibration
> followed by rounding to nearest 50MHz, but that method is
> non-satisfactory.
> In practice, quite often you just know the frequency. And
> even more often non-portable way of finding it is good enough.

Both measuring time intervals and the current time.

Thanks !

Lynn

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what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-03 20:14 -0500
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 00:06 -0500
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Christian Gollwitzer <auriocus@gmx.de> - 2022-11-04 08:03 +0100
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 14:32 -0500
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-11-04 09:07 -0700
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 14:33 -0500
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Opus <ifonly@youknew.org> - 2022-11-06 20:53 +0100
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-06 14:30 -0800
        Re: what is the best way to get microseconds of time on Windows in C or C++ ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-11-07 07:48 +0100
          Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-07 04:11 -0800
            Re: what is the best way to get microseconds of time on Windows in C or C++ ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-11-08 18:30 +0100
              Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-08 15:37 -0800
                Re: what is the best way to get microseconds of time on Windows in C or C++ ? Öö Tiib <ootiib@hot.ee> - 2022-11-09 06:14 -0800
                Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-12 16:21 -0800
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? Juha Nieminen <nospam@thanks.invalid> - 2022-11-04 07:35 +0000
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 14:24 -0500
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-04 19:50 +0000
        Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 15:16 -0500
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-11-04 15:05 -0700
        Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 17:35 -0500
          Re: what is the best way to get microseconds of time on Windows in C or C++ ? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-11-04 15:56 -0700
          Re: what is the best way to get microseconds of time on Windows in C or C++ ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-11-04 16:15 -0700
          Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-06 14:41 -0800
            Re: what is the best way to get microseconds of time on Windows in C or C++ ? scott@slp53.sl.home (Scott Lurndal) - 2022-11-07 14:39 +0000
              Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-07 11:03 -0800
            Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-07 23:26 -0600
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? Öö Tiib <ootiib@hot.ee> - 2022-11-04 01:23 -0700
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Juha Nieminen <nospam@thanks.invalid> - 2022-11-07 07:20 +0000
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Öö Tiib <ootiib@hot.ee> - 2022-11-07 07:11 -0800
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? Michael S <already5chosen@yahoo.com> - 2022-11-04 03:12 -0700
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 14:35 -0500
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? scott@slp53.sl.home (Scott Lurndal) - 2022-11-04 13:44 +0000
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-04 14:34 -0500
    Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-14 16:58 -0600
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-11-14 17:36 -0800
        Re: what is the best way to get microseconds of time on Windows in C or C++ ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-11-15 17:26 -0600
          Re: what is the best way to get microseconds of time on Windows in C or C++ ? Andreas <nospam@gmx.de> - 2022-11-16 13:15 +0100
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-11-04 20:49 +0100
  Re: what is the best way to get microseconds of time on Windows in C or C++ ? Manu Raju <MR@invalid.invalid> - 2022-11-20 21:30 +0000

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