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

From	"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups	comp.lang.c, comp.lang.c++
Subject	Re: what is the best way to get microseconds of time on Windows in C or C++ ?
Date	2022-11-04 15:56 -0700
Organization	A noiseless patient Spider
Message-ID	<tk45ai$22881$1@dont-email.me> (permalink)
References	<tk1p0t$1iv03$1@dont-email.me> <tk2fch$13ej$1@gioia.aioe.org> <tk3oto$1va6e$1@dont-email.me> <8735ayml3k.fsf@nosuchdomain.example.com> <tk4432$21usu$1@dont-email.me>

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On 11/4/2022 3:35 PM, Lynn McGuire wrote:
> On 11/4/2022 5:05 PM, Keith Thompson wrote:
>> Lynn McGuire <lynnmcguire5@gmail.com> writes:
>>> On 11/4/2022 2:35 AM, Juha Nieminen wrote:
>>>> In comp.lang.c++ Lynn McGuire <lynnmcguire5@gmail.com> wrote:
>>>>> What is the best way to get microseconds of time on Windows in C or 
>>>>> C++
>>>> It's a bit unclear whether you mean "time in microseconds units" or
>>>> "time
>>>> at the microseconds resolution".
>>>> Because the latter may not be even possible (portable or not). Just
>>>> because
>>>> some time function returns time "in microseconds" that doesn't mean 
>>>> that it
>>>> uses microsecond resolution (in other words, the value it returns 
>>>> may well
>>>> change at longer intervals than every microsecond; probably 
>>>> *significantly*
>>>> longer intervals).
>>>> It is possible to get some kind of timing at the CPU clock cycle
>>>> interval
>>>> (in most modern CPUs, at least), which is about as accurate as you can
>>>> possibly get, but I don't know if there are eg. some system 
>>>> functions that
>>>> will return elapsed clock cycles converted into the equivalent 
>>>> amount of
>>>> microseconds.
>>>
>>> Get time at the microseconds resolution.   My calculation engine
>>> creates a bunch of temporary files and I use the time to create unique
>>> names for those temporary files.  Seconds should be good enough for
>>> uniqueness but I like adding microseconds as a guarantee.  Something
>>> like
>>>     uniquac1.out.009.20181972.20220912
>>
>> An alternative is to keep a counter, incremented for each generated file
>> name, and append it to the file name, perhaps resetting to 0 when the
>> seconds count advances.  If your only requirement is uniqueness, that
>> should be good enough.
>>
>> Digression: I remember an implementation of gettimeofday() that did
>> something like that (on SunOS, maybe?).  The system clock had a
>> resolution of 0.01 second, so the value of tv_usec on successive calls
>> might be:
>>      420000
>>      420001
>>      420002
>>      430000
>>      430001
>>      430002
>>      ...
>> I don't remember whether the implicit counter was per-process or
>> system-wide.
> 
> The problem is multiple instances of the same program creating the same 
> name files.

Prepend the file names with the PID? Something to make it unique. 
Perhaps a SHA2-HMAC or something.

Thread

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++ ? DFS <nospam@dfs.com> - 2022-11-03 21:51 -0400
    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++ ? 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++ ? 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++ ? Bart <bc@freeuk.com> - 2022-11-04 22:31 +0000
      Re: what is the best way to get microseconds of time on Windows in C or C++ ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-11-05 06:40 +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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