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Re: What does clock() return?
- From: Tim Prince <tprince at computer dot org>
- To: "Alex Vinokur" <alexvn at connect dot to>,cygwin at cygwin dot com
- Date: Thu, 08 Jul 2004 05:20:45 -0700
- Subject: Re: What does clock() return?
- References: <cciguv$e7o$1@sea.gmane.org>
At 09:01 PM 7/7/2004, Alex Vinokur wrote:
Here is an article
http://groups.google.com/groups?selm=2l2ucgF7jv50U1%40uni-berlin.de
from http://groups.google.com/groups?group=microsoft.public.vc.language
"Victor Bazarov" <v.Abazarov@comAcast.net> wrote in message
news:%23gH7pzEZEHA.992@TK2MSFTNGP10.phx.gbl...
> Is it a known issue that in VC++ RTL the function 'clock()'
> reports the wall clock instead of CPU time used? I ran this
> test program on Windows and Unix:
A long standing "problem." As Win9x had no choice other than wall clock
time, MSVCRTL gives you no choice. Other compiler vendors make the choice
according to which version of Windows is running. If you choose
ProcessTime(), the resolution is 0.010 seconds, which is unsatisfactory for
many small benchmarks, so then we must over-ride it by using the rdtsc
counter directly.
Here is my understanding of the decision: for cygwin, the primary goal is
compatibility with gcc running on other OS. For mingw, the goal is
compatibility with Microsoft practice, where feasible. Thus, no chance of
compatibility between mingw and cygwin on this point.
Tim Prince
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