2013/11/23 Óscar Fuentes <[email protected]>
> Hello Ruben,
>
> Ruben Van Boxem <[email protected]>
> writes:
>
> > This is comparable to the output I get from VS2013. So I would say this
> is
> > a quality of implementation issue (wrt the resolution of the clock
> used).
> > I doubt though that this is nonconformant. I didn't look up the exact
> > chrono requirements in the standard though.
> >
> > What exactly do you think is "broken" here beyond a bad resolution?
>
> I don't think that the jump it makes from 0 to 15e6 for a 10-fold
> increase on iterations is about resolution. The output sometimes is 0
> for the last line too.
>
True, further testing showed me the same kind of weirdness.
>
> But you are right about VS2013, although that doesn't mean much given
> the quality of that release (I'm considering switching to MinGW-W64 from
> VS2010 after finding blocking bugs on VS2013.)
>
> It can be a QoI issue indeed, but the fact that boost gives reasonable
> values tells us that MinGW-W64 and VS2013 could do much better.
>
You're absolutely right! I believe the clocks are implemented on top of
additional POSIX timing functionality Kai/JonY put into winpthreads and/or
MinGW-w64.
I bet Boost uses QueryPerformanceCounter and friends to get ubertiming on
Windows. libstdc++ would do good to specialize a bit, but as there is no
motivated Windows maintainer, all other maintainers are unfortunately a bit
"anxious" towards Windows only improvements :-/ So this basically means
MinGW-w64 needs to improve its POSIX compatibility stuff when possible :-)
>
> I'll investigate further.
>
Please share your findings (if any) with the list, I'm sure the devs will
be interested to know how to improve the situation.
Ruben
>
>
>
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