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From: Hung Nguyen Vu (vuhung16plus+shape_at_[hidden])
Date: 2008-07-25 04:56:38
On Fri, Jul 25, 2008 at 5:29 PM, Bruno Lalande <bruno.lalande_at_[hidden]>
wrote:
> > What platform is that?
>
> A very common one: Linux 2.6 with GCC 4.1 or 4.2. The distribution is
> Kubuntu.
>
> timer().elapsed_max() gives 2147.48 on this platform and indeed,
> elapsed() returns negative numbers above that time (before returning
> to 0).
>
> I had thought about the possibility of making a policy-based version
> of boost::timer, with something like a "heart policy" that would
> define the way in which the time would be obtained and stored
> internally. There would be a portable one (the one of boost::timer
> currently), another one based on boost::date_time, and why not some
> platform-specific ones (QueryPerformanceCounter on windows for
> instance). But I never had the time to dig more :-(
>
>
I don't mean to hijack the thread but please let me share another way to use
timer,
with C, not C++ or boots. In the code, not only the time of one test, but
average time,
and its standard derivation are calculated so we will know how "close" is
the average time.
My question: Is there any similar implementation in boost?
The code is as follows:
int count = 30;
long long times[count];
for (i = 0; i < count; i++) ï½
time start;
gettimeofday (&start, NULL);
// do something
gettimeofday (&end, NULL);
long long time = ((end.tv_sec - start.tv_sec) * 1000000 +
(end.tv_usec - start.tv_usec));
times[i] = time;
}
// and use it
printf("mean: %f, stddev: %f\n", mean(times, 20), stddev(times, 20);
double
variance (long long *x, int n)
{ double m = x[0];
double s = 0;
int i;
for (i = 0; i < n; i++)
{
double m_new = m + (x[i] - m) / (i + 1);
s = s + (x[i] - m) * (x[i] - m_new);
m = m_new;
}
return s / (n - 1);
}
double
mean (long long *x, int n)
{ double m = x[0];
int i;
for (i = 0; i < n; i++)
{
m = m + (x[i] - m) / (i + 1);
}
return m;
}
double
stddev (long long *x, int n)
{
return sqrt (variance (x, n));
}
-- Best Regards, Nguyen Hung Vu ( Nguyá» n VÅ© HÆ°ng ) vuhung16plus{remove}@gmail.dot.com <vuhung16plus%7Bremove%7D_at_[hidden]>, YIM: vuhung16 , Skype: vuhung16dg Japan through an eye of a gaijin: http://www.flickr.com/photos/vuhung/tags/fav/
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