This is the mail archive of the
glibc-bugs@sourceware.org
mailing list for the glibc project.
[Bug libc/15424] modf benchtest gives bogus results
- From: "neleai at seznam dot cz" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Fri, 10 May 2013 09:16:24 +0000
- Subject: [Bug libc/15424] modf benchtest gives bogus results
- Auto-submitted: auto-generated
- References: <bug-15424-131 at http dot sourceware dot org/bugzilla/>
http://sourceware.org/bugzilla/show_bug.cgi?id=15424
--- Comment #2 from Ondrej Bilka <neleai at seznam dot cz> 2013-05-10 09:16:24 UTC ---
On Fri, May 10, 2013 at 08:19:48AM +0000, siddhesh at redhat dot com wrote:
> http://sourceware.org/bugzilla/show_bug.cgi?id=15424
>
> Siddhesh Poyarekar <siddhesh at redhat dot com> changed:
>
> What |Removed |Added
> ----------------------------------------------------------------------------
> Status|NEW |WAITING
> CC| |siddhesh at redhat dot com
> AssignedTo|unassigned at sourceware |siddhesh at redhat dot com
> |dot org |
>
> --- Comment #1 from Siddhesh Poyarekar <siddhesh at redhat dot com> 2013-05-10 08:19:48 UTC ---
> Does this happen with latest master? Changing from fixed iterations to fixed
> time showed such spurious results with bench-modf once (likely because it was
> not rebuilt), which went away when I did a bench-clean and rebuilt it.
>
Now it shows following results. According to them atan is ten times
faster than modf which is clearly wrong.
atan(): ITERS:4.48268e+09: TOTAL:7.79352s, MAX:166.672ns, MIN:0.638ns,
5.7518e+08 iter/s
atan(768bits): ITERS:4.8324e+08: TOTAL:9.83724s, MAX:38.805ns, MIN:17.654ns,
4.91235e+07 iter/s
modf(): ITERS:6.8975e+08: TOTAL:9.53964s, MAX:193.448ns, MIN:4.486ns,
7.23035e+07 iter/s
A following benchmark takes 8.9s which is order of magnitude more than
what benchtest tells.
extern double modf (double, double *);
int main(){ int i;
double x=0;
double ret=0;
double f;
for(i=0;i<1000000000;i++){
ret+=modf(x,&f);
x+=0.1;
}
return ret;
}
--
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.