Let's use gcc-4.2, not 4.1 -- OpenMP
Stefan Ehmann
shoesoft at gmx.net
Fri Dec 15 07:09:59 PST 2006
On Friday 15 December 2006 14:39, Poul-Henning Kamp wrote:
> In message <200612151250.10033.shoesoft at gmx.net>, Stefan Ehmann writes:
> >Settings/Compiler | gcc-3.4 | gcc-4.1 | gcc-4.2
> >----------------------------+---------+---------+---------
> >-O2 | 13.1bn | 13.8bn | 13.5bn
> >-O2 -funroll-loops | 9.6bn | 9.3bn | 9.2bn
> >-O2 -march=athlon-xp -fun.. | 9.7bn | 10.6bn | 10.7bn
> >-O3 | 11.5bn | 9.5bn | 9.6bn
> >-O3 -funroll-loops | 8.4bn | 9.2bn | 9.4bn
> >-O3 -march=athlon-xp -fun.. | 8.8bn | 10.6bn | 11.1bn
>
> I love benchmarks.
>
> It's great when people benchmark things.
>
> Unfortunately, that is not what you have done, because you have
> not indicated what the standard deviation on your numbers are,
> so they are totally worthless.
I've done 3 runs on an otherwise pretty idle system with a maximum deviation
of maybe 1 million instructions. So I figured that accurately calculating the
standard deviation would overshoot the mark for this primitive test.
IMHO the much weaker point in my benchmark is using a single program and only
instruction count. What I wanted to show is whether gcc4 can still be worse
than gcc34 in some cases.
Sometimes performance counters can vary a lot (I've seen double the
instructions on the p4 machine using papiex). So here are the results for
the "-O3 -funroll-loops" row (using the output of 100 runs). Going on further
seems pretty pointless to me.
Using a 99.7 confidence interval, I get these results:
-O3 -funroll-loops:
gcc-3.4: 8362606323 +/- 440336
gcc-4.1: 9246505378 +/- 531302
gcc-4.2: 9401195544 +/- 784106
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