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Message-ID: <20111107022422.GA22695@openwall.com>
Date: Mon, 7 Nov 2011 06:24:22 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: comparing two benchmarks
On Mon, Nov 07, 2011 at 05:50:24AM +0400, Solar Designer wrote:
> $ ./relbench.pl asis Os
> Geometric mean of 158: 0.914688 real, 0.915206 virtual
> Standard deviation: 0.966662 real, 0.962432 virtual
>
> Thus, it appears that going from -O2 to -Os made things slower by 8.5%
> overall. However, the standard deviation is large, meaning that things
> vary between individual benchmarks a lot.
While it is true that the standard deviation is relatively large on this
test, it is not as large as shown above - there was a bug in the script.
To correct it, right before these lines:
> $dr **= 0.5;
> $dv **= 0.5;
add:
$dr /= $n;
$dv /= $n;
Then we get:
$ ./relbench.pl asis Os
Geometric mean of 158: 0.914688 real, 0.915206 virtual
Standard deviation: 0.076904 real, 0.076567 virtual
For comparison, the standard deviation for equivalent benchmarks is
much lower:
$ ./relbench.pl asis asis-2
Geometric mean of 158: 1.000566 real, 1.002138 virtual
Standard deviation: 0.013746 real, 0.013566 virtual
$ ./relbench.pl Os Os-2
Geometric mean of 158: 1.002091 real, 1.001839 virtual
Standard deviation: 0.008966 real, 0.008853 virtual
Alexander
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