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Date: Sat, 22 Sep 2012 01:41:44 +0530
From: Sayantan Datta <std2048@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: bitslice DES on GPU

On Sat, Sep 22, 2012 at 12:51 AM, Solar Designer <solar@...nwall.com> wrote:

> Hi Sayantan,
>
> On Sat, Sep 22, 2012 at 12:31:26AM +0530, Sayantan Datta wrote:
> > I was experimenting with DES_BS_EXPAND set to 0 and using different types
> > of memory .
> >
> > 1. B[] in local memory and K[] in private register space:
> > With this combination I'm getting speeds of around 24M c/s on 7970 and 5M
> > c/s on 570.
> >
> > 2. B[] in private register space and K[] in local memory
> > I'm getting 12M c/s on 570 while I couldn't get it working on 7970.
> Getting
> > hash fails every time. Most likely the problem is with referencing B[]
> > array in z(p) macro.
>
> That's curious.  Even more interesting would be speed numbers with the
> overhead mostly excluded - that is, use this test vector:
>
>         {"..X8NBuQ4l6uQ", ""},
>
> set the iteration count e.g. to 2501 (any odd value should do), and
> multiply the reported c/s rate by 100 (if you picked 2501) to get the
> descrypt equivalent cracking speed.
>
> As to the overhead, we'll need to deal with it by other means later.
>
> I just did some math, and I think that your 24M with overhead may
> correspond to around 65M in the without-overhead test.  Please confirm
> or disprove. ;-)
>
> 1/(1/39+1/41) = 19.99
>
> 1/(1/39+1/60) = 23.64
> 1/(1/39+1/65) = 24.38
>
> 39M is my guess as to the "overhead speed" alone (without crypto), based
> on the 19.9M "with overhead" speed you reported and my 41M
> without-overhead test.  Assuming that this "with overhead" speed
> remained the same, it'd take around 65M without-overhead speed to
> reach/exceed 24M reported for overhead+crypto.
>
> Thanks,
>
> Alexander
>

Hi Alexander,

In the previous test Global no. of work items were half of this time. So
the overhead is double in this test than the last one.
Setting 2501 I'm getting 35M without any overhead. So your guess of 65M is
accurate.

here's the math:

1/(1/(39x2) +1/65) =35.4

Regards,
Sayantan

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