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Date: Tue, 25 Aug 2015 08:50:58 +0300
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: md5crypt-opencl

On Mon, Aug 24, 2015 at 07:57:20PM +0200, magnum wrote:
> On 2015-08-24 11:38, Solar Designer wrote:
> >With the inline ptx asm enabled (need proper compile-time check for it):
> >
> >Raw:    1664K c/s real, 1664K c/s virtual
> 
> I added a proper check in 7531c0b, although it's starting to go south - 
> I think we should actually export the major/minor numbers to macros 
> instead of defining functions for specific sm_xx combinations. But 
> anyway it works correctly right now.

Confirmed, thanks!

Testing this further, I notice that our LWS/GWS tuning which tries
powers of 2 only is highly non-optimal for this card.  Simply adjusting
LWS and GWS, I get much better results than the above:

[solar@...er run]$ LWS=96 GWS=129024 ./john -test -form=md5crypt-opencl -dev=5 
Device 5: GeForce GTX TITAN
Benchmarking: md5crypt-opencl, crypt(3) $1$ [MD5 OpenCL]... DONE
Raw:    1984K c/s real, 1984K c/s virtual

and actual cracking:

[solar@...er run]$ LWS=96 GWS=129024 ./john -form=md5crypt-opencl 6.md5crypt.pw -dev=5 -mask='?l?l?l?l?l?l?l?l'
[...]
0g 0:00:02:03  0g/s 0p/s 2395Kc/s 2395KC/s GPU:76б╟C util:99% fan:50% aaaaaaaa..lwihaaaa

(was ~1850K before)

Also, GWS=129024 is actually much lower than what was auto-tuned (512K),
which is helpful for small wordlist runs and to reduce the amount of work
lost on interrupt/restore.  In fact, seeing how low we can get:

[solar@...er run]$ LWS=96 GWS=16128 ./john -test -form=md5crypt-opencl -dev=5
Device 5: GeForce GTX TITAN
Benchmarking: md5crypt-opencl, crypt(3) $1$ [MD5 OpenCL]... DONE
Raw:    1756K c/s real, 1774K c/s virtual

This is suboptimal, but still better than our auto-tuning - and that's
~32.5 times lower than the auto-tuned GWS, so has much better usability
for quick runs.

Alexander

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