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Date: Thu, 06 Nov 2014 07:30:09 +0100
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: Discuss Mask-mode with GPUs and changes required for
 its support.

On 2014-11-05 18:55, Frank Dittrich wrote:
> I think the GPU mask processor should support just a very limited
> functionality, i.e., just '?w' and ranges of characters, and core john
> should preprocess --mask and -1 ... -9 into a mask that the GPU formats
> understand.
> That way, --mask mode can be enhanced without the need to adjust all the
> GPU formats.

I'm sure that is Sayantan's plan. GPU will get preprocessed arrays of 
characters per position, or something like that. Also, I believe CPU 
will still process part of the mask. Eg. if your kernel wants ~250 
million candidates per crypt_all() for a duration of about 100 ms, it 
could load 256K words (produced by wordlist + CPU partial mask) and 
apply the rest of the mask on GPU side, multiplying with yet another 1K. 
In that example, transfer would be 1/1000th compared with CPU-only 
generation.

I think we should normally aim for 100-200ms kernel duration, for many 
reasons.

magnum


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