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Message-ID: <20120324014011.GB5676@openwall.com>
Date: Sat, 24 Mar 2012 05:40:11 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: Possible improvement of cryptsha256-cuda
Hi myrice,
On Fri, Mar 23, 2012 at 09:23:48PM +0800, myrice wrote:
> Lukas, I am reading your cryptsha256-cuda code. The cuda output buffer is
> not coalesce accessed. That is(in file cuda/cryptsha256.cu):
> 284#pragma unroll 8
>
> 285 for (i = 0; i < 8; i++)
>
> 286 tresult[hash_addr(i, idx)] = alt_result[i];
> The hash_addr is:
> #define hash_addr(j,idx) (((j)*(KEYS_PER_CRYPT))+(idx))
>
> However, the access pattern is not regular. That means we will access 0
> 2000 4000. And each access need a large memory cycles. In cuda
> 4.1 profiler. It also says that the global memory store is very
> inefficiency. I think we could change it to idx*8+i. And make an address
> translate in cpu side. I am doing this!
Thank you for posting and for working on this! What you're doing is in
line with my suggestions to Sayantan, which I've just posted. :-)
Alexander
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