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Date: Tue, 16 Jun 2015 17:06:40 +0300
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: bcrypt-opencl local vs. private memory

On Sat, May 09, 2015 at 04:21:25PM +0530, Sayantan Datta wrote:
> On Fri, May 8, 2015 at 1:22 AM, Solar Designer <solar@...nwall.com> wrote:
> 
> > Will you take this task from here, please?
> 
> Yes, of course. I'll look into it.

Thanks!

Sayantan took care of this at the time, in commit
97545b7ab51a4e8ddccba1a098f5448d808ae39b which includes:

#if gpu_nvidia(DEVICE_INFO)
#define MAYBE_LOCAL             __private
#else
#define MAYBE_LOCAL             __local
#endif

I've just tested this on our GTX 570 as well, and unfortunately it
actually hurts performance there.  (Even though it was helping on our
TITAN a bit.)  With the above commit, I am getting around 400 c/s.
With forced use of __local, it's around 1200 c/s.

I merely want to document this in here.  I am not suggesting making any
further change yet.  Either of these speeds is quite low anyway.

I am currently discussing bcrypt on GPU with Alain (via off-list
e-mail), who managed to achieve much higher speeds anyway, including on
his GTX 590 (per GPU).

Alexander

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