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Date: Wed, 5 Jun 2013 05:08:18 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: bcrypt-opencl

On Tue, Jun 04, 2013 at 09:56:26AM +0530, Sayantan Datta wrote:
> There was a problem with loop unroll(automatically done by compiler). So I
> unrolled it manually. This kind of problem is very common with AMD's
> opencl. It generally happens with for loops with smaller loop count.
> Compiler doesn't unroll properly when the unroll is a bit complicated.

OK.  Thank you for working around this problem.

> Another concern is that the kernel is spilling registers, which it
> shouldn't. This is lowering the performance too. Most likely the P box is
> spilling.
> 
> Device 1: Tahiti (AMD Radeon HD 7900 Series)
> Optimal Global Work Size:1024
> Benchmarking: bcrypt-opencl ("$2a$05", 32 iterations) [Blowfish OpenCL]...
> DONE
> Raw:    3960 c/s real, 179200 c/s virtual

Yeah.  This is a slight performance regression compared to what we had
with Catalyst 12.8 - IIRC, the speed was 4200+ c/s.  It'd be nice if you
manage to avoid the register spilling.  Thanks!

Alexander

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