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Date: Sun, 21 Apr 2013 14:26:02 +0200
From: magnum <>
Subject: Re: minor raw-sha1-ng pull request

On 21 Apr, 2013, at 1:27 , Solar Designer <> wrote:
> Tavis, magnum -
> On Fri, Apr 19, 2013 at 06:25:50PM -0700, Tavis Ormandy wrote:
>> Thanks for the explanation Magnum, I get similar results! I can restructure
>> cmp_all so it's also omp safe, I sent you a pull request for that. It get's
>> anoter 2000K c/s on my machine.
> Thanks!
> The attached patch replaces the heavy "#pragma omp atomic" with much
> lighter OpenMP reduction for the bitwise OR.  I've checked the OpenMP 2.5
> spec (from 2005) - bitwise OR was already supported in the reduction
> clause, so I think we're good in terms of portability.

This is committed. Unstable branch still has the non-OMP version. Should we merge these changes to it?

> Also, I get better speeds at high thread counts when OMP_SCALE is much
> larger - not the current 32, but 1024 or even 10240.  With 32, there's a
> performance regression when going from 4 to 8 threads on FX-8120.  With
> 1024, there's slight speedup.  With 10240, it's roughly 50M vs. 60M c/s
> for 4 vs. 8 threads.

On Intel I get an overall regression at 10240 (and it makes --test=1 run for 8 seconds). I think I'll bump it to 1024 for now.


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