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Date: Thu, 10 May 2012 01:50:58 +0400
From: Solar Designer <>
Subject: Re: Sayantan: Weekly Report #3

Sayantan -

On Thu, May 10, 2012 at 02:46:58AM +0530, SAYANTAN DATTA wrote:
> Thanks. Done.

(regarding loop unrolling)

Thanks.  I'll take a look once this is in magnum-jumbo.

> On Thu, May 10, 2012 at 12:02 AM, Solar Designer <> wrote:
> > Oh, do you mean that the on-CPU portion of MSCash2, which we're
> > executing sequentially with the on-GPU code (not in parallel yet), was
> > consuming a substantial portion of total time?
> Yes. It consumed around 20% of the total time.

Wow.  20% is excessive and not expected.  We need to figure out why this
is so - or maybe it is not (that is, part of the speedup might be from
some side-effect, not directly from the OpenMP parallelization).

You compute two MD4 hashes on host per MSCash2 hash, correct?  At 80k c/s,
this means you compute 160k MD4s per second, and you say this corresponds
to over 20% of total running time (you say you saved 20% by
parallelizing this).  Thus, the total speed would be less than 800k MD4/s -
sounds too low even for the somewhat non-optimal and non-vectorized code
that we have there.  For the raw-md4 format in a "make generic" build
(thus also non-vectorized), I am getting between 5M and 6M c/s on this CPU
(also on one core, indeed).  (For vectorized code, it's more like 30M c/s
on one core.)  So there's a factor of 7 difference here, which we don't
have an explanation for.

> BTW GTX 570 performance has been also improved to 25k c/s with OMP.

...and what was it for the same code revision, but without OpenMP?

> Also changed the file name from opencl_MSCASH2_fmt.c to
> opencl_mscash2_fmt.c as requested by Lukas.

Yes, thanks.  That uppercase was weird.


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