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Message-ID: <CA+TsHUAJV9uObumAvtHWV0=N8gS68EYeXz5wZyJMZgotTdzjEw@mail.gmail.com>
Date: Thu, 10 May 2012 03:55:25 +0530
From: SAYANTAN DATTA <std2048@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Sayantan: Weekly Report #3
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.
>
> Well it's not MD4 alone which consumes cpu time. A deeper look into the
code suggests that conversion from byte to hexstring consumes significant
amount of time, nearly around 90% of total CPU time. Thus the remaining
10% of cpu time is consumed by the md4 and other stuffs.
Sayantan.
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