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Date: Tue, 14 Feb 2012 20:40:41 +0400
From: Solar Designer <>
Subject: Re: OMP version not use all CPU

On Tue, Feb 14, 2012 at 08:19:53AM -0800, Alain Espinosa wrote:
> On 2/14/12, Solar Designer <> wrote:
> > What hash type(s) are you testing on?  Of those you provided benchmarks
> > for here: only LM and MSCash
> > hashes include OpenMP parallelization in JtR currently, but NTLM don't.
> I try LM, MSCASH and NTLM. I do not know NTLM do not have OpenMP support.

How do you know it uses just one thread?

For LM hashes, the parallelization efficiency is in fact very poor,
especially on Windows.  So I am not surprised if there's almost no speed
increase or even a speed decrease with more threads, and you could try
just 2 threads first (4 might be slower than 2).

> > Can you try the non-jumbo 1.7.9 as well (also john-omp.exe)?
> Will do and i report back.

Thanks.  I've just confirmed that john-omp.exe in does
indeed include OpenMP support for LM hashes, though.

> > Oh, and the speed you're reporting for LM hashes (25M c/s) is
> > surprisingly low for JtR 1.7.9 on a modern CPU.  As you can see, we have
> > higher speeds for 1.7.9 here:
> I take a look at this numbers. One difference its that i use a laptop
> CPU, other its that i perform a "real" benchmark and not the "-test"
> option. I consistently found differences in "-test" option and "real"
> crack speed. I will test the "-test" option and review the method i
> use to gather performance data.

Yes, incremental mode introduces some measurable overhead for fast
hashes like this.  I need to introduce a dumber mode for benchmarking
and for exhaustive searches.

Also, we only have 32-bit builds for Windows now, whereas many of the
faster benchmarks are for 64-bit builds (mostly on Linux).

For 1 thread benchmarks (as reported on the Hash Suite website), are you
using john.exe or john-omp.exe (limited to 1 thread)?  Naturally, I'd
prefer the former. ;-)


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