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Date: Tue, 5 May 2015 07:49:13 +0300
From: Shinnok <admin@...nnok.com>
To: john-dev@...ts.openwall.com
Subject: Re: [Johnny] Task 1.4.2 fork and OpenMP


> On May 4, 2015, at 3:47 AM, Mathieu Laprise <mathlaprise@...il.com> wrote:
> 
> On a different note, for OpenMP, I'm understanding that it's not a command line option, it's something that you have to change in the makefile when you compile. I guess that it would work AS IS in Johnny. Can we take a decision about this discussion between frank and shinnok ? Do you want the user to specify a different number of openmp threads or keep it simple for him(default, number of logical cores) ?
> > Aleksey, Frank, is it my understanding that OpenMP is handled via
> > environment args? In this case, what exactly does Johnny need to support
> > in regards to that? (OMP_NUM_THREADS?)
> 
> If you don't pass OMP_NUM_THREADS, the default will be the number of
> logical cores. Not sure if you really want the user to specify a
> different number. This could be useful if there is other load on the system.
> 
> 

I think I remember reading in a separate e-mail(which I can't seem to locate right now) that it might be useful to have fine-grained thread control per process for specific hw setups and/or cipher algorithms. There's also a clear advantage or disadvantage for some ciphers under JtR when being tested in fork vs omp scenarios.

Let's make it a dropdown similar to fork. Use QProcessEnvironment to pass the preference to JtR as depicted here:
http://doc.qt.io/qt-5.4/qprocess.html#setProcessEnvironment

We don't "care" if JtR supports OMP or not at this point. Setting that env var won't hurt non-omp builds.

Add both options to a new category inside a QGroupBox labeled Parallelization at the end of the current Options page.

Thanks,
Shinnok
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