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Date: Mon, 31 Aug 2020 20:01:22 -0400
From: Rich Rumble <richrumble@...il.com>
To: john-users@...ts.openwall.com
Subject: Re: SIMD performance impact

On Mon, Aug 31, 2020 at 5:09 PM Vincent <spam@...lab.nl> wrote:

> Hi,
>
> John can use instruction set specific optimizations to fully exploit
> technology like SIMD. I haven't got CPUs that support AVX-512 but I'm
> very interested in the possible performance gains. So my question is:
> can someone with the latest generation CPU run a 'john --test' with
> different instruction set binaries (for example SSE4.2, AVX, AVX2,
> AVX-512) on the same CPU?
>
You may find some of what you're after on the WIKI, not only in terms of
instructions optimizations, but threading as well as parallel/workload
splitting methods like MPI, HT and thread count. You could certainly force
JtR to build and favor those instructions, but I think by default it tries
to optimize on what is detected with ./configure and when built too I
believe it will try to figure out what is present.
https://openwall.info/wiki/john/benchmarks
I remember when JtR started using MMX and then SSE (can't remember which
came first) and I thought it was genius! With AMD (Ryzen etc...) I'm
curious myself to see how the threadrippers do vs Intel ;)

> I think it might also be interesting to match current Intel (Core i9 &
> Xeon) and AMD (Ryzen & Epyc) processors to see what the impact of
> implementation details is (like Xeon AVX-512 versus Epyc AVX2).
>
> Perhaps interesting to upgrade
> <https://openwall.info/wiki/john/benchmarks> with all algorithms (since
> some do not seem to be SIMD-accelerated) and with results based on
> different instruction sets on the same CPU?
>
> Thanks!
>
> Cheers, V
>

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