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Date: Tue, 1 Sep 2020 11:48:02 +0200
From: Vincent <>
Subject: Re: SIMD performance impact

On 01/09/2020 02:01, Rich Rumble wrote:
> On Mon, Aug 31, 2020 at 5:09 PM Vincent 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.

For sure it's possible. So I would be interested in a:

cd $john/src/
for simd in sse4.2 avx avx2 avx512f avx512bw
	./configure --enable-simd=$simd
	make -s clean
	make -s
	echo "$simd"
	../run/john --test

I just haven't got the latest and greatest AMD and Intel CPUs to run it 
myself ;)

Central documentation would be a big plus for others I guess, for future 
users with similar questions.

Cheers, V

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