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Date: Sat, 25 Apr 2015 22:28:31 +0200
From: Agnieszka Bielec <>
Subject: Re: [GSoC] John the Ripper support for PHC finalists

2015-04-25 21:20 GMT+02:00 Solar Designer <>:
> "4 GPU units" sounded weird and confusing to me.
> If you put a hash of a known password in a text file, and put the
> password somewhere down a wordlist, and run "john" with pomelo-opencl
> against that, will it crack the hash?

It works

>I expect it won't, since the code
> looks broken to me.  You don't actually have any test vectors in
> opencl_pomelo_fmt_plug.c, so when you --test you don't actually test,
> right? :-(

no, now I keep  in fmt_tests many hashes with various costs
and it's 100 lines of code. Before I was generating hashes to structure
fmt_test dynamically because it was convenient for me.
this version of code was rather intended for experiments

> I think you should use a vector data type instead of the separate
> work-items, much like the AVX2 code on CPU uses __m256i and doesn't
> rely on the compiler's auto-vectorization.  Granted, auto-vectorization
> is much more common with OpenCL than with C, but you can help the
> compiler by doing a part of it explicitly anyway (and then it'd be the
> compiler's job to combine these narrow SIMD portions into possibly wider
> SIMD that the hardware might need).  I think you need ulong4 there:

sorry, I didn't tested this. I have noticed now that in function H
index_global and index_local are always divisible by 4 so I can use
this with coalescing

> Also, I think you're over-using "unsigned long", such as for loop
> variables.  This may have performance impact on GPUs.  You should prefer
> "uint" except where a wider type is actually needed.

unsigned long is necessary where m_cost is equal to 21 or bigger
I can test if it will increase the speed but I'm sceptic about that

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