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Date: Sun, 1 Oct 2017 00:38:17 +0200
From: magnum <>
Subject: Re: OMP vs. OpenCL performance

On 2017-09-30 18:12, Scott I. Remick wrote:
> On 09/29/2017 09:44 AM, Frank Dittrich wrote:
>> Actually, john will provide that information :
> Ok here what I had gotten:
> ~/JohnTheRipper/run$ ./john --session=opencl 
> --format=PBKDF2-HMAC-SHA512-opencl hash.txt
> Device 0: GeForce GTX 750
> Using default input encoding: UTF-8
> Loaded 1 password hash (PBKDF2-HMAC-SHA512-opencl, GRUB2 / OS X 10.8+ 
> [PBKDF2-SHA512 OpenCL])
> Cost 1 (iteration count) is 48543 for all loaded hashes
> So if the "48543" is what you thought would need to be over 500K to 
> account for the speed, then I suppose maybe there is indeed a 
> problem...? Currently been running 1 day, 13h, on phase 3/3 and 777p/s

One (or some) of the format's test vectors have an iteration count of 
10000. You can benchmark it like this:

$ ../run/john -test -form:PBKDF2-HMAC-SHA512 -cost:10000
Will run 8 OpenMP threads
Benchmarking: PBKDF2-HMAC-SHA512, GRUB2 / OS X 10.8+ [PBKDF2-SHA512 
128/128 AVX 2x]... (8xOMP) DONE
Speed for cost 1 (iteration count) of 10000
Raw:	721 c/s real, 96.2 c/s virtual

The figure above is from a 5 yo laptop w/ 4 cores 8 threads and clocked 
at a relaxed 2.3 GHz. Unless I'm totally senile right now, that should 
mean a figure of about 148 c/s for 48583 iterations and you only only 
get a tenth of that? I have no idea why (unless your gear is also 
occupied with computing other things).

Try that exact benchmark and report your outcome. The system should be 
idle when benchmarking, of course.


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