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Date: Sun, 1 Oct 2017 00:45:18 +0200
From: magnum <>
Subject: Re: OMP vs. OpenCL performance

On 2017-10-01 00:38, magnum wrote:
> On 2017-09-30 18:12, Scott I. Remick wrote:
>> 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

BTW I hope you mean 777 p/s on GPU now. If you get that speed on CPU, 
all bets are off - it's now too fast (LOL). The answer below was in the 
context of your CPU figure of about 13-14 p/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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