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Date: Sat, 11 Aug 2012 01:59:14 +0200
From: Lukas Odzioba <>
Subject: Re: Current -fixes GPU formats vs TS

2012/8/11 Solar Designer <>:
> In trying to trigger the problem without running xsha512-cuda first, I
> added:
>         cudaMemset(cuda_hash, -1, PWSAFE_OUT_SIZE);
> right after:
>         cudaMalloc(&cuda_hash, PWSAFE_OUT_SIZE);
> This didn't make any difference in triggering the problem (nor in
> preventing it), but surprisingly it provided a 3% speedup (approx.
> 106k c/s to 109k c/s on bull's GTX 570).
> A memset with 0 also provides some speedup (a slightly smaller speedup?
> not sure).
> Any idea why?  This might be a clue.

I wasn't able to reproduce this bug that way (running xsha first) but
it I was able to get 100% self test fails during ./john -test=0.
This speedup is weird what is c/s, 3% seems to be more than error
dispersion. I have no idea what is the source of this speedup. Maybe
some powersaving mechanisms inside cuda impelentation or device

On gtx470 I get 466->470 after adding memset.


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