Date: Tue, 3 Apr 2012 20:09:27 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: fast hashes on GPU myrice - On Tue, Apr 03, 2012 at 10:34:48PM +0800, myrice wrote: > 1) In real crack, it seems that the second time we saw a previous salt, > we receive all salts in the file(Just as shadow file). Is this right? Yes. > 2) In benchmark, we only use two salts in fmt_test struct. With many salts, > we repeat use first two (or one) salts for 0x100(256) times. Yes. We use two unless there's only one provided in the tests. > So if we see > the same salt second time, we cannot do bulk hashing.I am still thinking > for it. Any ideas? Yes, this is something I had overlooked when suggesting this approach to you. Well, actually you can do the bulk hashing there and you'll even have correct results - but you'll only do it for two salts, which is not exactly "many", so the benchmark result won't be very meaningful. You may revise the condition to be keys_changed && saw_same_salt_again. (keys_changed is set in set_key() as we discussed before.) This condition will be true only after bench_set_keys() has been called for a second time, so by that point you'll have the correct number of salts recorded (including duplicate salts, which are present in benchmarking only). Anyway, as I wrote to you earlier today, I don't expect any of this to result in much speedup (assuming correctly tuned max_keys_per_crypt in either case). Instead, you may focus on offloading hash comparisons to GPU. > I tested new code on GTX580(THREADS 480, BLOCKS 1024): You could try THREADS 512 there. > Benchmarking: Mac OS X 10.7+ salted SHA-512 CUDA [64/32]... DONE I suggest that you put "CUDA" in place of "64/32", and remove " CUDA" from "Mac OS X 10.7+ salted SHA-512 CUDA". The bits_used/bits_total notation was never meant to include let's say bits_desired in the bits_used portion. ;-) > Many salts: 34065K c/s real, 34065K c/s virtual > Only one salt: 23359K c/s real, 23130K c/s virtual That's a bit slower than what I had on GTX 570 o/c (which should be of similar speed to a GTX 580 at stock clocks). I think some of the other optimizations/hacks I was making is not yet in your code. I'll test your newer code and see. Thanks, Alexander
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