Date: Wed, 27 Jun 2012 01:35:06 -0700 (PDT) From: deepika dutta <deepikadutta_19@...oo.com> To: "john-dev@...ts.openwall.com" <john-dev@...ts.openwall.com> Subject: Re: mschap-v2 conversion Hi magnum, I dont have any practical experience with bitslicing and i think solar can give better answer for expected speedup with bitslicing. I don't find even in literature somebody giving any figure on how much speedup bitslicing can achieve, I feel it all depends on how much one can optimize. Cheers, Deepika ________________________________ From: magnum <john.magnum@...hmail.com> To: john-dev@...ts.openwall.com Sent: Wednesday, June 27, 2012 5:14 AM Subject: Re: [john-dev] mschap-v2 conversion On 2012-06-26 15:02, Solar Designer wrote: > On Tue, Jun 26, 2012 at 10:06:47AM +0200, magnum wrote: >> Solar may respond much better when he gets some more time. > > I'm sorry, but my opinion is that tuning OpenMP performance with the > current early/experimental bitslicing implementation for this format is > premature. This is my fault, I just noticed she broke OMP and she went off fixing it. Anyway, even if it's not time to really *tune* it, it should definitely not be slower than running one core. > Notice that the speedup from bitslicing without OpenMP is quite low, > compared to what we're seeing for purely DES formats (much higher > speedup there). I guess this might be because of the uses of MD4 and > the conversions to/from bitslice representation, but that does not > explain the low speed for the "many salts" case (the uses of MD4 are in > key setup only). We need to seriously look into this and see what can > be done about it. I presume Deepika is not really interested in this particular format but in bit-slicing, so using SSE2 for MD4 might be out of scope. I could add SSE2 for MD4 at some point if it helps. I just need to understand the context. If we always have 32 or 64 (or 128) keys at a time, it should be a walk in the park. I just know the basic theory of BS. Deepika, what is the expected speedup from just BS (no OMP) if this had been a straight format with no MD4 and stuff involved? If we run 64-bit, we do 64 items at a time, right? But it's not 64x faster of course. How much faster, in general, should it be? magnum Content of type "text/html" skipped
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