Date: Sun, 1 Apr 2012 23:02:10 +0300 From: Milen Rangelov <gat3way@...il.com> To: john-dev@...ts.openwall.com Subject: Re: fast hashes on GPU Well, those are profiler stats from my sha256 and sha512 kernels: sha256 (using uint4 vectors): Used GPRs = 36 ALU ops = 1654 sha512 (using uint2 vectors): Used GPRs = 51 ALU ops = 5283 So in fact SHA512 is doing ~3.2x more ALU operations to process 2x less hashes. GPR utilization of 51 badly hampers occupancy as well. On Sun, Apr 1, 2012 at 7:16 AM, Solar Designer <solar@...nwall.com> wrote: > > Yes, I expected that SHA-512 would be less efficient on AMD/ATI GPUs > compared to many other hash types on the same hardware. 10x slower than > SHA-256 is extreme, though. I thought/think that the difference should > be less. > > > On NVidia, situation is somewhat better though. > > Yes, that's my expectation, although it's largely due to other > ("competing") hash types being less efficient there (no rotate and > bitselect anyway). I think the only major reason why SHA-512 may be > more than twice slower than SHA-256 on current Nvidia GPUs is the > increased register pressure. Right? > > As you probably recall, we picked raw SHA-512 (and its salted variants) > for one of the first "fast" hashes to experiment with precisely because > it is on the slower side of the fast hashes and thus should fit in the > current formats interface better. For faster fast hashes, we'll need to > proceed with more invasive changes. > > Alexander > Content of type "text/html" skipped
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