Date: Mon, 30 Mar 2015 13:38:51 +0300 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: [GSoC] John the Ripper support for PHC finalists On Mon, Mar 30, 2015 at 12:17:25PM +0200, magnum wrote: > On 2015-03-30 12:02, Solar Designer wrote: > > On Mon, Mar 30, 2015 at 10:24:45AM +0300, Solar Designer wrote: > >> So the speed of C code is maybe good - I say maybe because we don't know > >> yet how much better it can be made. One of two OpenCL SDKs running on > >> the CPUs achieves about the same speed, which is a good sanity check. > >> The other fails to vectorize the code, resulting in much lower speed. > > > > Actually, the failure to vectorize is possibly a red herring. POMELO is > > designed to be somewhat SIMD-unfriendly, Actually, POMELO v2 includes 256-bit SIMD parallelism (v1 did not). This is sufficient for current CPUs. POMELO v2 still tries to discourage SIMD wider than that. > > including in attack > > implementations (with extra parallelism from having multiple candidate > > passwords). So I doubt the other OpenCL SDK vectorized it; perhaps it > > just didn't print the warning. This needs to be looked into for real. > > AMD's CPU driver never prints such warnings, and it never reports > succesful auto-vectorization either. Actually I'm not convinced it does > auto-vectorizing at all. I have a few formats that adopt to the device's > reported "best vector width" with pre-vectorized code and the AMD driver > usually respond very well to that iirc. > > Anyway the speed difference is almost 15x, that wouldn't be explained > with vectorizing alone. Right. Alexander
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