Date: Sun, 15 Mar 2015 01:02:55 +0300 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: interleaved bitslice? On Sat, Mar 14, 2015 at 10:49:30PM +0100, magnum wrote: > On 2015-03-14 20:01, Solar Designer wrote: > > On Thu, Mar 12, 2015 at 08:37:01AM +0100, magnum wrote: > >> On 2015-03-11 21:55, Solar Designer wrote: > >>> solar@...l:~/md5slice$ gcc md5slice.c -o md5slice -Wall -s -O3 -fomit-frame-pointer -funroll-loops -DVECTOR -march=native > >>> > >>> This gave "warning: always_inline function might not be inlinable" about > >>> FF(), I(), H(), F(), add32r(), add32c(), add32() - but then it built > >>> fine. The speed is: > >> > >> Solar, > >> > >> While experimenting with this I noticed using a vector size of 32 but > >> still compiling for AVX gave a slight boost (~5%). I assume this ends up > >> similar to the interleaving we use in Jumbo, and is faster for the same > >> reasons. > > > > I've just tested this with gcc 4.9.2 on Linux, and the generated code is > > "floating-point" 256-bit AVX. So this is not interleaving. > > And yet it's faster? I would not have guessed that ever but I suppose > it's not that special. I'm probably the guy least using floating point > in the entire world. Like I mentioned, 128-bit vs. 256-bit AVX is roughly same speed per-bit on current CPUs, for bitslice DES at least. So your 5% speed difference, in either direction, is realistic. We should really try 256-bit AVX2 on the bitslice DES code. It might be way faster on Haswell, based on other benchmarks so far. Alexander
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