I wasn't in a position to make realistic comparisons on SKX at the time, but it seems that Zen is similar to Haswell (and Haswell/Broadwell is still pretty rele

I wasn't in a position to make realistic comparisons on SKX at the time, but it seems that Zen is similar to Haswell (and Haswell/Broadwell is still pretty relevant in HPC). I'll eventually get back to it and try on SKX. I expect you can do better with the generic code, as suggested. The point is that received wisdom is that you can't just rely on compiler vectorization but need careful hand-(un?!)rolled code. The story around BLIS was that GCC wouldn't vectorize loops that at least GCC6 actually does (better than the SSE3 code in the how-to-optimize-dgemm tutorial). Then the suggestion was to force it with the OpenMP simd pragma, which is worse on Haswell because it doesn't use fma, but I don't know if that's relevant for, say, POWER using the generic kernels. I'm not actually ignoring level 1 and 2, although my interest is HPC. BLIS' reduction-type loops in generic C at least get vectorized now via -funsafe-math-optimizations. Small dgemm is important in some HPC applications too, for which BLIS doesn't do too well, but there's libxsmm.