* q8_k_r8: fastest matrix multiplication known to human kind
We get PP-512(LLaMA-3.1-8B) = 370 t/s on a Ryzen-7950X!
* q8_k_r8: AVX2
I was worried that we don't have enough vector registrers on
AVX2, but it looks like it handles it just fine. We get
PP-512(LLaMA-3.1-8B) = 354 t/s on a Ryzen-5975WX.
Slightly slower than the Zen4 version with double the threads,
but still a huge upgrade compared to Q8_0_R4.
* q8_k_r4: NEON
We get PP-512(LLaMA-3.1-8B) = 159.2 t/s.
Compare this to the 128 t/s we have fr Q8_0_R4.
* q8_k_r4: go to signed ints
Why?
* On AVX2 _mm256_maddubs_epi16() may overflow, so we need to
stay within the signed int range and use _mm256_sign_epi8.
Not yet tested on the AVX2 comp, vut expect major slowdown.
* It is almost 10% faster on ARM_NEON. Somehow the veorrq_u8()
needed tto convert from unsigned to signed seems to be extremely
slow on the M2-Max
* We only lose ~0.5% in oerformance on Zen4 (there the exclusive
or that we now use to convert fro signed to unsigned seems to be
much faster than on M2-Max)
* Shutup useless compiler warnings
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Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>
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