Add AVX512 implementation of GEMM - Q4_Kx8

[Srihari-mcw]

• The PR contains AVX512 version of ggml_gemm_q4_K_8x8_q8_K introduced in Block interleaving support for Q4_K quantization for x86 AVX2 architecture #12332
• Good gains were seen with prompt processing with the above changes compared to the AVX2 version

GCC Linux :

Q4_K_M Model :

model	size	params	backend	threads	test	t/s	speedup	Commit id
llama 7B Q4_K_M	3.80 GiB	6.74 B	CPU	6	pp 512	66.83 ± 0.10		3f9da22 - Base Commit
llama 7B Q4_K_M	3.80 GiB	6.74 B	CPU	6	pp 512	84.00 ± 0.15	25.70%	559b050 - Updated Commit
llama 7B Q4_K_M	3.80 GiB	6.74 B	CPU	6	tg 128	14.02 ± 0.00		3f9da22 - Base Commit
llama 7B Q4_K_M	3.80 GiB	6.74 B	CPU	6	tg 128	14.01 ± 0.00	-0.07%	559b050 - Updated Commit

Q4_K_S Model :

model	size	params	backend	threads	test	t/s	speedup	Commit id
llama 7B Q4_K_S	3.59 GiB	6.74 B	CPU	6	pp 512	73.66 ± 0.23		3f9da22 - Base Commit
llama 7B Q4_K_S	3.59 GiB	6.74 B	CPU	6	pp 512	98.35 ± 0.27	33.52%	559b050 - Updated Commit
llama 7B Q4_K_S	3.59 GiB	6.74 B	CPU	6	tg 128	14.78 ± 0.00		3f9da22 - Base Commit
llama 7B Q4_K_S	3.59 GiB	6.74 B	CPU	6	tg 128	14.77 ± 0.00	-0.10%	559b050 - Updated Commit

GCC Version = 12.3

The models were quantized and tested from meta-llama2 7B model - https://huggingface.co/meta-llama/Llama-2-7b

The PR was tested in AMD Granite Ridge 9600X which supports the following flags by default :

system_info: n_threads = 6 (n_threads_batch = 6) / 12 | CPU : SSE3 = 1 | SSSE3 = 1 | AVX = 1 | AVX_VNNI = 1 | AVX2 = 1 | F16C = 1 | FMA = 1 | BMI2 = 1 | AVX512 = 1 | AVX512_VBMI = 1 | AVX512_VNNI = 1 | AVX512_BF16 = 1 | LLAMAFILE = 1 | OPENMP = 1 | AARCH64_REPACK = 1 |

Further the perplexity was tested and found to be similar with the Q4_K_S model :

The perplexity results are tabulated as follows :

model	perplexity (Final estimate PPL)	Commit id
llama 7B Q4_K_S	5.8887 +/- 0.03281	3f9da22 - Base Commit
llama 7B Q4_K_S	5.8887 +/- 0.03281	559b050 - Updated Commit

[Nor7th]

Hi, may I ask how to test the correctness of such kernel optimization? Saying, is there a way to test whether the result of gemm/gemv by the simd implementation is correct?

[Srihari-mcw]

@Nor7th , we initially go with comparing the individual output values of GEMM and GEMV for with the mul mat outputs earlier without introduction of changes. Once there is sufficient evidence that there is not much divergence in the values, we take the perplexity measure as documented above.

Further, if there is not even precision differences observed, the llama-cli output tends to be the same. For example with the AVX2 and AVX512 Outputs in this function targeted for optimization, the output remains the same for different prompts and seeds. Thanks