Fastest GPU kernels, written from scratch.

Matrix Multiplication

Matrix multiplication of square bf16 matrices, accumulated in fp32.

N=4096
Kernel: 763 TFLOPs
cuBLAS: 716 TFLOPs

N=8192
Kernel: 808 TFLOPs
cuBLAS: 795 TFLOPs

Explanation in https://cudaforfun.substack.com/p/outperforming-cublas-on-h100-a-worklog

To run:

make matmul && out/matmul

Example kernels are in examples/matmul/ and orchestration is in matmul.cu

Sum reduction

We compute sum of $2^{30}$ elements.

To run:

make sum && out/sum

Kernel: 3240.11 GB/s
cub Library: 3193 GB/s

Example kernels are in sum.cu