Benchmarking nested do loops, MATMUL and Blas DGEMM

The M1 and M2 also have a matrix coprocessor (a special matrix acceleration unit): GitHub - corsix/amx: Apple AMX Instruction Set · GitHub. In newer chips (M4 and later?) they upgraded this to the Arm SME extension.

In the past I did some benchmarking of the BLAS Level 3 dtrsm routine; in the plot below label

dtrsm

is for Apple Accelerate and the rest are variants written by GitHub Copilot, some with explicit vectorization using NEON intrinsics:Accelerate is the fastest. Notice the the big jumps when the matrix size is a multiple of 8? I believe that’s the AMX extension.