MatMul Benchmark

Run:

FC=gfortran cmake -DMATMUL_BLAS=OpenBLAS .
make
OMP_NUM_THREADS=1 ./matmul

Benchmark results on Apple M1

The theoretical performance peak for matmul is just the cost of fma, which is 0.125 clock cycles per double precision matrix element (fmla.2d v0, v0, v0 takes 0.25 cycles), and 0.0625 per single precision element.

Single precison (f32) matmul

peak = 0.0625 clock cycles

n    OpenBlas
512  0.0768
1024 0.0672
2048 0.0640
4096 0.0632
8192 0.0631

To convert these clock cycles to seconds, multiply by n^3 and divide by 3.2GHz. For example the n=8192 case gives 10.84s:

>>> n = 8192; 0.0631*n**3 / 3.2e9
10.840497455104