GFortran maintainer here. Please don&#x27;t judge GFortran by the speed of the MATMUL intrinsic. The matmul implementation is really a bare-bones unoptimized version. If you want performance use the -fexternal-blas option and link in a tuned BLAS library such as MKL or OpenBLAS. The exception is if you have very small fixed-size matrices, then the code is inlined and should be faster than BLAS.