proc gemm_nn_fallback[T](m, n, k: int; alpha: T; A: seq[T]; offA: int;
                         incRowA, incColA: int; B: seq[T]; offB: int;
                         incRowB, incColB: int; beta: T; C: var seq[T];
                         offC: int; incRowC, incColc: int)