Fortran intrinsic functions v.s. mkl functions or subroutines

Hi all,

I am wondering  which I should  use in my code, for example if I do matrix multiplication A(100,100)*B(100,100), matmul(A,B) or gemm()?

The same uncertainty for other functions, e.g. dot_product, and those VML functions, e.g. exp(A)  v.s. vsexp().

Let's ignore parallelization, because mostly I do these operations for each openmp thread.

Thank you.

Benqiang