I have an university project that involves the diagonalization of large sparse matrices, I decided to use Fortran and I'm using ifx intel fortran compiler with mkl lapack interface. The project requires to use Lanczos or similar algorithms, so I'm using mkl_sparse_d_ev, where the input variable pm is set to use Krylov-Schur method.
What is not clear is how to set the first vector for generating the Krylov subspace, it looks like the implementation always use a random one, I cannot find that information anywhere, but is essential in the algorithm that I'm implementing, can someone help me? Or at least suggest other routines suited for the problem?