Using current implementations and current hardware, the DMRG algorithm for optimizing a multiconfigurational wave function of the matrix product type becomes unaffordable due to computational complexity and memory limitations after about 100 orbitals. Twostep diagonalization approaches such as LASSIS could in principle handle much larger systems than this, because they systematically eliminate whole sectors of the complete active space which are not physically relevant but which must be explored by the DMRG algorithm.