how to use lanczos code from netlib for large sparse symmetric matrix?

I want to use lanczos method to calculate the few lowest eigenvalue and eigen-vector of a large sparse symmetric matrix(~50k x ~50k). In http://www.netlib.org/lanczos/index.html I found the codes leval and levec are suitable for my situation. However, the instruction is too complicated to find how to use it and I don't know how to set the input and output files. Who used it and please gives some advice. Thanks!

• What programming language do you want to use? – Lagerbaer Oct 16 '13 at 16:43
• @lagerbaer i am using fortran90... – mpk Oct 18 '13 at 5:25

This does not directly answer your question, but maybe you want to use something like ARPACK, for example scipy.sparse.linalg.eigsh in python.