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!
how to use lanczos code from netlib for large sparse symmetric matrix?
eigensystem;fortran;lapack;banded matrix