This portable, modular Fortran 90 software package implements the thick-restart
Lanczos method, for use with real symmetric or complex Hermitian eigenvalue
problems where a small number of eigevalues and eigenvectors are needed, and
the matrices involved may be too large to store in computer memory. Most of
the arithmetic computations in the software are done through calls to BLAS
and LAPACK.  The software can be instructed to write checkpoint files so that
it can be restarted is a later time.

WWW: http://crd.lbl.gov/~kewu/trlan.html