The EISPACK eigensystem package as documented in the first edition of this guide has expanded in both depth and breadth in its second release. A set of subroutines affording additional variants for the six problem classes encompassed in the first release has been added. Another set of additional subroutines has extended the applicability of EISPACK to new problem classes; prominent among these are the real symmetric band standard eigenproblem, the symmetric and non-symmetric real generalized eigenproblems, and the singular value decomposition of an arbitrary matrix.
Read more at http://ebookee.org/Matrix-Eigensystem-routines-EISPACK-guide_1132163.html#CMjCw0qytgshlQ0b.99