computes the eigenvalues of a symmetric tridiagonal

* matrix T. The user may ask for all eigenvalues, all eigenvalues

in the half-open interval (VL, VU], or the IL-th through IU-th eigenvalues.-computes the eigenvalues of a symmetric tr idiagonal * matrix T. The user may ask for all eig envalues. all eigenvalues in the half-open interval (VL. VU], or the IL-th through IU-th eigenvalues.