ssterf(3F)

NAME
     SSTERF - compute all eigenvalues of a symmetric tridiagonal matrix using
     the Pal-Walker-Kahan variant of the QL or QR algorithm

SYNOPSIS
     SUBROUTINE SSTERF( N, D, E, INFO )

         INTEGER        INFO, N

         REAL           D( * ), E( * )

PURPOSE
     SSTERF computes all eigenvalues of a symmetric tridiagonal matrix using
     the Pal-Walker-Kahan variant of the QL or QR algorithm.


ARGUMENTS
     N       (input) INTEGER
             The order of the matrix.  N >= 0.

     D       (input/output) REAL array, dimension (N)
             On entry, the n diagonal elements of the tridiagonal matrix.  On
             exit, if INFO = 0, the eigenvalues in ascending order.

     E       (input/output) REAL array, dimension (N-1)
             On entry, the (n-1) subdiagonal elements of the tridiagonal
             matrix.  On exit, E has been destroyed.

     INFO    (output) INTEGER
             = 0:  successful exit
             < 0:  if INFO = -i, the i-th argument had an illegal value
             > 0:  the algorithm failed to find all of the eigenvalues in a
             total of 30*N iterations; if INFO = i, then i elements of E have
             not converged to zero.