ssterf(3)

NAME

SSTERF - compute all eigenvalues of a symmetric tridiago

nal matrix using the Pal-Walker-Kahan variant of the QL or QR al

gorithm

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 algo

rithm.

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 tridiago

nal 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 ille

gal 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.

LAPACK version 3.0 15 June 2000

SSTERF(3)