NAME

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

SYNOPSIS

SUBROUTINE DSTERF(
N, D, E, INFO )

INTEGER INFO, N

DOUBLE PRECISION D( ∗ ), E( ∗ )

PURPOSE

DSTERF 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) DOUBLE PRECISION 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) DOUBLE PRECISION 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.

SunSoft, Inc.  —  Last change: 27 Jun 1995