NAME
DSTERF - computes 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.