ssterf3lapack
Computes all eigenvalues of a symmetric tridiagonal matrix using the pal-walker-kahan variant of the ql or qr algorithm
Usage
- 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.