SSTEV
November 2006
Purpose
SSTEV computes all eigenvalues and, optionally, eigenvectors of a
real symmetric tridiagonal matrix A.
real symmetric tridiagonal matrix A.
Arguments
| JOBZ |
(input) CHARACTER*1
= 'N': Compute eigenvalues only;
= 'V': Compute eigenvalues and eigenvectors. |
| 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
A. 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 A, stored in elements 1 to N-1 of E. On exit, the contents of E are destroyed. |
| Z |
(output) REAL array, dimension (LDZ, N)
If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal
eigenvectors of the matrix A, with the i-th column of Z holding the eigenvector associated with D(i). If JOBZ = 'N', then Z is not referenced. |
| LDZ |
(input) INTEGER
The leading dimension of the array Z. LDZ >= 1, and if
JOBZ = 'V', LDZ >= max(1,N). |
| WORK |
(workspace) REAL array, dimension (max(1,2*N-2))
If JOBZ = 'N', WORK is not referenced.
|
| INFO |
(output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of E did not converge to zero. |