ZLAED0
November 2006
Purpose
Using the divide and conquer method, ZLAED0 computes all eigenvalues
of a symmetric tridiagonal matrix which is one diagonal block of
those from reducing a dense or band Hermitian matrix and
corresponding eigenvectors of the dense or band matrix.
of a symmetric tridiagonal matrix which is one diagonal block of
those from reducing a dense or band Hermitian matrix and
corresponding eigenvectors of the dense or band matrix.
Arguments
| QSIZ |
(input) INTEGER
The dimension of the unitary matrix used to reduce
the full matrix to tridiagonal form. QSIZ >= N if ICOMPQ = 1. |
| N |
(input) INTEGER
The dimension of the symmetric tridiagonal matrix. N >= 0.
|
| D |
(input/output) DOUBLE PRECISION array, dimension (N)
On entry, the diagonal elements of the tridiagonal matrix.
On exit, the eigenvalues in ascending order. |
| E |
(input/output) DOUBLE PRECISION array, dimension (N-1)
On entry, the off-diagonal elements of the tridiagonal matrix.
On exit, E has been destroyed. |
| Q |
(input/output) COMPLEX*16 array, dimension (LDQ,N)
On entry, Q must contain an QSIZ x N matrix whose columns
unitarily orthonormal. It is a part of the unitary matrix that reduces the full dense Hermitian matrix to a (reducible) symmetric tridiagonal matrix. |
| LDQ |
(input) INTEGER
The leading dimension of the array Q. LDQ >= max(1,N).
|
| IWORK |
(workspace) INTEGER array,
the dimension of IWORK must be at least
6 + 6*N + 5*N*lg N ( lg( N ) = smallest integer k such that 2^k >= N ) |
| RWORK |
(workspace) DOUBLE PRECISION array,
dimension (1 + 3*N + 2*N*lg N + 3*N**2)
( lg( N ) = smallest integer k such that 2^k >= N ) |
| QSTORE |
(workspace) COMPLEX*16 array, dimension (LDQS, N)
Used to store parts of
the eigenvector matrix when the updating matrix multiplies take place. |
| LDQS |
(input) INTEGER
The leading dimension of the array QSTORE.
LDQS >= max(1,N). |
| INFO |
(output) INTEGER
= 0: successful exit.
< 0: if INFO = -i, the i-th argument had an illegal value. > 0: The algorithm failed to compute an eigenvalue while working on the submatrix lying in rows and columns INFO/(N+1) through mod(INFO,N+1). |