Arguments

AP

(input/output) REAL or COMPLEX array, shape $(:)$ with $size({\bf AP}) = n(n+1)/2$, where $n$ is the order of $A$ and $B$.
On entry, the upper or lower triangle of matrix $A$ in packed storage. The elements are stored columnwise as follows:

$$\begin{array}{c\vert c\vert c} A_{i,j} & i,j & {\bf UPLO} ... ... \leq i \leq n \end{array} & \mbox{ 'L'} \\ \hline \end{array}$$

On exit, the contents of AP are destroyed.

BP

(input/output) REAL or COMPLEX array, shape $(:)$ and $size({\bf BP}) = size({\bf AP})$.
On entry, the upper or lower triangle of matrix $B$ in packed storage. The elements are stored columnwise as follows:

$$\begin{array}{c\vert c\vert c} B_{i,j} & i,j & {\bf UPLO} ... ...j \leq i \leq n \end{array} & \mbox{'L'} \\ \hline \end{array}$$

On exit, the triangular factor $U$ or $L$ of the Cholesky factorization $B = U^H\,U$ or $B = L\,L^H$, in the same storage format as $B$.

W

(output) REAL array, shape $(:)$ with $size$(W) $= n$.
The eigenvalues in ascending order.

ITYPE

Optional (input) INTEGER.
Specifies the problem type to be solved:


Default value: 1.

UPLO

Optional (input) CHARACTER(LEN=1).


Default value: 'U'.

Z

Optional (output) REAL or COMPLEX square array, shape $(:,:)$ with $size$(Z,1) $= n$.
The matrix $Z$ of eigenvectors, normalized as follows:

INFO

Optional (output) INTEGER.


If INFO is not present and an error occurs, then the program is terminated with an error message.

References: [1] and [17,9,20].