Arguments

D

(input/output) REAL array shape $(:)$ with $size$(D) $= n$, where $n$ is the order of $A$.
On entry, the diagonal elements of the matrix $A$.
On exit, the eigenvalues in ascending order.

E

(input/output) REAL array, shape $(:)$ with $size$(E) $= n$.
On entry, the $n - 1$ subdiagonal elements of $A$ in E$_1$ to E$_{n-1}\,$. ${\bf E}_n$ need not be set but is used by the routine.
On exit, the contents of E are destroyed.

Z

Optional (output) REAL square array, shape$(:,:)$ with $size$(Z,1) $= n$.
The columns of ${\bf Z}$ contain the orthonormal eigenvectors of $A$ in the order of the eigenvalues.

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].