- AP
- (
*input/output*)**REAL**or**COMPLEX**array, shape with , where is the order of .

On entry, the upper or lower triangle of matrix in packed storage. The elements are stored columnwise as follows:

On exit, is overwritten by values generated during the reduction of to a tridiagonal matrix . If 'U', the diagonal and first superdiagonal of T overwrite the corresponding diagonals of . If 'L', the diagonal and first subdiagonal of T overwrite the corresponding diagonals of .

- W
- (
*output*)**REAL**array, shape with .

The eigenvalues in ascending order. - UPLO
*Optional*(*input*)**CHARACTER(LEN=1)**.

Default value: 'U'.- Z
*Optional*(*output*)**REAL**or**COMPLEX**square array, shape with .

The columns of contain the orthonormal eigenvectors of 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.