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Arguments

A
(input/output) REAL or COMPLEX square array, shape $(:,:)$.
On entry, the matrix $A$.
If ${\bf UPLO} =$ 'U', the upper triangular part of ${\bf A}$ contains the upper triangular part of matrix $A$. If ${\bf UPLO} =$ 'L', the lower triangular part of ${\bf A}$ contains the lower triangular part of matrix $A$.
On exit, if ${\bf JOBZ} =$ 'V', then the columns of ${\bf A}$ contain the eigenvectors, normalized as follows:

\begin{optionarg}
\item[{if ${\bf ITYPE} = 1$\ or $2$:}] $Z^H\,B\,Z = I$,
\item[{if ${\bf ITYPE} = 3$:}] $Z^H\,B^{-1}\,Z = I$.
\end{optionarg}
If JOBZ = 'N', then the upper triangle (if UPLO = 'U') or the lower triangle (if UPLO = 'L') of $A$, including the diagonal, is destroyed.

B
(input/output) REAL or COMPLEX square array, shape $(:,:)$ with $size({\bf B},1) = size({\bf A},1)$.
On entry, the matrix $B$. If ${\bf UPLO} =$ 'U', the upper triangular part of ${\bf B}$ contains the upper triangular part of matrix $B$. If ${\bf UPLO} =$ 'L', the lower triangular part of ${\bf B}$ contains the lower triangular part of matrix $B$.
On exit, if the part of ${\bf B}$ containing the matrix is overwritten by the triangular factor $U$ or $L$ of the Cholesky factorization $B = U^H\,U$ or $B = L\,L^H$, respectively.

W
(output) REAL array, shape $(:)$ with $size({\bf W}) = size({\bf A},1)$.
The eigenvalues in ascending order.

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

\begin{optionarg}
\item[{= 1:}] $A z = \lambda B z$ \item[{= 2:}] $A B z = \lambda z$ \item[{= 3:}] $B A z = \lambda z$ \end{optionarg}
Default value: 1.

JOBZ
Optional (input) CHARACTER(LEN=1).

\begin{optionarg}
\item[{= 'N':}] Compute eigenvalues only;
\item[{= 'V':}] Compute eigenvalues and eigenvectors.
\end{optionarg}
Default value: 'N'.

UPLO
Optional (input) CHARACTER(LEN=1).

\begin{optionarg}
\item[{$ =$\ 'U':}] Upper triangles of $A$\ and $B$\ are stor...
...item[{$ =$\ 'L':}] Lower triangles of $A$\ and $B$\ are stored.
\end{optionarg}
Default value: 'U'.

INFO
Optional (output) INTEGER.

\begin{infoarg}
\item[{$= 0$:}] successful exit.
\item[{$< 0$:}] if {\bf INFO}...
...genvectors were computed.
\end{infoarg} $n$\ is the order of $A$.
\end{infoarg}
If INFO is not present and an error occurs, then the program is terminated with an error message.
References: [1] and [17,9,20].
next up previous contents index
Next: Examples Up: Generalized Symmetric Eigenvalue Problems Previous: Purpose   Contents   Index
Susan Blackford 2001-08-19