F12AFF is a setup routine for
F12AGF which may be used for finding some eigenvalues (and optionally the corresponding eigenvectors) of a standard or generalized eigenvalue problem defined by real, banded, nonsymmetric matrices. The banded matrix must be stored using the LAPACK column ordered storage format for real banded nonsymmetric matrices (see
Section 3.3.4 in the F07 Chapter Introduction).
The pair of routines F12AFF and
F12AGF together with the option setting routine
F12ADF are designed to calculate some of the eigenvalues,
$\lambda $, (and optionally the corresponding eigenvectors,
$x$) of a standard eigenvalue problem
$Ax=\lambda x$, or of a generalized eigenvalue problem
$Ax=\lambda Bx$ of order
$n$, where
$n$ is large and the coefficient matrices
$A$ and
$B$ are banded real and nonsymmetric.
F12AFF is a setup routine which must be called before the option setting routine
F12ADF and the solver routine
F12AGF. Internally,
F12AGF makes calls to
F12ABF and
F12ACF; the routine documents for
F12ABF and
F12ACF should be consulted for details of the algorithm used.
This setup routine initializes the communication arrays, sets (to their default values) all options that can be set by you via the option setting routine
F12ADF, and checks that the lengths of the communication arrays as passed by you are of sufficient length. For details of the options available and how to set them, see
Section 10.1 in F12ADF.
Lehoucq R B and Scott J A (1996) An evaluation of software for computing eigenvalues of sparse nonsymmetric matrices Preprint MCS-P547-1195 Argonne National Laboratory
Lehoucq R B and Sorensen D C (1996) Deflation techniques for an implicitly restarted Arnoldi iteration SIAM Journal on Matrix Analysis and Applications 17 789–821
If on entry
${\mathbf{IFAIL}}={\mathbf{0}}$ or
${-{\mathbf{1}}}$, explanatory error messages are output on the current error message unit (as defined by
X04AAF).
Not applicable.
None.
The use of F12AFF is illustrated in
Section 9 in F12AGF.