F12FFF is a setup routine for
F12FGF which can be used to find some eigenvalues (and optionally the corresponding eigenvectors) of a standard or generalized eigenvalue problem defined by real, banded, symmetric matrices. The banded matrix must be stored using the LAPACK storage format for real banded nonsymmetric matrices.
The pair of routines F12FFF and
F12FGF together with the option setting routine
F12FDF 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 symmetric.
F12FFF is a setup routine which must be called before the option setting routine
F12FDF and the solver routine
F12FGF. Internally,
F12FGF makes calls to
F12FBF and
F12FCF; the routine documents for
F12FBF and
F12FCF 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
F12FDF, 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 F12FDF.
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 F12FFF is illustrated by the example program of
F12FGF (see
Section 9 in F12FGF).