The eigenvalues and eigenvectors of
and can be extracted with a call to `dneupd` when using
drivers `dndrv1 - dndrv4`. However, since
the eigenvalues computed for `OP` by the drivers `dndrv5` and
`dndrv6` are related to the eigenvalues of by

respectively. These equations do not have a unique solution and it appears to be difficult to match the correct solution with
a given eigenvector.
Thus, the Rayleigh Quotient must be formed by the user to obtain the
eigenvalue corresponding to the eigenvector This will be done
automatically in `dneupd` in a later release of ARPACK.

Once the converged eigenvalues and eigenvectors have been obtained the user may check the accuracy of the results by computing the direct residuals and for a standard or generalized eigenvalue problems. Residual checking is provided in all drivers.