Regular Inverse Mode

  Driver dndrv3  uses the regular inverse mode to solve the generalized eigenvalue problem. This mode should be used if ${\bf M}$ is symmetric and positive definite but it is not possible to factor into a Cholesky factorization or if there is reason to think that ${\bf M}$ is ill-conditioned. To use dndrv3 the user must supply the action of

The action of is typically done with an iterative solver such as pre-conditioned conjugate gradient. If ${\bf M}$ can be factored then direct conversion to a standard problem is recommended. This driver is appropriate for which = 'LM','LR', 'SR','LI','SI'         settings. If interior eigenvalues are sought then driver dndrv4 is probably more appropriate. If convergence is slower than desired then one of the shift-invert modes described below should be used.