Standard Mode

Driver dsdrv1  solves the standard eigenvalue problem

This mode only requires matrix vector products with It is most appropriate for computing extremal, non-clustered eigenvalues. This mode can be successful for clustered eigenvalues, but convergence is often much slower in this case. Since this mode is generally the easiest to try, it is recommended to use it initially and convert to more appropriate modes after some information about the distribution of the spectrum has been obtained. It can be particularly useful to run initially with which = 'BE' with a loose tolerance just to get an idea of the largest and smallest eigenvalues.