This chapter is structured as follows. The naming conventions used in ARPACK, and the data types and precisions available are described in § 3.1. Spectral transformations are discussed in § 3.2. Spectral transformations are usually extremely effective but there are a number of problem dependent issues that determine which one to use. In § 3.3 we describe the reverse communication interface needed to exercise the various shift-invert options. Each shift-invert option is specified as a computational mode and all of these are summarized in the remaining sections. There is a subsection for each problem type and hence these sections are quite similar and repetitive. Once the basic idea is understood, it is probably best to turn directly to the subsection that describes the problem setting that is most interesting to you.
Perhaps the easiest way to rapidly become acquainted with the modes of ARPACK is to run the example driver routines (see Appendix A) that have been supplied for each of the modes. These may be used as templates and adapted to solve specific problems.