1. Purpose ------- This directory contains example drivers that call ARPACK subroutines [s,d]naupd.f and [s,d]neupd.f to solve real NONSYMMETRIC eigenvalue problems using regular, inverse or shift-invert modes. These drivers illustrate how to set various ARPACK parameters to solve different problems in different modes. They provide a guideline on how to use ARPACK's reverse communication interface. The user may modify any one of these drivers, and provide his/her own matrix vector multiplication routine to solve the problem of his/her own interest. 2. Naming convention ----------------- The name for each driver has the form 'XndrvN.f', where X - is 's' (single precision) or 'd' (double precision) N - is a number between 1 and 6. If N = 1, the driver solves a STANDARD eigenvalue problem in REGULAR mode. N = 2, the driver solves a STANDARD eigenvalue problem in SHIFT-INVERT mode with a REAL shift. N = 3, the driver solves a GENERALIZED eigenvalue problem in INVERSE mode. N = 4, the driver solves a GENERALIZED eigenvalue problem in SHIFT-INVERT mode with a REAL shift. These are 4 commonly used drivers. For shift-invert (N=2,4) mode the user needs to supply a linear system solver to perform y=inv[A-sigma*B]*x. If N > 4, shift-invert is used with a complex shift whose imaginary part is nonzero. If N = 5, the driver solves a GENERALIZED eigenvalue problem using mode 3 of [s,d]naupd. N = 6. the driver solves a GENERALIZED eigenvalue problem using mode 4 of [s,d]naupd. These two drivers require the user to provide COMPLEX arithmetic linear system solver. For more information on the use of complex shift, see the following reference: B.N. Parlett & Y. Saad, "Complex Shift and Invert Strategies for Real Matrices", Linear Algebra and its Applications, vol 88/89, pp 575-595, (1987). 3. Usage ----- To run these drivers, you may use the makefile in this directory and issue, for example, "make sndrv1". Then execute using "sndrv1".