1. Purpose ------- This directory contains example drivers that call ARPACK subroutines [s,d]saupd.f and [s,d]seupd.f to solve SYMMETRIC eigenvalue problems using regular, inverse, shift-invert or other special modes (such as Cayley, Bucking etc.) 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 'XsdrvN.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. 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. 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. When N > 4, a special mode is used. If N = 5, the driver solves a GENERALIZED eigenvalue problem in BUCKLING mode. N = 6, the driver solves a GENERALIZED eigenvalue problem in CAYLEY mode. These two drivers require the user to provide linear system solvers also. For more information on Cayley and Buckling mode, see the following reference: R.G. Grimes, J.G. Lewis and H.D. Simon, "A Shifted Block Lanczos Algorithm for Solving Sparse Symmetric Generalized Eigenproblems", SIAM J. Matr. Anal. Apps., January (1993). 3. Usage ----- To run these drivers, you may use the makefile in this directory and issue, for example, "make ssdrv1". Then execute using "ssdrv1".