1. Purpose 
   -------
   This directory contains example drivers that call ARPACK subroutines
   __aupd.f and __eupd.f to solve various eigenvalue problems using regular, 
   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 supply his/her own matrix vector
   multiplication routine to solve the problem of his/her own interest.
   These drivers are installed in the following subdirectories.

   SIMPLE  ---   simple drivers for beginners.
   SYM     ---   drivers for symmetric eigenvalue problems
   NONSYM  ---   drivers for nonsymmetric eigenvalue problems
   COMPLEX ---   drivers for eigenvalue problem with complex matrices
   BAND    ---   drivers for eigenvalue problem with BANDED matrices 
   SVD     ---   drivers for computing singular values and vectors
                 of a m by n matrix.


2. Getting started
   ---------------
   If you have never used ARPACK before, it might be a good idea
   to go into the subdirectory SIMPLE, and read one of the
   simple drivers [s,d]ssimp.f, [s,d]nsimp.f [c,z]nsimp.f
   first.  The documentation explains how to use ARPACK in 
   considerable detail.  To run these drivers, you may use the 
   makefile in that directory and issue, for example, 
   "make sssimp", and then execute using "sssimp"

   The output should look like: 

   _saupd: number of update iterations taken
   -----------------------------------------
      1 -    1:     5


   _saupd: number of "converged" Ritz values
   -----------------------------------------
      1 -    1:     4
  
  
   _saupd: final Ritz values
   -------------------------
      1 -    4:   8.912E+02   9.198E+02   9.198E+02   9.484E+02


   _saupd: corresponding error bounds
   ----------------------------------
      1 -    4:   4.686E-11   1.905E-08   1.050E-10   5.700E-19



     ==========================================
     = Symmetric implicit Arnoldi update code =
     = Version Number: 2.1                    =
     = Version Date:   11/15/95               =
     ==========================================
     = Summary of timing statistics           =
     ==========================================


     Total number update iterations             =     5
     Total number of OP*x operations            =    78
     Total number of B*x operations             =     0
     Total number of reorthogonalization steps  =    78
     Total number of iterative refinement steps =     0
     Total number of restart steps              =     0
     Total time in user OP*x operation          =     0.066667
     Total time in user B*x operation           =     0.000000
     Total time in Arnoldi update routine       =     1.166667
     Total time in ssaup2 routine               =     1.166667
     Total time in basic Arnoldi iteration loop =     0.216667
     Total time in reorthogonalization phase    =     0.066667
     Total time in (re)start vector generation  =     0.000000
     Total time in trid eigenvalue subproblem   =     0.050000
     Total time in getting the shifts           =     0.000000
     Total time in applying the shifts          =     0.900000
     Total time in convergence testing          =     0.000000

   Ritz values and relative residuals
   ----------------------------------
               Col   1       Col   2
    Row   1:    8.91167E+02   6.95597E-07
    Row   2:    9.19781E+02   3.30156E-07
    Row   3:    9.19781E+02   4.25717E-07
    Row   4:    9.48395E+02   3.20519E-07


    _SSIMP
    ======

    Size of the matrix is   100
    The number of Ritz values requested is   4
    The number of Arnoldi vectors generated (NCV) is   20
    What portion of the spectrum: LM
    The number of converged Ritz values is   4
    The number of Implicit Arnoldi update iterations taken is   5
    The number of OP*x is   78
    The convergence criterion is     5.96046E-08

  
3. Convention 
   ----------
   The naming convention for each driver is explained in
   the README file in each subdirectory. 

4. LAPACK & BLAS routines
   ----------------------
   All ARPACK codes assume the use of LAPACK version 2.0 codes.
   LAPACK and BLAS routines needed for each driver program are
   listed at the beginning of the documentation in each driver 
   program.

