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.
