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/*
ARPACK++ v1.2 2/18/2000
c++ interface to ARPACK code.
MODULE DCompShf.cc.
Example program that illustrates how to solve a complex standard
eigenvalue problem in shift and invert mode using the
ARluCompStdEig class.
1) Problem description:
In this example we try to solve A*x = x*lambda in shift and invert
mode, where A is derived from the central difference discretization
of the convection-diffusion operator
(Laplacian u) + rho*(du / dx)
on the unit square [0,1]x[0,1] with zero Dirichlet boundary
conditions.
2) Data structure used to represent matrix A:
{ndiagL, ndiagU, A}: matrix A data in band format. The columns
of A are stored sequentially in vector A. ndiagL and ndiagU
supply the lower and upper bandwidth of A, respectively.
3) Library called by this example:
The LAPACK package is called by ARluCompStdEig to solve
some linear systems involving (A-sigma*I). This is needed to
implement the shift and invert strategy.
4) Included header files:
File Contents
----------- ---------------------------------------------
bcmatrxa.h CompMatrixB, a function that generates matrix
A in band format.
arbnsmat.h The ARbdNonSymMatrix class definition.
arbscomp.h The ARluCompStdEig class definition.
lcompsol.h The Solution function.
arcomp.h The "arcomplex" (complex) type definition.
5) ARPACK Authors:
Richard Lehoucq
Kristyn Maschhoff
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#include "arcomp.h"
#include "arbnsmat.h"
#include "arbscomp.h"
#include "bcmatrxa.h"
#include "lcompsol.h"
int main()
{
// Defining variables;
int nx;
int n; // Dimension of the problem.
int ndiagL; // Lower bandwidth of A and B.
int ndiagU; // Upper bandwidth of A and B.
arcomplex<double>* valA; // pointer to an array that stores
// the elements of A.
// Creating a complex matrix.
nx = 10;
CompMatrixA(nx, n, ndiagL, ndiagU, valA);
ARbdNonSymMatrix<arcomplex<double>, double> A(n, ndiagL, ndiagU, valA);
// Defining what we need: the four eigenvectors of F nearest to 0.0.
ARluCompStdEig<double> dprob(4L, A, arcomplex<double>(0.0, 0.0));
// Finding eigenvalues and eigenvectors.
dprob.FindEigenvectors();
// Printing solution.
Solution(A, dprob);
} // main.
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