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/*
ARPACK++ v1.0 8/1/1997
c++ interface to ARPACK code.
MODULE BSymReg.cc.
Example program that illustrates how to solve a real
symmetric banded standard eigenvalue problem in regular
mode using the ARluSymStdEig class.
1) Problem description:
In this example we try to solve A*x = x*lambda in regular
mode, where A is derived from the standard central difference
discretization of the 2-dimensional Laplacian on the unit
square with zero Dirichlet boundary conditions.
2) Data structure used to represent matrix A:
{nsdiag, A}: matrix A data in symmetric band format. The elements
of the main diagonal and the first nsdiag subdiagonals of A are
stored sequentially, by columns, in vector A.
3) Included header files:
File Contents
----------- -------------------------------------------
bsmatrxa.h BandMatrixA, a function that generates
matrix A in band format.
arbsmat.h The ARbdSymMatrix class definition.
arbssym.h The ARluSymStdEig class definition.
lsymsol.h The Solution function.
4) ARPACK Authors:
Richard Lehoucq
Kristyn Maschhoff
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#include "bsmatrxa.h"
#include "arbsmat.h"
#include "arbssym.h"
#include "lsymsol.h"
main()
{
// Defining variables;
int nx;
int n; // Dimension of the problem.
int nsdiag; // Lower (and upper) bandwidth of A.
double* A; // Pointer to an array that stores the elements of A.
// Creating a 100x100 matrix.
nx = 10;
BandMatrixA(nx, n, nsdiag, A);
ARbdSymMatrix<double> matrix(n, nsdiag, A);
// Defining what we need: the four eigenvectors of A with largest magnitude.
ARluSymStdEig<double> dprob(4, matrix);
// Finding eigenvalues and eigenvectors.
dprob.FindEigenvectors();
// Printing solution.
Solution(matrix, dprob);
} // main.
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