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/*
ARPACK++ v1.2 2/20/2000
c++ interface to ARPACK code.
MODULE DNMatrxD.h
Function template for the block tridiagonal matrix A, whose
diagonal blocks are tridiagonal with 4 on the diagonal,
-1-rho*h/2 on the subdiagonal and -1+rho*h/2 on the superdiagonal.
Each off-diagonal block of A is an identity matrix.
ARPACK Authors
Richard Lehoucq
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#ifndef DNMATRXD_H
#define DNMATRXD_H
template<class ARFLOAT, class ARINT>
void DenseMatrixD(ARINT nx, ARFLOAT rho, ARINT& n, ARFLOAT* &A)
{
ARINT i, j;
ARFLOAT dd, dl, du, h;
// Defining constants.
h = 1.0/ARFLOAT(nx+1);
dd = 4.0;
dl = -1.0 - 0.5*rho*h;
du = -1.0 + 0.5*rho*h;
// Defining the dimension of A.
n = nx*nx;
// Creating output vector A.
A = new ARFLOAT[n*n];
for (i=0; i<n*n; i++) A[i]=0.0;
for (i=0, j=0; i<n; i++, j+=n+1) {
if (i>=nx) A[j-nx] = -1.0;
if (i%nx) A[j-1] = du;
A[j] = dd;
if ((i+1)%nx) A[j+1] = dl;
if (i<(n-nx)) A[j+nx] = -1.0;
}
} // DenseMatrixD.
#endif // DNMATRXD_H
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