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/*
ARPACK++ v1.2 2/20/2000
c++ interface to ARPACK code.
MODULE BNMatrxD.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 BNMATRXD_H
#define BNMATRXD_H
template<class ARFLOAT, class ARINT>
void BandMatrixD(ARINT nx, ARFLOAT rho, ARINT& n, ARINT& nL, ARINT& nU,
ARFLOAT* &A)
{
ARINT i, j, lda;
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 number of columns and the upper and lower bandwidth.
n = nx*nx;
nL = nx;
nU = nx;
// Creating output vector A.
lda = nL+nU+1;
A = new ARFLOAT[n*lda];
// Filling A with zeros.
for (j=0; j<(n*lda); j++ ) A[j] = (ARFLOAT)0.0;
// Creating matrix A.
for (i=0, j=nU; i<n; i++, j+=lda) {
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;
}
} // BandMatrixD.
#endif // BNMATRXD_H
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