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/*
ARPACK++ v1.0 8/1/1997
c++ interface to ARPACK code.
MODULE DNMatrxB.h
Function template for the stiffness matrix obtained from
the finite element discretization of the 1-dimensional
convection diffusion operator d^2u/dx^2 + rho*(du/dx) on
the interval [0,1] with zero Dirichlet boundary conditions
using linear elements.
ARPACK Authors
Richard Lehoucq
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#ifndef DNMATRXB_H
#define DNMATRXB_H
template<class FLOAT, class INT>
void StiffnessMatrix(INT n, FLOAT rho, FLOAT* &A)
{
INT i, j;
FLOAT dd, dl, du, h;
// Defining constants.
h = 1.0/FLOAT(n+1);
dd = 2.0/h;
dl = -1.0/h - 0.5*rho;
du = -1.0/h + 0.5*rho;
// Creating output vector A.
A = new FLOAT[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) A[j-1] = du;
A[j] = dd;
if (n-i-1) A[j+1] = dl;
}
} // StiffnessMatrix.
#endif // DNMATRXB_H
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