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/*
ARPACK++ v1.2 2/20/2000
c++ interface to ARPACK code.
MODULE DCMatrxB.h
Function template for the tridiagonal matrix derived from
the standard central difference of the 1-d convection diffusion
operator u" + rho*u' on the interval [0, 1] with zero
Dirichlet boundary conditions.
ARPACK Authors
Richard Lehoucq
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#ifndef DCMATRXB_H
#define DCMATRXB_H
#include "arcomp.h"
template<class ARFLOAT, class ARINT>
void CompMatrixB(ARINT n, arcomplex<ARFLOAT> rho, arcomplex<ARFLOAT>* &A)
{
ARINT i, j;
arcomplex<ARFLOAT> dd, dl, du, h;
// Defining constants.
const arcomplex<ARFLOAT> one( 1.0, 0.0);
const arcomplex<ARFLOAT> two( 2.0, 0.0);
const arcomplex<ARFLOAT> half( 0.5, 0.0);
h = one/arcomplex<ARFLOAT>((ARFLOAT)(n+1),0.0);
dd = two/h;
dl = -(one/h) - half*rho;
du = -(one/h) + half*rho;
// Creating output vector A.
A = new arcomplex<ARFLOAT>[n*n];
for (i=0; i<n*n; i++) A[i] = arcomplex<ARFLOAT>(0.0, 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;
}
} // CompMatrixB.
#endif // DCMATRXB_H
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