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/*
ARPACK++ v1.0 8/1/1997
c++ interface to ARPACK code.
MODULE LCMatrxE.h
Function template for the stiffness matrix formed by using
piecewise linear elements on [0,1].
ARPACK Authors
Richard Lehoucq
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#ifndef LCMATRXE_H
#define LCMATRXE_H
#include "arcomp.h"
template<class FLOAT, class INT>
void CompMatrixE(INT n, arcomplex<FLOAT> rho, INT& nnz,
arcomplex<FLOAT>* &A, INT* &irow, INT* &pcol)
{
INT i, j;
arcomplex<FLOAT> dd, dl, du, s, h;
// Defining constants.
const arcomplex<FLOAT> one( 1.0, 0.0);
const arcomplex<FLOAT> two( 2.0, 0.0);
h = one/arcomplex<FLOAT>((FLOAT)(n+1),0.0);
s = rho/two;
dd = two/h;
dl = -(one/h) - s;
du = -(one/h) + s;
// Defining the number of nonzero matrix elements.
nnz = 3*n-2;
// Creating output vectors.
A = new arcomplex<FLOAT>[nnz];
irow = new INT[nnz];
pcol = new INT[n+1];
// Filling A, irow and pcol.
pcol[0] = 0;
j = 0;
for (i=0; i!=n; i++) {
if (i) {
irow[j] = i-1;
A[j++] = du;
}
irow[j] = i;
A[j++] = dd;
if (i!=(n-1)) {
irow[j] = i+1;
A[j++] = dl;
}
pcol[i+1] = j;
}
} // CompMatrixE.
#endif // LCMATRXE_H
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