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/*
ARPACK++ v1.2 2/20/2000
c++ interface to ARPACK code.
MODULE LNMatrxD.h
Function template for the mass 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 LNMATRXD_H
#define LNMATRXD_H
template<class ARFLOAT, class ARINT>
void MassMatrix(ARINT n, ARINT& nnz, ARFLOAT* &A, ARINT* &irow, ARINT* &pcol)
{
ARINT i,j;
ARFLOAT diag, sub;
// Defining constants.
sub = 1.0/6.0/ARFLOAT(n+1);
diag = 4.0/6.0/ARFLOAT(n+1);
// Defining the number of nonzero matrix elements.
nnz = 3*n-2;
// Creating output vectors.
A = new ARFLOAT[nnz];
irow = new ARINT[nnz];
pcol = new ARINT[n+1];
// Filling A, irow and pcol.
pcol[0] = 0;
j = 0;
for (i=0; i!=n; i++) {
if (i != 0) {
irow[j] = i-1;
A[j++] = sub;
}
irow[j] = i;
A[j++] = diag;
if (i != (n-1)) {
irow[j] = i+1;
A[j++] = sub;
}
pcol[i+1] = j;
}
} // MassMatrix.
#endif // LNMATRXD_H
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