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/*
ARPACK++ v1.0 8/1/1997
c++ interface to ARPACK code.
MODULE LNMatrxW.h
Class template for the m by n matrix A with entries
A(i,j) = k*(s(i))*(t(j)-1), if j-nl<= i <= j;
k*(t(j))*(s(i)-1), if j < i <= j+nu,
where s(i) = i/(m+1), t(j) = j/(n+1) and k = 1/(n+1).
ARPACK Authors
Richard Lehoucq
Danny Sorensen
Chao Yang
Dept. of Computational & Applied Mathematics
Rice University
Houston, Texas
*/
#ifndef LNMATRXW_H
#define LNMATRXW_H
template<class FLOAT, class INT>
void MatrixW(int m, int n, int nl, int nu, int& nnz,
FLOAT* &A, INT* &irow, INT* &pcol)
{
int i, j, l, u, mn, p;
FLOAT h, k;
// Defining constants.
l = nl-m+n;
l = (l<0)?0:((l>nl)?nl:l);
u = nu-n+m;
u = (u<0)?0:((u>nu)?nu:u);
h = 1.0/FLOAT(m+1);
k = 1.0/FLOAT(n+1);
// Defining the number of nonzero elements and lines of the matrix.
mn = (m<n)?m:n;
nnz = mn*(nl+nu+1)-(l*l+l)/2-(u*u+u)/2;
// Creating output vectors.
A = new FLOAT[nnz];
irow = new INT[nnz];
pcol = new INT[n+1];
// Filling A, irow and pcol.
pcol[0] = 0;
p = 0;
for (j=0; j!=n; j++) {
for(i=((j-nu)>0)?(j-nu):0; ((i<=j)&&(i<m)); i++) {
irow[p] = i;
A[p++] = k*(FLOAT(i+1)*h-1.0)*(FLOAT(j+1)*k);
}
for(i=j+1; ((i<=(j+nl))&&(i<m)); i++) {
irow[p] = i;
A[p++] = k*(FLOAT(j+1)*k-1.0)*(FLOAT(i+1)*h);
}
pcol[j+1] = p;
}
} // MatrixW.
#endif // LNMATRXW_H
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