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SPARSKIT MODULE MATGEN

The current directory MATGEN contains a few subroutines and
drivers for generating sparse matrices.
1) 5pt and 7pt matrices on rectangular regions discretizing
elliptic operators of the form:
L u == delx( a delx u ) + dely ( b dely u) + delz ( c delz u ) +
delx ( d u ) + dely (e u) + delz( f u ) + g u = h u
with Boundary conditions,
alpha del u / del n + beta u = gamma
on a rectangular 1D, 2D or 3D grid using centered
difference scheme or upwind scheme.
The functions a, b, ..., h are known through the
subroutines afun, bfun, ..., hfun in the file
functns.f. The alpha is a constant on each side of the
rectanglar domain. the beta and the gamma are defined
by the functions betfun and gamfun (see functns.f for
examples).
2) block version of the finite difference matrices (several degrees of
freedom per grid point. ) It only generates the matrix (without
the righthandside), only Dirichlet Boundary conditions are used.
3) Finite element matrices for the convectiondiffusion problem
 Div ( K(x,y) Grad u ) + C(x,y) Grad u = f
u = 0 on boundary
(with Dirichlet boundary conditions). The matrix is returned
assembled in compressed sparse row format. See genfeu for
matrices in unassembled form. The user must provide the grid,
(coordinates x, y and connectivity matrix ijk) as well as some
information on the nodes (nodcode) and the material properties
(the function K(x,y) above) in the form of a subroutine xyk.
4) Markov chain matrices arising from a random walk on a
trangular grid. Useful for testing nonsymmetric eigenvalue
codes. Has been suggested by G.W. Stewart in one of his
papers. Used by Y. Saad in several papers as a test problem
for nonsymmetric eigenvalue methods.
5) Matrices from the paper by Z. Zlatev, K. Schaumburg,
and J. Wasniewski. (``A testing scheme for subroutines solving
large linear problems.'' Computers and Chemistry, 5:91100,
1981.)

the items (1) and (2) are in directory FDIF,
the item (3) is in directory FEM
the items (4) and (5) are in directory MISC
