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来自「这是Yousef Saad编写的矩阵运算的Fortran软件包（A basic 」· 代码 · 共 32 行

This directory contains the routines that generate finite difference
matrices from a second order elliptic operator.

      1) 5-pt and 7-pt 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 1-D, 2-D or 3-D 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 right-hand-side), only Dirichlet Boundary conditions are used.

genmat.f ---- the matrix generation routines.
functns.f --- functions used by the genmat.f

to test the 5-point/7-point matrix please see mak57pt
to test the block version of the 5-point/7-point matrix see mak57bl