At first we can get the Lagrangian function from the ellipticequation, then replace differential coefficient by difference and get the discrete Lagrangian function.
给定一个椭圆方程，我们先找出这个方程的拉氏函数，用差分代替微分，得到离散的拉氏函数。
2
This paper studies the necessary and sufficient condition of uniformly convergent difference scheme for the elliptic-parabolic partial differential equation with a small parameter.