df=(f(i+1,j}+beta2*f(i,j+1}+f(i-1,j}+beta2*f(i,j-1} -d*f(i,j}-fxy*dx**2}/d

The data set used to illustrate subroutine pde3 is taken from Example 9.6. The output generated by the program is presented in Output 9.3.

Output 9.3. Solution of the Poisson equation with Dirichlet Bes by the five-point method

The Poisson equation solver can be extended to account for Neumann (i.e., derivative) BCs in the manner described in Section 9.13.2 for the Laplace equation solver.

9.13.4 Packages for Integrating the Laplace and Poisson Equations Numerous libraries and software packages are available for integrating the Laplace and Poisson equations. Many work stations and main frame computers have such libraries attached to their operating systems.