Discrete Poisson equation: Difference between revisions

respectively.
 
From the above, it can be inferred that there are <math>n</math> block columns of <math> m </math> in <math> A </math>. It is important to note that prescribed values of <math> u </math> (usually lying on the boundary) would have their corresponding elements removed from <math> I </math> and <math> D </math>. For the common case that all the nodes on the boundary are set, we have <math> 2 \le i \le m - 1 </math> and <math> 2 \le j \le n - 1 </math>, and the system would have the dimensions (''m''&nbsp;&minus;&nbsp;2)(''n''&nbsp;&miunsminus;&nbsp;2)&nbsp;&times;&nbsp;(''m''&nbsp;&miunsminus;&nbsp;2)(''n''&nbsp;&miunsminus;&nbsp;2), where <math> D </math> and <math> I </math> would have dimensions&nbsp;(''m''&nbsp;&miunsminus;&nbsp;2)&nbsp;&times;&nbsp;(''m''&nbsp;&miunsminus;&nbsp;2).
 
== Example ==
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