This is a very simple Pascal program I wrote in mid 1990s, which solves a sparse NxN linear system using the Succesive Overrelaxation Method (SOR), which in turn is based on Gauss Seidel Method.
Both methods are iterative.
N is initially set at maximum …64.
You need the W factor for the SOR to complete successful. The theory assures us that it must be W=1.062.