# Generating Gauss-Seidel hard system

I am writing various Gauss-Seidel algorithm parallel implementations using different programming techniques for my assignment.

I have created a MATLAB script for generating strictly diagonally dominant matrices with different degree of diagonal dominance and sparseness for testing my implementations.

Problem is that I can't find a way to generate matrix that requires more than 15 iterations to converge (epsilon is set to 0.0001).

Is there a property that makes a system GS-hard?

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Probably you should consider asking this on SciComp. However, I would probably suggest looking at spectral properties including Condition Numbers. –  Inquest Mar 17 '12 at 20:04
If you mention the Hilbert matrix, people will think that you know what you are talking about. –  marty cohen Mar 18 '12 at 4:54