# What really means when the teacher asks me to iterate on Gauss-Seidel considering a maximum variation of 0.01?

My teacher has a problem that asks me to iterate on Gauss-Seidel equations considering a maximum variation of 0.01. This means making the first iteration and get check if the max of each error is less that 1%?

err(x1) = (actual-guess)/actual = 100%
err(x2) = 100%
err = max(err(x1), err(x2))


Need another iteration because the err > than requested. Is this what it really means?

thanks

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Don't think so. In real life, you never know what the true answer to your problem is (call it $x^*$ for convenience). In practice, you use deviation from the previous iterate as a stopping criterion. So instead of computing error as $|x_n - x^*|$, use $|x_n - x_{n-1}|$.
@Totty depending on the problem, you may want to use absolute error calculation (as in my answer) or relative error calculation (as you are suggesting, $|1 - x_n/x_{n-1}|$). Both are measures of how far the last step moved away from the previous one. The idea is, when convergence happens, iteration step size decreases... –  gt6989b Feb 21 '13 at 15:27