[C]tot = 3, we have at the first iteration for the initial guess of e x = (1, 1, 1, 1, 1): Giving ||r|| = 2.74 and the approximate e x = (0.28, 0.58, 1.56, 0.09, 1.44) that can be used for the following iteration: . From a practical point of view, 16-digits precision may be unnecessary, so we can conveniently set up the algorithm for early stopping exploiting Eq. 13.