“…On the other hand, results are less sensitive to the minimum eigenvalue estimate, provided λ min > 0, as this delimits between the low frequencies that are handled by the coarse grid correction and the high frequencies that are eliminated by the action of the smoother. The choice of the bounds (relative to λ) is not universal: (1/30,1.1) [1], (0.3,1) [2], (0.25,1) [28], and (1/6,1) [32] have all been considered. Based on the results of Table 1, we set (λ min , λ max ) = (0.1, 1.1) λ as a conservative choice.…”