Manav Bhatia <bhatiama...@gmail.com> writes: > I also observed that the number of KSP iterations increases with an increase > in the levels of AMG. Is this true, in general, for all/most applications?
Adding levels replaces a direct solve with a deeper V-cycle. When MG is behaving well, this makes little difference because the coarse approximations are no worse than the approximations made in the first coarsening (from fine level to first coarsened level). But there are many stubborn problems for which it does hurt, as you have seen.
