[petsc-users] Convergence of AMG

[Manav Bhatia]

Thanks! 

> On Oct 29, 2018, at 1:03 PM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Manav Bhatia <bhatiamanav at 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.