[petsc-users] Help with ML/BoomerAMG

[Jed Brown]

Gaetan Kenway <gaetank at gmail.com> writes:

> For the forward solve I use ASM+ILU in the same manner as for the adjoint
> problem.
> The  ASM not a bottleneck  per se. Typically we see the  adjoint problem
> taking the same amount of time as the non-linear problem for well-behaved
> flows, and the adjoint is shorter for  less well-behaved flows.

Sounds reasonable.

> The real problem I am having is for certain RANS cases, the
> frozen turbulence adjoint is extremely difficult to solve --- requiring
>  GMRES subspace sizes on the order of 400-500 to converge.

Hmm, which turbulence model are you using?  Is it related to stretched
grids?  Continuous or discrete adjoint?