[petsc-users] Help with ML/BoomerAMG

[Jed Brown]

Gaetan Kenway <gaetank at gmail.com> writes:

> Hi Jed
>
> This problem was external  flow, transonic Euler, (M=0.85), conserved
> variables.  As I stated in my email, the additive schwartz method + (block)
> ILU on the subdomains works extremely well for this problem. The real
> problem I am interested in however, is preconditioning for the RANS
> equations. For the most  part, ASM+ILU works fine for these problems as
> well, but I am investigating other methods that may potentially increase
> robustness/reduce memory/reduce  computational cost.

ASM/ILU is pretty much the workhorse method for those not using
geometric multigrid.

> Since the solver I'm using is a structured multiblock solver that  uses
>  multigrid for the primal  problem, I can use geometric  multigrid,
> provided I construct the restriction and prolongation operators myself.
>
> I guess geometric multigrid is  the best approach here.

Yes, and the adjoint problem should be faster than the forward problem
because it's linear.  Are you using FAS or linear MG for the forward
problem?

Is this a steady-state solve?