There is no harm in having the GMRES there even if you use a direct solver
(for testing) so just leave the GMRES. Changing to preonly every time you try
LU is prone to error if you forget to change back.
Barry
> On May 22, 2019, at 2:45 PM, Sajid Ali via petsc-users
> wrote:
>
> Hi
> On May 22, 2019, at 2:26 PM, Sajid Ali via petsc-users
> wrote:
>
> Hi Hong,
>
> Looks like this is my fault since I'm using -ksp_type preonly -pc_type gamg.
> If I use the default ksp (GMRES) then everything works fine on a smaller
> problem.
>
> Just to confirm, -ksp_type preonly
Hi Matt,
Thanks for the explanation. That makes sense since I'd get reasonably close
convergence with preonly sometimes and not at other times which was
confusing.
Anyway, since there's no pc_tol (analogous to ksp_rtol/ksp_atol, etc), I'd
have to more carefully set the gamg preconditioner
Hi Hong,
Looks like this is my fault since I'm using -ksp_type preonly -pc_type
gamg. If I use the default ksp (GMRES) then everything works fine on a
smaller problem.
Just to confirm, -ksp_type preonly is to be used only with direct-solve
preconditioners like LU,Cholesky, right ?
Thank You,
