> 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
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
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,