[petsc-users] Solving Poisson equation with multigrid

[Jed Brown]

Matthew Knepley <knepley at gmail.com> writes:

> It looks like you are running in parallel (never do this until everything
> works in serial), which probably means you are using
> PCREDUNDANT for the coarse PC, so you need what Jed suggested:
>
>   -mg_coarse_sub_pc_type svd

GAMG uses block Jacobi by default, not redundant.  If it was redundant,
you would use -mg_coarse_redundant_pc_type svd.