[petsc-users] Solving Poisson equation with multigrid

[Jed Brown]

Michele Rosso <mrosso at uci.edu> writes:

> Hi,
>
> I am successfully using PETSc (v3.3) in parallel to solve the Poisson 
> equation in 3D . 

Please upgrade to petsc-3.4 when you get a chance.

> The discretization is done by using finite difference on a uniform
> structured grid.  So far I used the conjugate gradient method, but I
> would like to give a try to multigrid.  The documentation describes
> multigrid as a preconditioner only, thus I would like to know if it is
> possible to use multigrid as a solver

  -ksp_type richardson

will not accelerate your multigrid.  Krylov with preconditioning is
almost never slower, and a lot more robust.

> and, if so, if you could give my some tips to start. 

  -pc_type mg -pc_mg_levels 3

  -pc_type gamg

  -pc_type ml

  -pc_type hypre