[petsc-users] Is PCMG a generic PC object ?

[Vijay S. Mahadevan]

Matt, I have used the Hypre AMG option in the past but have not tried
ML AMG before. Are there any added advantages in terms of
performance/memory footprint and such between the two ?

Vijay

On Fri, Dec 3, 2010 at 12:36 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Fri, Dec 3, 2010 at 12:33 PM, Randall Mackie <rlmackie862 at gmail.com>
> wrote:
>>
>> Are there any examples that show how to use the ML PC?
>
> -pc_type ml
> It is Algebraic Multigrid.
>    Matt
>
>>
>> Randy
>>
>> On Dec 3, 2010, at 9:02 AM, Matthew Knepley wrote:
>>
>> I will also note that a good intro for implementing your own might be the
>> ML PC
>> in Petsc. It puts the ML AMG package into the PCMG framework.
>>    Matt
>>
>> On Fri, Dec 3, 2010 at 3:44 AM, Dave May <dave.mayhem23 at gmail.com> wrote:
>>>
>>> Hey Vijay,
>>>  PCMG is generic. If you provide the operators for each level, along
>>> with the restriction and prolongation,
>>> you can use PCMG. It doesn't need to know about the mesh.
>>>
>>> You don't actually need to provide the coarse grid operators.
>>> Given the fine grid operator and R and optionally P, you can use
>>> Galerkin coarsening by calling
>>> PCMGSetGalerkin() or via the command line arg -pc_mg_galerkin
>>> Also, if you don't specify the prolongation, petsc will use P = R^T.
>>>
>>>
>>> Cheers,
>>>  Dave
>>>
>>>
>>> On 3 December 2010 06:02, Vijay S. Mahadevan <vijay.m at gmail.com> wrote:
>>> > Hi all,
>>> >
>>> > I was wondering whether the MG preconditioner object is generic enough
>>> > to work out of the box like say ILU or SOR.  To elaborate on this, if
>>> > I can provide the number of levels, restriction and prolongation
>>> > operators for each level and the system operators along with vectors
>>> > allocated for solution and rhs, would it work as a preconditioner for
>>> > my given problem and a prescribed rhs at the finest level of PCMG. Or
>>> > does it need some knowledge of the fine and coarser meshes to perform
>>> > the MG operations correctly ?
>>> >
>>> > All the examples I've seen using MG in petsc involve the DA and DMMG
>>> > objects and since I use my own mesh and corresponding discretization
>>> > code for an elliptic system, I'm curious about this usage. It would
>>> > not be terribly difficult to write my own framework to do a simple
>>> > V-cycle with my existing framework but since petsc already provides
>>> > this functionality along with different types of MG solves (with
>>> > verified code!), I really want to use it for my system. Any help
>>> > and/or pointers are welcome.
>>> >
>>> > Thanks,
>>> > vijay
>>> >
>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener
>