[petsc-users] MATNEST with shell matrices

[Matthew Knepley]

On Thu, Feb 21, 2013 at 5:19 PM, Amneet Bhalla <mail2amneet at gmail.com>wrote:

> Can you guys comment on what example case would be best to start off for
> shell
> operators with FieldSplit? The examples I am looking into all start with
> creating native
> PETSc matrices and vectors.
>
> If possible could you write down steps that would be needed in setting
> such system...
>
> a) Create matrices using XXXX (?) b) Create vectors using YYYY ....
>

1) Solve your system with a standard KSP solver, like GMRES

2) Tell PCFIELDSPLIT about your fields using PCFieldSplitSetIS(),
http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/PC/PCFieldSplitSetIS.html

Now you are ready.

    Matt


> On Thu, Feb 21, 2013 at 3:24 PM, Matthew Knepley <knepley at gmail.com>wrote:
>
>> On Thu, Feb 21, 2013 at 4:20 PM, Amneet Bhalla <mail2amneet at gmail.com>wrote:
>>
>>>
>>> On Thu, Feb 21, 2013 at 2:57 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>>
>>>> that you're happy with and that performs well with fieldsplit or custom
>>>> preconditioning that will be amenable to your MatShells
>>>
>>>
>>> Is fieldsplit an alternative approach to MatNest and VecNest? The
>>> problem is that I am working on nonnative PETSc
>>> data; so I am not sure which recent methods would support shell
>>> approach. All I want is to use PETSc's algorithm
>>> for solving multicomponent system of equation. I am not bothering about
>>> preconditioning yet, as I will be trying
>>> a custom preconditioner down the road.
>>>
>>
>> MatNest is just an optimization matrix format. Get your stuff working
>> with FieldSplit and then think about optimization.
>>
>>    Matt
>>
>>
>>>
>>> --
>>> Amneet
>>>
>>>
>>>
>>>
>>
>>
>> --
>> 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
>>
>
>
>
> --
> Amneet
>
>
>
>


-- 
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
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