[petsc-users] PCKSP

[Margarita Satraki]

Thank you very much Matt.

Margarita

On 19 June 2012 18:44, Matthew Knepley <knepley at gmail.com> wrote:

> On Tue, Jun 19, 2012 at 11:41 AM, Margarita Satraki <
> margarita.satraki at gmail.com> wrote:
>
>> If I understand correctly:
>>
>> For a system:
>> M^{-1} A x = M^{-1} b
>> we don't need to multiply M^{-1} A explicitly, but we solve M w = v
>> whenever needed.
>>
>> So the Krylov method is used in order to solve that system, or
>> equivalently to compute the vector M^{-1} v?
>>
>
> Yes
>
>    Matt
>
>
>>
>> On 19 June 2012 17:54, Matthew Knepley <knepley at gmail.com> wrote:
>>
>>> On Tue, Jun 19, 2012 at 10:33 AM, Margarita Satraki <
>>> margarita.satraki at gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> I have difficulty understanding how PCKSP works.
>>>>
>>>> From:
>>>>
>>>> http://www.mcs.anl.gov/petsc/documentation/tutorials/Columbia04/DDandMultigrid.pdf
>>>> I understand that instead of using preconditioners, it uses Krylov
>>>> methods for the ''inner solvers''.
>>>>
>>>> What are the ''inner solvers''? Is there some kind of a subsystem that
>>>> is solved instead of applying a preconditioner?
>>>>
>>>
>>> Nope, its jsut like a PC:
>>>
>>>   M^{-1} A x = M^{-1} b
>>>
>>> where now M^{-1} instead of being an LU solve, for instance, is a Krylov
>>> solve.
>>>
>>>    Matt
>>>
>>>
>>>> Many thanks,
>>>>
>>>> Margarita
>>>>
>>>
>>>
>>>
>>> --
>>> 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
>
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