[petsc-users] Ksp Null space

[Matthew Knepley]

On Mon, May 16, 2011 at 5:54 PM, Ataollah Mesgarnejad <
amesga1 at tigers.lsu.edu> wrote:

> Dear Barry,
>
> In that example the basis for null space is empty(only constant null
> space). I was wondering how would I form a Vec for example a for a 2D null
> space?
> Specifically I'm trying to remove a null space that its span(C,x,y) in my
> 2D matrix that I form using DA?
>

Do you mean the null space is translations in x and y? Then you give two
vectors, the first with 1s in the first component,
and the second with 1s in the second component. These can be easily made
using DAVecGetArrayDOF.

   Matt


> Best,
> Ata
>
> On Mon, May 16, 2011 at 2:02 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>  src/ksp/ksp/examples/tests/ex20.c
>>
>>  Note that this is not a good example from the point of view of efficient
>> generation of the matrix and solution of the linear system but it does
>> demonstrate these functions
>>
>>   Barry
>>
>>
>> On May 16, 2011, at 12:39 PM, Ataollah Mesgarnejad wrote:
>>
>> > Dear all,
>> >
>> > Does anyone know of any example programs that use MatNullSpaceCreate and
>> KSPsetNullSpace routines?
>> >
>> > Best,
>> > Ata
>>
>>
>
>
> --
> A. Mesgarnejad
> PhD Student, Research Assistant
> Mechanical Engineering Department
> Louisiana State University
> 2203 Patrick F. Taylor Hall
> Baton Rouge, La 70803
>



-- 
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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