[petsc-users] src/ksp/ksp/examples/tutorials/ex22.c

[Alexey Ryazanov]

Thank You!

2011/9/4 Matthew Knepley <knepley at gmail.com>

> On Sun, Sep 4, 2011 at 10:08 AM, Алексей Рязанов <ram at ibrae.ac.ru> wrote:
>
>> Hello!
>> Help me please to solve my tiny problem with dmmg.
>>
>> In the example src/ksp/ksp/examples/tutorials/ex22.c, which is discussed
>> on the 111th page of users manual, we use function
>> (line 36):
>> DACreate3d(PETSC_COMM_WORLD,DA_NONPERIODIC,DA_STENCIL_STAR,-3,-3,-3,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE,1,1,0,0,0,&da);
>> to "*create the DA that stores information about the coarsest grid you
>> wish to use*".
>> We can see that negative dimension values (-M, -N, -P) are used  "*to
>> indicate that it may be set to a different value from the command line with
>> -da_grid_x <M> -da_grid_y <N> -da_grid_z <P>". *
>> The question is: when I use -da_grid_ M,N,P options as the size of the
>> coarsest matrix, what's the size of the finest (most accurate, original
>> problem) matrix?
>>
>> I've tried to clear this up, using VecVew on the residual vector and
>> figured out, that when i'm using M,N,P as input parameters (so define the
>> coarsest grid as field of M*N*P dots), I get the residual vector of size
>> (4*M-3)*(4*N-3)*(4*P-3).
>> Is my result correct?  If yes, could you please explain why it happens in
>> this way.
>>
>
> When refinement happens, it adds a vertex between any two vertices,
> starting with the mesh you provide.
>
>    Matt
>
>
>> Sorry if my question is incorrect. I could mix up everything at all.
>> Thanks in advance!
>>
>> --
>> Best regards,
>> Alexey Ryazanov
>> ______________________________________
>> Nuclear Safety Institute of Russian Academy of Sciences
>>
>>
>>
>
>
> --
> 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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