[petsc-users] DMDA and vector PDE

[Matthew Knepley]

On Tue, Nov 1, 2011 at 4:13 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Tue, Nov 1, 2011 at 10:06, Alexander Grayver <agrayver at gfz-potsdam.de>wrote:
>
>> Thanks Jed, looks easy. I've read about this parameter in documentation,
>> but it wasn't obvious how to use it.
>> May be it's worth to mention it shortly in "2.4.4 Accessing the Vector
>> Entries for DMDA Vectors" or somewhere else.
>>
>
> I'll add a note. The most common approach is to declare a struct
>
> typedef struct {
>     PetscScalar u,v,omega,temp;
> } Field;
>
> and then access as x[j][i].omega, etc. An example:
>
>
> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/src/snes/examples/tutorials/ex50.c.html
>

Or you can use


http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/DM/DMDAVecGetArrayDOF.html

and access it as x[j][i][0-3].

   Matt

-- 
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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