[petsc-users] Modifying Entries Tied to Specific Points in Finite Element Stiffness Matrix using DMPlex

[Matthew Knepley]

On Thu, Dec 8, 2022 at 6:06 PM Hongrui Yu <yuhongrui at utexas.edu> wrote:

> Hello! I’m trying to adapt a serial Finite Element code using PETSc. In
> this code it reads in special stiffness terms between the boundary DoFs
> from an input file, and add them to corresponding locations in the global
> Jacobian matrix.
>

Hmm, so in completely general locations, or on the diagonal?


> I currently use a DM Plex object to store the mesh information. My
> understanding is that once the DM is distributed its points are renumbered
> across different ranks.
>

That is true.


> I wonder if there is a good way to find the corresponding entries that
> needs to be modified in the global Jacobian matrix?
>
>
>
> For Vectors I’m currently creating a Natural Vector and simply do
> DMPlexNaturalToGlobal. Is there a way to create a “Natural Mat” just like
> “Natural Vector” and then do some sort of NaturalToGlobal for this Mat?
>
>
>
> Any help would be highly appreciated!
>

If it is completely general, this will take some coding.

  Thanks,

     Matt


> Kevin
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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