[petsc-users] How can I retrieve the IS for all Missing Diagonal entries?

[Matthew Knepley]

On Wed, Nov 22, 2017 at 11:13 AM, Eric Chamberland <
Eric.Chamberland at giref.ulaval.ca> wrote:

> Hi,
>
> I have 2 questions:
>
> First, I am looking for a function that is almost like MatMissingDiagonal,
> but that would return me *all* missing diagonal entries.
>
> Does it exists?
>

No


> If not, is there another way of doing this?
>

Not a nice way, unfortunately. It is fairly dependent on the
implementation. You could call GetRow() for every row and check.


> Second: after searching through Petsc list, I found this that upset me a
> bit:
>
> https://www.mail-archive.com/petsc-users@mcs.anl.gov/msg22867.html
>
> so maybe I should modify our code to be fully compliant with this?  I have
> some examples (MUMPS) that are working without diagonal entries but I
> didn't tried other PCs or KSPs...
>

We use the diagonal frequently, for instance in the factorization PCs. I am
guessing we put in the diagonal when converting to the MUMPS format.

  Thanks,

    Matt


> Thanks,
>
> Eric
>



-- 
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.caam.rice.edu/~mk51/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20171122/f2d33185/attachment.html>