Thank you for your answers.
First, I was wrong when telling that having empty rows is working for LU
solver: after verification, it is the exact opposite: it does not work
for MUMPS.
We have a nightly test that solve that kind of matrix with a
gmres+jacobi combination and it works well...
Second, since LU solvers are interesting to use as the solvers for the
coarsest level in a PCGAMG for example, we still have to give a non-zero
for all the diagonal...
So my solution will be to add it anyway... :)
Thanks again,
Eric
On 22/11/17 11:26 AM, Matthew Knepley wrote:
On Wed, Nov 22, 2017 at 11:13 AM, Eric Chamberland
<[email protected]
<mailto:[email protected]>> 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/[email protected]/msg22867.html
<https://www.mail-archive.com/[email protected]/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/>
