[petsc-users] Fwd: MatZeroRowsColumns for mpibaij

[Stephan Kramer]

On 01/11/13 06:01, Matthew Knepley wrote:
> On Wed, Oct 30, 2013 at 9:19 PM, Rhodri Davies <rhodri.davies at anu.edu.au <mailto:rhodri.davies at anu.edu.au>> wrote:
>
>     Dear all,
>
>     Would you mind giving us an update on your thoughts re: this question? We're very keen to be able to use such functionally and it would be good to know if you're looking into this / have any
>     suggestions?
>
>
> I looked at the code. It does not look hard to make a MPIBAIJ version. Since the scatter context for BAIJ is already exploded, most
> of the MPIAIJ code goes straight through, it just a matter of handling the blocking in a few places.
>
> Here is what would be really helpful for us. Write a nice test. The code would probably only take an hour of being careful. However,
> the test assembly would be more. If you give us a nice test example for it, writing it could happen pretty quickly.
>
>    Thanks,
>
>      Matt

That would be great. I had a look at the existing tests and found src/mat/examples/tests/ex140.c which already claims to test MatZeroRowsColumns with MPIBAIJ - except it isn't being run in parallel. 
Would running this test in parallel be a sufficient test to work with? It currently fails with the expected message "No support for this operation for this object type!". I'd be happy to write another 
test but it would basically be creating another matrix and testing it does the right thing with the matrix and the rhs. Let me know if there's anything else we could help out with

Cheers
Stephan

>> From: Stephan Kramer <s.kramer at imperial.ac.uk>
>> Subject: Fwd: [petsc-users] MatZeroRowsColumns for mpibaij
>> Date: 31 October 2013 13:16:05 GMT+11:00
>> To: Rhodri Davies <rhodri.davies at anu.edu.au>
>>
>>
>>
>>
>> -------- Original Message --------
>> Subject: [petsc-users] MatZeroRowsColumns for mpibaij
>> Date: Wed, 19 Jun 2013 13:22:31 +0100
>> From: Stephan Kramer <s.kramer at imperial.ac.uk>
>> To: PETSc users list <petsc-users at mcs.anl.gov>
>>
>> Dear all,
>>
>> We have found the MatZeroRowsColumns() routine to be very useful for lifting boundary conditions. Unfortunately we also found that it isn't implemented for matrix type mpibaij and we're quite keen on
>> keeping the baij structure as it seems to give us significant savings for DG problems (in particular the blocked sor). I had a quick look at the implementation of MatZeroRowsColums_MPIAIJ but couldn't
>> really estimate how hard it would be to do something similar for mpibaij (an implementation for seqbaij exists already). Is this something that's likely to be looked at in the future?
>>
>> Stephan