[petsc-users] Convert MatNest to MatAIJ

Matthew Knepley knepley at gmail.com
Wed Oct 10 08:48:42 CDT 2012

On Wed, Oct 10, 2012 at 9:45 AM, Thomas Witkowski <
thomas.witkowski at tu-dresden.de> wrote:

>  You are right. But what if a have a MATNEST and i must convert it to
> MATAIJ. Any better way than what I wrote in my first mail?

I think you miss Jed's point. You should NEVER have a MATNEST. You should
have a Mat. Its type
should be determined by MatSetFromOptions(). If you want MATAIJ, you give
-mat_type aij, and if you
want MATNEST, you give -mat_type nest.



> Thomas
> Am 10.10.2012 15:33, schrieb Jed Brown:
> The best way, by far, is to assemble the matrix as AIJ if that is what you
> want to use. See MatGetLocalSubMatrix and SNES ex28. Using MATNEST should
> he a run-time choice.
> On Oct 10, 2012 8:30 AM, "Thomas Witkowski" <
> thomas.witkowski at tu-dresden.de> wrote:
>> Is there a fast way to convert a MatNest to a MatAIJ? I tried to use
>> MatConvert, but it seems that this convert is not yet implemented. As I
>> need this functionality to factorize the nested matrix with MUMPS, is there
>> any better way than to extract the nested matrices, iterate over all rows
>> of these matrices and use MatSetValues to add them again to the final
>> MatAIJ?
>> Thomas

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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