[petsc-users] Convert MatNest to MatAIJ

[Barry Smith]

On Oct 10, 2012, at 8:50 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> How did you get the MatNest?
> 
> What you describe is the right approach, but proper preallocation is messy in the general case. There is a partial implementation in petsc-dev, but it needs to be finished/debugged.

   Thomas,

      We should have a reasonable MatConvert_MatNest_MATAIJ. Perhaps you can look at what Jed has started in petsc-dev and improve it enough to suit your purpose.

    Barry




> 
> On Oct 10, 2012 8:45 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?
> 
> 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
>