[petsc-dev] LSC question

[Jed Brown]

On Fri, Mar 9, 2012 at 11:05, Barry Smith <bsmith at mcs.anl.gov> wrote:

>    Here is the problem. We cannot use LSC with user provided L (and Lp)
> and PCFIELDSPLIT  now AT ALL!! That sucks, maybe we shouldn't be looking
> for a perfect solution but for now just one that works somewhat!
>

Yup, this is why I still have hacks that implement MatGetSubMatrix() to
pass this stuff around. I'll follow your suggestion here. How urgent is
this?


>
>
>    I will suggest the following approach. Attach various L to the original
> Jacobian with a different name for each. In your case L_displacement  and
> L_pressure, have PCFIELDSPLIT propagate them to the Schur matrix.  Then
> have  -prefixfromfieldsplit_pc_type lsc -prefixfromfieldplit_lsc_name
> L_displacement to tell LSC which one to use.
>
>   Barry
>
> Not perfect since the user could name the wrong lsc for the Schur index
> sets used but it is better than nothing.
>
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