[petsc-dev] MatNest and FieldSplit

[Pierre Jolivet]

It’s a 4x4 matrix.
The first 2x2 diagonal matrix is a field.
The second 2x2 diagonal matrix is another field.
In the second field, the first diagonal coefficient is a subfield.
In the second field, the second diagonal coefficient is another subfield.
I’m changing the operators from the second subfield (last diagonal coefficient of the matrix).
When I solve a system with the complete matrix (2 fields), I get a different “partial solution" than when I solve the “partial system” on just the second field (with the two subfields in which I modified the operators from the second one).

I don’t know if this makes more or less sense… sorry :\
Thanks,
Pierre

> On 24 Mar 2019, at 8:42 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Sat, Mar 23, 2019 at 9:12 PM Pierre Jolivet via petsc-dev <petsc-dev at mcs.anl.gov <mailto:petsc-dev at mcs.anl.gov>> wrote:
> I’m trying to figure out why both solutions are not consistent in the following example.
> Is what I’m doing complete nonsense?
> 
> The code does not make clear what you are asking. I can see its a nested fieldsplit.
> 
>   Thanks,
> 
>      Matt
>  
> Thanks in advance for your help,
> Pierre
> 
> 
> 
> -- 
> 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.cse.buffalo.edu/~knepley/>

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