[petsc-users] Nested Fieldsplit for custom index sets

[Lawrence Mitchell]

> On 27 Jul 2016, at 03:54, Safin, Artur <aks084000 at utdallas.edu> wrote:
> 
> Barry,
> 
>> Do you have a call to KSPSetFromOptions() before the call PCFieldSplitGetSubKSP()? I am guessing not which means that the PC does not yet know that it is of type fieldplit.
> 
> Yes, I call KSPSetFromOptions() for the global matrix at the beginning of the code. Should I also do it for the ksp I obtain from PCFieldSplitGetSubKSP()?
> 
> The program has no problem doing fieldsplit for the global matrix; my issue is that I cannot get it to recognize a fieldsplit within a fieldsplit.

I think the SubKSPs (and therefore SubPCs) are not set up until you call KSPSetUp(ksp) which your code does not do explicitly and is therefore done in KSPSolve.

Cheers,

Lawrence
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