[petsc-users] Suggestions for code with dof >> 1 ?

[Jed Brown]

Christophe Ortiz <christophe.ortiz at ciemat.es> writes:
> I found where is the problem. I had
> set TSARKIMEXSetFullyImplicit(ts,PETSC_TRUE);
> I found it produces wrong solutions, either with ARKIMEX3, 1BEE or A2.
> Solution becomes negative. Without this option, all ARKIMEX types work very
> well and very fast.

I'm glad they work as IMEX methods (please check that the solutions are
correct), but I would like to find out why they are not working in fully
implicit mode.  Is your problem similar to ex25?  (If I remember
correctly, that example uses a DAE formulation for boundary conditions
and thus has trouble with some methods with explicit stages.  There may
be more going on.)
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