[petsc-users] TS algo question

[Jed Brown]

Mark Adams <mfadams at lbl.gov> writes:

> I have setup the equations attached using TSSetIJacobian and
>  TSSetIFunction.
>
> This is intended to be a fully implicit solvers with some auxiliary
> variables.
>
> We want to verify the code with the current forward Euler solver.  

Mark, this is a DAE, so your "forward Euler" solver cannot literally be
forward Euler.  It can be a semi-implicit method with differential
variables propagated using forward Euler combined with solves at some
point.  If you want flexibility in treating terms implicitly and
explicitly, define both the RHSFunctian and IFunction.  Put those you
want to treat implicitly in the IFunction.  (And make the IJacobian the
Jacobian of the IFunction).
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