[petsc-dev] controlling vector values while doing matrix free operations

[Jed Brown]

On Wed, Dec 14, 2011 at 19:31, Barry Smith <bsmith at mcs.anl.gov> wrote:

> If you are truly near 0 in temperature or pressure and differencing can
> push you over the limit then I submit it is perfectly reasonable to solve
> them as VI.
>

Note that this tends to grow the algebraic systems quite a bit. Usually
such problems are solved in conservative variables (density, momentum,
energy), but the more troublesome constraints (pressure, temperature) are
nonlinear functions of the conservative variables. As currently
implemented, you would have to solve (density, momentum, energy, pressure,
temperature) in order to impose those constraints with SNESVI. I wonder if
there is a way to eliminate these constraints earlier so that the systems
don't grow so much.
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