[petsc-users] Neumann BC with non-symmetric matrix

[Jed Brown]

Mark Adams <mfadams at lbl.gov> writes:

> I don't know.  Chombo/Boxlib have a stencil for C-F and do F-C with
> refluxing, which I do not linearize.  PETSc sums fluxes at faces directly,
> perhaps this IS symmetric? 

Depends on scaling.  Refluxing versus evaluating fluxes once on the fine
faces should give the same result.  Note that you can make a symmetric
FV discretization (for elliptic problems) by writing it as a mixed FE
method and choosing a quadrature so that fluxes can be eliminated.
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