[petsc-dev] Mark, what's the rational for keeping the Chebyshev tuning inside GAMG?

Mark Adams mfadams at lbl.gov
Wed Feb 25 10:20:59 CST 2015

> We could make what you have (finding rows with just diagonals) the
> default.  For, e.g., vector-valued problems with unaligned partial
> Dirichlet conditions, the user could specify something else.

Sure.  But unaligned BCs are fine.  This problem just comes from users
doing something stupid from our perspective (and not innately stupid) and
putting a "big" fake number on the diagonal for the BC.

Note, unaligned BCs require the null space be adjusted accordingly so my
syntactic sugar (that Jed hates) of taking coordinates and doing this for
users is not quite correct.  Bit probably does not matter at BCs in
practice anyway.
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