[petsc-dev] Semismooth Newton

Jed Brown jedbrown at mcs.anl.gov
Tue Jul 31 02:36:32 CDT 2012

On Mon, Jul 30, 2012 at 5:40 PM, Todd Munson <tmunson at mcs.anl.gov> wrote:

> > 1. change SNESVI to support general complementarity constraints because
> only doing box constraints on state variables is lame
> Okay; and how do you want to do this?  You need to write out the
> corresponding KT system
> and then you just have a box constrained problem.  One can make it easier
> to write the
> KT system, but then you have to precondition the KT system.

Yes, but if the user created the augmented system, they have to inform the
linear solver of that structure. I think it is much more convenient for the
user to not have to manage those things.

> There are some reformulations for polyhedral constraints, but they are, in
> my opinion,
> a bit unwieldy.

Why unwieldy?

Note that changing the size of the constrained size is also important, and
box constraints strike me as even more confusing in that context.

> > 2. have a mode to solve the system in the full space, instead of
> eliminating the semi-smooth variables (which produces the bad conditioning)
> There are all these options in the TAO methods.
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