[petsc-users] Conditional Constraints

[Jed Brown]

On Sun, Jul 31, 2011 at 22:24, Vijay S. Mahadevan <vijay.m at gmail.com> wrote:

> I am looking at equality constraints only for now.
>

VI stands for Variational Inequality. It wouldn't make sense to use for
equality constraints. Just write your system as a DAE.


> But I just realized
> that, the constraints in VI seem only to be on variables but not on a
> function of it.
>

That just means you have to introduce new variables.

Maybe others can comment on this, but I suspect that, as with DAEs, the
well-behaved system that you eventually want to solve might come after
eliminating those intermediate variables. For DAEs, we just changed the
formalism slightly so the user (and any Jacobian information that they might
provide) works with a form in which the extra variables have been
eliminated. If that is the case, we should look at the API to see if we can
hide the intermediate variables from the user (thus letting them set
constraints on arbitrary functions of the independent variables).
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