[petsc-users] Conditional Constraints

[Vijay S. Mahadevan]

> Do you want equality or inequality constraints? Equality constraints are
> naturally handled by writing a DAE.

I am looking at equality constraints only for now. But I just realized
that, the constraints in VI seem only to be on variables but not on a
function of it. So I guess the decoupled ODE+constraint might not have
worked.

On Sun, Jul 31, 2011 at 11:14 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> On Sun, Jul 31, 2011 at 22:11, Vijay S. Mahadevan <vijay.m at gmail.com> wrote:
>>
>> I saw from the documentation that the GL methods were capable of
>> handling DAE systems. But the intention of my question was about the
>> usage of the newton solver with functional constraints (with VI) for a
>> DAE since in a sense, the DAE systems are a composite of an ODE and a
>> constraint. So I was curious whether we could use temporal methods
>> that were not intended for DAEs but for stiff ODEs only and use the VI
>> solver to augment/restrict the solution with constraints. The reason
>> for this is due to the fact that in the creation of a stiff solver,
>> there are additional coefficient constraints that need to be satisfied
>> to be used for a DAE but this is less restrictive for solving ODEs.
>
> Do you want equality or inequality constraints? Equality constraints are
> naturally handled by writing a DAE. Inequality constraints would be handled
> by VI. VI is not currently available through TS, but my understanding is
> that Shri is looking into this and it will eventually be available there
> too.