On Tue, Sep 11, 2012 at 11:44 AM, Roy Stogner <roystgnr@ices.utexas.edu> wrote:

On Tue, 11 Sep 2012, Derek Gaston wrote:

> One of our users is looking for the ability to do Periodic BCs... but where instead of have _equality_ on either side of the periodic boundary you
> instead have a constant offset.
> So if u_i is periodic with u_j you would then have the constraint that u_j = u_i + c ... where c is that specified offset.
> What's really tricky is that they want a different constant value for each variable.
> Anyone see a way to make that happen?

It'd actually be pretty easy now that the heterogenous constraints are
in - we'd just want to add "offset" values to the PeriodicBoundary
class and respect that when constructing the constraint equations.

The main problem is: isn't the new PBC code still failing some of your
tests?  Last I heard, John still had a MOOSE regression test breaking
but hadn't been able to distill it down into a libMesh-only failure
case to send me.

So we do still have one test that's failing.  John coded up the example in pure libMesh code and it works so the problem doesn't appear to be on your end.  However there are a few differences in the way MOOSE solves it and Johns example: for one we solve every problem with a transient nonlinear system using JFNK which is of course different from the simple example John has already coded up using a linear system.  We were down to looking at differences in the system matrix to try to figure out why things were different, but will need more time to narrow down the issue.

I think we've decided that we are going to put this one problem to the side for now since it has been a hefty time sink and move forward until we have some more downtime.  The remaining PBCs issues appear to be solved using your latest (uncommitted?) patch.  We are going to work on updating all of our users to the current head of libMesh barring any other issues.  Thanks for working on this for us!


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