Re: [Libmesh-devel] Contraints for JFNK hanging nodes and Dirchlet BC's

[Derek G. <der...@in...>]

On Oct 31, 2008, at 2:00 PM, Benjamin Kirk wrote:

> I use it to extract element-based Dofs, and they get properly  
> constrained.
> Would the residual value then be the current value - the constraned  
> value,
> as you mention?

I didn't know that method existed.  It looks like it's pretty much  
achieving the same goal that enforce_constraints_exactly() does.... it  
at least means that you are calculating your next residual using the  
properly constrained value.

Unfortunately, this doesn't help with calculating a constrained  
value.  For instance, let's say that on solve #23 your solver decides  
it's converged... and libMesh writes out the solution.  Do you have  
any idea what the value of your solution at the hanging nodes is?   
Unless you called enforce_constraints_exactly() before you wrote out  
the solution.... you don't.

One idea would be for me to overwrite my own residual before I add it  
into the global residual.... I guess I could call is_constrained() on  
every node on the element and if it is then I could overwrite what  
residual is there with u - constrained_value before I add it in.....  
this is essentially the work I was thinking  
constrain_element_residual() would do.

Derek