Re: [Libmesh-users] Initial mesh with hanging nodes

[Roy S. <roy...@ic...>]

On Sat, 3 Feb 2018, Laura Scarabosio wrote:

> I apologize for the simple question but I could not find satisfactory answers 
> on the web.

I'm not surprised; I think the most relevant discussion was just a
week ago:

https://sourceforge.net/p/libmesh/mailman/message/36202144/

and even if we managed to hit whatever keywords you were searching
for, it probably doesn't get ranked highly by search engines yet.

> Does libMesh support meshes with hanging nodes when these are used right away 
> and do not come from a libMesh refinement of a mesh without hanging nodes?
> I mean, is calling dof_map.constrain_element_matrix_and_vector enough to 
> handle this case, too?

It depends what you mean by "used right away":

If the hanging nodes come from a libMesh-*style* refinement (isotropic
refinement of a parent element), then libMesh will auto-generate
constraint equations for them, even if you're just loading the refined
mesh from a saved or handwritten file rather than using libMesh
refinement code.

However, if the hanging nodes don't fit the pattern of "coarse
element with isotropically refined neighbor", libMesh will not
auto-generate constraint equations.  You could still define systems on
such a mesh, but you'd have to add constraint equations manually to
get solves to work, you'd have to add ghosting functors to get
DistributedMesh to work, you'd have to add jump terms to error
estimators by hand, and in general it would be a huge pain in the
neck.
---
Roy