Comment 7 for bug 1077912

Boundary (topology), the closure minus the interior of a subset of a topological space; an edge in the topology of manifolds, as in the case of a 'manifold with boundary'

As I said above, this is at the very least a documentation bug. The sentence I quote makes no sense when all facets may be considered on the boundary. I.e. "a facet that is entirely on the boundary". An alternative interpretation of what "boundary" means also does not match the on_boundary argument to subdomain.inside. And BoundaryMesh takes the exterior boundary. Right? So some clarification of terms is in order, at least in the DirichletBC documentation.

Martin

Den 13. nov. 2012 kl. 10:12 skrev Anders Logg <email address hidden>:

> This is not a bug. The problem is the interpretation of what boundary
> means. The boundary is whatever the user specifies and it can lie in
> the interior.
>
> --
> Anders
>
>
> On Mon, Nov 12, 2012 at 12:26:54PM -0000, Martin Sandve Alnæs wrote:
>> Public bug reported:
>>
>> According to
>>
>> http://fenicsproject.org/documentation/dolfin/1.0.0/python/programmers-
>> reference/fem/bcs/DirichletBC.html#dolfin.fem.bcs.DirichletBC
>>
>> "The topological approach is faster, but will only identify degrees of
>> freedom that are located on a facet that is entirely on the boundary."
>>
>> However, this does not seem to be the case. I will attach here a code
>> which changes behaviour when switching between marking all facets or all
>> facets on the boundary, look for the lines:
>>
>> if enable_bug:
>> boundaries.set_all(walldomain)
>> else:
>> Wall().mark(boundaries, walldomain)
>>
>> ** Affects: dolfin
>> Importance: Undecided
>> Status: New
>>
>
> --
> You received this bug notification because you are a member of DOLFIN
> Core Team, which is subscribed to DOLFIN.
> https://bugs.launchpad.net/bugs/1077912
>
> Title:
> Incorrect DirichletBC behaviour applying to interior facets
>
> Status in DOLFIN:
> New
>
> Bug description:
> According to
>
> http://fenicsproject.org/documentation/dolfin/1.0.0/python
> /programmers-
> reference/fem/bcs/DirichletBC.html#dolfin.fem.bcs.DirichletBC
>
> "The topological approach is faster, but will only identify degrees of
> freedom that are located on a facet that is entirely on the boundary."
>
> However, this does not seem to be the case. I will attach here a code
> which changes behaviour when switching between marking all facets or
> all facets on the boundary, look for the lines:
>
> if enable_bug:
> boundaries.set_all(walldomain)
> else:
> Wall().mark(boundaries, walldomain)
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/dolfin/+bug/1077912/+subscriptions