Comment 9 for bug 1077912

Ok, great :) Is there a better place to report documentation errors than as bugs?

Martin

Den 13. nov. 2012 kl. 19:22 skrev Anders Logg <email address hidden>:

> I agree it may be confusing and I can clarify this in the
> documentation. But I would not call this a bug. It is a well-known
> feature that DirichletBC can be used to set "boundary conditions"
> anywhere. It's been like that for ca 10 years. That's also why we have
> the on_boundary parameter to allow setting conditions on the actual
> boundary.
>
> --
> Anders
>
>
> On Tue, Nov 13, 2012 at 10:40:04AM -0000, Martin Sandve Alnæs wrote:
>> 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.
>>>
>>>> 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