On Mon, 27 May 2013 23:32:12 +0100
"Garth N. Wells" <[email protected]> wrote:
> On Monday, 27 May 2013, Jan Blechta wrote:
> 
> > On Mon, 27 May 2013 23:10:47 +0100
> > "Garth N. Wells" <[email protected] <javascript:;>> wrote:
> > > On 27 May 2013 22:06, Jan Blechta
> > > <[email protected]<javascript:;>>
> > wrote:
> > > > How do I obtain FacetFunction
> > > >   fd = mesh.domains().facet_domains()
> > > > with redesigned MeshDomains?
> > > >
> > >
> > >   D = mesh.topology().dim()
> > >   fd = mesh.domains().markers(D - 1)
> > >
> > > 'fd' is now not a MeshFunction (std::map from C++ and a dict on
> > > the Python side). It was necessary to change the type to remove a
> > > circular dependency that was making new developments
> > > exponentially more complicated and to make memory management
> > > robust. A lot of boilerplate code was removed.
> > >
> > > If it turns out that a MeshFunction is required, we could add a
> > > MeshFunction constructor to make it simple to make a MeshFunction.
> >
> > Indeed, MeshFunction is needed to feed DirichletBC or Measure.
> 
> 
> You can create Dirichlet bcs that use the domain markers without
> accessing the domain markers directly. See test_meshdomain_bcs in:
> 
> https://bitbucket.org/fenics-project/dolfin/src/1247bb468d88885d57abbe74cbb82984818eacfd/test/unit/fem/python/DirichletBC.py?at=master

You're right here. But other use cases:
  - Measure
  - output to file
  - computations of other mesh functions

The last point is easily solved but others, I think, not. Such a
constructor will enable users to adapt working code with 2 line patch.
So I filed an issue.

Jan

> 
> Garth
> 
> 
> 
> > Jan
> >
> > >
> > > Garth
> > >
> > > > Jan
> > > > _______________________________________________
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> 
> 

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