dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Friday 19 December 2008 11:01:08 Martin Sandve Alnæs wrote:
> On Fri, Dec 19, 2008 at 10:55 AM, Johan Hake <hake@xxxxxxxxx> wrote:
> > On Friday 19 December 2008 10:08:40 Kristian Oelgaard wrote:
> >> Quoting Johan Hake <hake@xxxxxxxxx>:
> >> > On Thursday 18 December 2008 22:34:14 Anders Logg wrote:
> >> > > On Wed, Dec 17, 2008 at 11:42:47PM +0100, Johan Hake wrote:
> >> > > > On Wednesday 17 December 2008 22:57:48 Anders Logg wrote:
> >> > > > > On Wed, Dec 17, 2008 at 10:53:32PM +0100, DOLFIN wrote:
> >> > > > > > One or more new changesets pushed to the primary dolfin
> >> > > > > > repository. A short summary of the last three changesets is
> >> > > > > > included below.
> >> > > > > >
> >> > > > > > changeset:   5406:bc43cc830c11058dcabf239a5a7f878bb860fabb
> >> > > > > > tag:         tip
> >> > > > > > user:        Anders Logg <logg@xxxxxxxxx>
> >> > > > > > date:        Wed Dec 17 22:53:27 2008 +0100
> >> > > > > > files:       TODO demo/la/eigensolver/python/demo.py
> >> > > > > > demo/pde/optimization/python/demo.py description:
> >> > > > > > Fix remaining unchecked demos. Some demos still broken:
> >> > > > > >
> >> > > > > >   EE demo/pde/nonlinear-poisson/python/demo.py
> >> > > > > >   EE demo/pde/poisson1D/python/demo.py                   
> >> > > > > > viper problem with 1D EE demo/pde/waveguide/python/demo.py
> >> > > > > >
> >> > > > > >   results in C++ and Python differ EE
> >> > > > > > demo/pde/dg/advection_diffusion/python/demo.py
> >> > > > > >   EE demo/nls/nonlinearpoisson/python/demo.py
> >> > > > > >   EE demo/mesh/partitioning/python/demo.py
> >> > > > > >   EE demo/mesh/intersection/python/demo.py               
> >> > > > > > strange transformation EE
> >> > > > > > demo/ode/aliev-panfilov/python/demo.py EE
> >> > > > > > demo/ode/lorenz/python/demo.py
> >> > > > >
> >> > > > > We may ignore the ODE demos here. Some work is needed to get the
> >> > > > > ODE solvers to function from Python but they have only worked in
> >> > > > > part before so it's not very important now.
> >> > > > >
> >> > > > > The following demos remain:
> >> > > > >
> >> > > > >    demo/pde/nonlinear-poisson/python/demo.py            ?
> >> > > > >    demo/pde/poisson1D/python/demo.py                    viper
> >> > > > > problem with 1D demo/pde/waveguide/python/demo.py
> >> > > > >  results
> >> >
> >> > in
> >> >
> >> > > > > C++ and Python differ
> >> > > > >    demo/pde/dg/advection_diffusion/python/demo.py       ?
> >> > > >
> >> > > > This demo is somewhat depricated as it stands now. I added it
> >> > > > based on the previous c++ demo. Since then has the c++ demo
> >> > > > changed, to be more simple, but including the builtin OutflowFacet
> >> > > > special function. This is not included in the python interface.
> >> > > >
> >> > > > To get it up and running in python we need to add OutflowFacet to
> >> > > > the python interface. This should be doable, and quite
> >> > > > straightforward with the new function interface. Please correct
> >> > > > me:
> >> > > >
> >> > > > class OutflowFacet(ffc.Function,cpp.OutflowFacet):
> >> > > >     def __init__(self, vec_field):
> >> > > >         appropriate check on vec_field
> >> > > >         mesh = vec_field.function_space().mesh()
> >> > > >
> >> > > >         # Define the OutflowFacet form
> >> > > >         n = FacetNormal(mesh)
> >> > > >         a = ffc.dot(vec_field,n)*ffc.ds
> >> > > >         self._dolfin_form = Form(a)
> >> > > >
> >> > > >         domain  = dim2domain[mesh.topology().dim()]
> >> > > >         self._element = ffc.FiniteElement("Discontinuous
> >> > > > Lagrange", domain, 0)
> >> > > >
> >> > > >         ffc.Function.__init__(self, self._element)
> >> > > >         cpp.OutflowFacet(self, self._dolfin_form)
> >> > > >
> >> > > > It is a bastard wrt being a full fledged dolfin.Function, it does
> >> > > > not define its own function space. I do not know if this would be
> >> > > > a problem as the c++ counterpart neither initiate its base class
> >> > > > with a functionspace.
> >> > > >
> >> > > > Once this function is in place the rest should be quite straight
> >> >
> >> > forward.
> >> >
> >> > > > Johan
> >> > >
> >> > > It looks strange to me, and so does the C++ version (that a Function
> >> > > needs to be initialized with a form).
> >>
> >> That's what makes it a 'SpecialFunction' :)
> >>
> >> > > How about just evaluating the function at the midpoint of the facet
> >> > > and computing the inner product with the facet normal?
> >> >
> >> > Sounds resonable enough to me. I suppose an integral over the facet is
> >> > potentially more aqurate than just the midpoint evaluation.
> >>
> >> Yes, I guess this will be OK, and if it turns out that one needs the
> >> integral for accuracy reasons it is still possible to implement the
> >> function in the main.cpp file.
> >> We could do this for the CPP demo and use the 'new' OutflowFacet in the
> >> Python demo.
> >
> > If noone(tm) does not object to this difference in c++ vs python version
> > of the demo, I can update the python one, and take a try on the
> > OutflowFacet function in SpecialFunction to a not-so-special function.
> > This will then be instantiated using a FunctionSpace and the field
> > function.
> >
> > Johan
>
> Just a minor language nitpicking: The name "OutflowFacet" indicates that
> this is some sort of facet, i.e. a geometric entity, but it's a function,
> so... Maybe you mean "FacetOutflow"?

I don't know. It is a function that answers the question: 
  
  is the facet an outflow-facet

We could add "Is" in front to make it clearer?

Johan