dolfin team mailing list archive

[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).
>
> 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. 


Johan