dolfin team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting 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.

I think it's OK to illustrate two possible ways to go about the problem. The
results should be the same for this simple problem anyway, so it will still be
easy to make comparisons between the CPP and Python version.

> > > 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?

Sounds good to me.

Kristian
 
> Johan
>