dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Thursday 30 October 2008 19:20:06 Anders Logg wrote:
> Most things are now in place, finally. At least we can run the Poisson
> demo again... :-)
>
> Anyway, take a look at demo/pde/poisson/main.cpp and see what you
> think. I think it looks pretty good, but please report if you have any
> ideas for further improvements of the interface while we're at it.

It looks nice, but I see some magic which I wish you can shed some light on. 

The introduction of PoissionFunctionSpace is not clear for me. Why do we have 
to instantiate the forms with it?

In the form file the two forms L and a are defined. These are then reflected 
in the main.cpp file as before. This is intuitive. But where does the 
PoissonFunctionSpace come from? I as a user has not defined it in the form 
file.

It might help if we introduce the notion of FunctionSpace in FFC/UFL. Then 
some of the magic would disapear I think.

The talk about a Function always knowing its Space was clear, you can always 
plot it, and so on. But then the introduction of the "magic" dedication of 
FunctionSpace broke that, and also made the actuall function of FunctionSpace 
more blurry.

Intuitively I would prefer:

  ...
  PoissonFunctionSpace V(mesh);

  Source f(V);
  Flux g(V);

  PoissonBilinearForm a();
  PoissonLinearForm L();

  L.set_f(f); L.set_g(g);
  ...

If this is not possible or if it is but we do not want it, please inform me.

> Any help with getting the remaining demos and the Python interface
> working again appreciated.

I could probably help with getting the python interface up and going, at least 
with the metaclass stuff discussed earlier. 


Johan