dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sun, Nov 02, 2008 at 04:28:45PM +0100, Johan Hake wrote:
> Hello!
> 
> I have fixed the swig interface so it compiles. I had to add SubFunction in 
> dolfin_function.h. If we do not want this we have to add 
> 
>   #include "SubFunction.h"
> 
> to Function.h, as it is in 0.8.1. 
> 
> As function inherits ufc::function I also %imported ufc.h and added ufc-1 as 
> swig dependencies in scons.cfg.
>
> I %renamed function.in to function._in and %extended the interface to 
> SubFunction so one can write 
> 
>   u in V
> 
> as discussed previously.

Very nice!

> I am curious of how we will fix the whole PyDOLFIN interface with the 
> precompiled function spaces aso. These can all be hidden in the assemble 
> function and/or in the LinearPDE class. But what if we want to expose a 
> FunctionSpace from a compiled form? Do we want this? 
> 
> Or what if we want to create a FunctionSpace from an element and a mesh. This 
> can be done more or less in the same way as we have solved Function in 0.8.1, 
> but then we miss the whole point of reusing FunctionSpaces.
> 
> Any good suggestions?
> 
> Johan

Here's a good suggestion... :-)

We create a new Python class (in site-packages/dolfin/functionspace.py)
which either inherits from FormCompiler.FiniteElement and
dolfin::FunctionSpace or owns such objects as member data.

In PyDOLFIN, FunctionSpace will then be something that replaces both
FormCompiler.FiniteElement and dolfin::FunctionSpace:

  V = FunctionSpace(mesh, "Lagrange", 1)
  v = TestFunction(V)
  u = TrialFunction(V)
  f = Function(V)
  a = dot(grad(v), grad(u))*dx
  L = v*f*dx
  A = assemble(a)
  b = assemble(L)

Note that the "triangle" or "tetrahedron" argument is not needed since
this can be deduced from the mesh.

I also suggest that we don't introduce the FunctionSpace concept in
the form compilers (FFC, SFC, UFL) since they should not know anything
about the mesh.

-- 
Anders

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