dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

The problem is the Functions AvgMeshSize and FacetNormal. Right now, 
they are wrapped dolfin::Function(s) (C++). They also need to be 
ffc.Function(s).

The idea is: a Function in PyDOLFIN should be both a DOLFIN Function (so 
it can be plotted, saved to file, have values etc) and a FFC Function 
(so it can be used in expressions).

This can be fixed by adding renames cpp_AvgMeshSize and cpp_FacetNormal 
in dolfin_function_pre.i, renaming the corresponding FFC functions in 
assembly.py, and then finally adding new classes in assembly.py that 
inherit from both.

The idea is: rename both the DOLFIN and FFC functions and then create 
something new that inherits from both.

I can take a look when I get the chance, but feel free to try it out.

/Anders


Kristian Oelgaard wrote:
> Hi,
>
> I have some problems using the Python interface to DOLFIN.
>
> The two following form will not compile
>
> element = FiniteElement("Discontinuous Lagrange", "triangle", 1)
> mesh = UnitSquare(2,2)
> v = TestFunction(element)
> u = TrialFunction(element)
>
> h = AvgMeshSize(mesh)
> n = FacetNormal(mesh)
>
> a = 1.0/h*dot(v('+'),u('-'))*dS
>
> error:
> Traceback (most recent call last):
>   File "demo.py", line 70, in <module>
>     a0 = 1.0/h*dot(v('+'),u('-'))*dS
> TypeError: unsupported operand type(s) for /: 'float' and 'AvgMeshSize'
>
> and
> a = dot(jump(v,n),jump(u,n))*dS
>
> error:
> Traceback (most recent call last):
>   File "demo.py", line 71, in <module>
>     a1 = dot(jump(v,n),jump(u,n))*dS
>   File "/home/oelgaard/fenics/ffc/src/ffc/compiler/language/operators.py", line
> 228, in jump
>     raise FormError, ((v, n), "Jump operator with respect to normal vector does
> not support tensors of this rank.")
> ffc.common.exceptions.FormError
>
> Should I use the interface differently?
>
> Kristian
>
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