Comment 6 for bug 862383

Would it be an idea to also add 'FacetArea' as a GeometricQuantity to
Cell in UFL?
Then h_F in the bug report can be defined as:

h_F = cell.facet_area

i.e., the area of the facet currently being integrated.

One could perhaps also consider defining SurfaceArea, the sum of all
FacetAreas of a Cell.

Note that:

M = h_F*dx

should be illegal, but this can be checked in UFL at compile time.

Kristian

On 17 November 2011 01:24, Anders Logg <email address hidden> wrote:
> ** Changed in: dolfin
>       Status: In Progress => Fix Committed
>
> --
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> https://bugs.launchpad.net/bugs/862383
>
> Title:
>  FacetArea evaluation fails if the form includes both a cell integral
>  and an interior facet integral
>
> Status in DOLFIN:
>  Fix Committed
>
> Bug description:
>  Reproduce with this script:
>
>  from dolfin import *
>
>  mesh = UnitSquare(3,3)
>  V = VectorFunctionSpace(mesh, "DG", 1)
>  v = TestFunction(V)
>  u = TrialFunction(V)
>
>  h_F = FacetArea(mesh)('+')
>
>  # Ok:
>  a1 = h_F*dot(jump(u),jump(v))*dS
>  A1 = assemble(a1)
>
>  # Fails:
>  a2 = a1 + inner(grad(u), grad(v))*dx
>  A2 = assemble(a2)
>
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