> On 2 Oct 2015, at 13:10, Stephan Kramer <s.kramer@imperial.ac.uk> wrote:
>
> Hey guys
>
> I've been trying to implement a simple IP viscosity scheme for DG, but was getting weird results, which I think I've tracked down to a bug related to fd_bendy.
>
> If I run the following:
>
> from firedrake import *
>
> mesh2d = UnitSquareMesh(1,1)
> V = VectorFunctionSpace(mesh2d, "DG", 1)
> uv = Function(V)
> U_test = TestFunction(V)
>
> n = FacetNormal(mesh2d)
> F1 = dot(jump(U_test[0], n), jump(uv[0], n))*dS
> F2 = -dot(avg(grad(U_test[0])), jump(uv[0], n))*dS
> F=F1+F2
> F0 = dot(jump(U_test[0],n)-avg(grad(U_test[0])), jump(uv[0], n))*dS
>
> M=assemble(derivative(F, uv)).M.values
> M1=assemble(derivative(F1, uv)).M.values
> M2=assemble(derivative(F2, uv)).M.values
> M0=assemble(derivative(F0, uv)).M.values

Do you mind wrapping this up as a test (to merge against current master) that ensures we don't regress when merging bendy?

Lawrence