More weirdness, I'm afraid. If I change the function space V to:

   V = FunctionSpace(mesh2d, "RT", 1)

I still get different answers between M and M1+M2. This is using the
bendy branches for firedrake/ffc/ufl and
enhance-rewriter-mode3-logflops for COFFEE. Again M==M1+M2 using
parameters['coffee']={} and I get the same answer for M in "flat" firedrake.

Any other magic branches I could try? ;-)
Seriously though, any suggestions are welcome

Cheers
Stephan


On 02/10/15 13:10, Stephan Kramer 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
>
> I really expect M, M1+M2 and M0 to be all the same. On firedrake master
> (and in fact Dolfin) these are all the same indeed. But in my fd_bendy
> enviroment (fd_bendy for ffc and ufl, bendy_changes for firedrake) the
> values for M are different. Final piece of information is that if I use
> parameters['coffee']={}, everything is fine again. Other than that I'm
> stuck though, so I'd much appreciate any pointers into what I could
> check next
>
> Cheers
> Stephan

>
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>
>


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