Hi Stephen, I guess this is on me. Will look into this tomorrow and will get back to you. Thanks. -- Fabio 2015-10-06 19:36 GMT+01:00 Kramer, Stephan <s.kramer@imperial.ac.uk>:

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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