'SIMD: don't know how I shall evaluate in Assemble BilinearForm' error

I used the solution of a problem to be an input of another problem.

When I tried with an exact solution (a CoefficientFunction), the code worked well.

When I tried with an computed solution (a GridFunctioN), there is an error as follows.

The error was disappeared when I deleted line 248 (But I need this line in the discrete formulation.):

So I guess the error maybe come from u.

Please see the attached file for details.

Can I convert a gridfunction to a similar form of a coefficient function? Could you please tell me how to fix that error?
Thank you so much.

Hi dong,

u is a VectorL2 GridFunction, which you want to evaluate at the boundary.
L2 (and therefore VectorL2) has no well defined Trace (the L2 space returns a "DummyFE" which seems to cause an exception).

Further, in the definition of the space the dirichlet flag will be ignored (the number of dofs and number of free dofs coincide).

Best
Michael