[firedrake] difference between matrix-action and form-action

Dear firedrakers, Assume I have assembled a UFL form in the HDiv space: form_uu = [a UFL form] mat_uu = assemble(form_uu,bcs=bcs) then shouldn’t the following two experssions fo exactly the same thing? version A: with v.dat.vec as y: with u.dat.vec_ro as x: mat_uu.M.handle.mult(x,y) version B: v = self._mutilde._form_action(u) as fas as I can tell, only version B gives the correct result in my case. Thanks, Eike