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

[Eike Mueller]

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