ufl team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2008/9/4 Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>:
>
>
> Hi,
>
> I think we've addressed this before, but I'm not sure when and what the outcome
> was. The following 3 forms all result in the same code apart from some variable
> names:
>
> element = FiniteElement("Lagrange", "triangle", 1)
>
> v = TestFunction(element)
> u = TrialFunction(element)
> f = Function(element)
>
> c = Constant("triangle")
>
> a = c*dot(grad(v), grad(u))*dx          # 0
> a = dot(grad(v), mult(c, grad(u)))*dx   # 1
> a = dot(grad(v), grad(c*u))*dx          # 2
>
> The first two forms are basically identical. However, the latter results in 2
> monomial terms that FFC must consider. This is obviously a waste of time since
> one evaluates to zero anyway. Should analyze.py or something else pick this up?
> How will this be dealt with in UFL? Or should it be handled in the compilers?
>
> Kristian

I believe I will implement automatic differentiation as algorithms
working directly on UFL.
I'll have to get back to the details later (hopefully I'll have
something working before the
end of the month).

--
Martin