ffc team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting 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.

So, working directly on UFL inside UFL, or is it in FFC working on output from
UFL. What I mean is, will FFC (or any other form compiler) only 'see' the
non-zero terms?

> I'll have to get back to the details later (hopefully I'll have
> something working before the
> end of the month).

Great.

Kristian
 
> --
> Martin
>