ufl team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Mar 30, 2009 at 02:15:25AM +0200, UFL wrote:
> One or more new changesets pushed to the primary ufl repository.
> A short summary of the last three changesets is included below.
> 
> changeset:   778:540ea93daca99a3893f2a1417d1c97eeea2e9479
> tag:         tip
> user:        Anders Logg <logg@xxxxxxxxx>
> date:        Mon Mar 30 02:14:58 2009 +0200
> files:       ufl/form.py
> description:
> Implement short-hand inner product notation (v, u)

Just arrived in LA and wanted to push something I played with on the
plane.

I've modified form.py to allow a Form to be initialized from a tuple
of integrands and optional measures. It's a small fix, just an added
function call in the constructor that extracts the proper
integrals. Note that no operator overloading is used to accomplish
this. The expression is just written as a common Python tuple from
which the UFL Form is extracted.

The new notation (which is optional) allows the use of the inner
product notation commonly used in the formulation of most finite
element methods.

Here are some examples:

Poisson:

  a = (grad(v), grad(u))

Convection-diffusion-reaction:

  a = (v, dot(beta, grad(u))) + (grad(v), grad(u)) + (v, u)

DG Poisson:

  a = (grad(v), grad(u))
    + (alpha/h('+')*jump(v, n), jump(u, n), dS)
    + (gamma/h*v, u, ds)
    ...

A term is specified either as a tuple

  (expr1, expr2)

or as a triple

  (expr1, expr2, measure)

If no measure is specified, then dx is used.

Caveats:

1. Subtraction does not work, so one needs to do

  a = (grad(v), grad(u)) + (-v, u)

2. Mixing notation does not work:

  a = (grad(v), grad(u)) + v*u*dx

Does this seem ok? I think it's pretty cool. :-)

-- 
Anders

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