dolfin team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

On Fri, Mar 13, 2009 at 10:11 AM, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>
>
> Martin Sandve Alnæs wrote:
>>
>> On Thu, Mar 12, 2009 at 11:05 PM, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>>>
>>> Anders Logg wrote:
>>>> It seems it wouldn't be anymore difficult than what we have now. For
>>>> example, the Poisson demo would be
>>>>
>>>>  UnitSquare mesh(32, 32);
>>>>  PoissonFunctionSpace V(mesh);
>>>>
>>>>  PoissonBilinearForm a(V, V);
>>>>  PoissonLinearForm L(V);
>>>>  Source f(V);
>>>>  L.f = f; // without side effect
>>>>
>>> That's OK, but if you have >5 coefficients with >5 different functions
>>> spaces, it's not nice.
>>
>> This feature will without doubt lead to many users writing code where
>> function spaces are duplicated. If you have a form where more than one
>> coefficient shares same function space, you shouldn't use this feature.
>> Even if it is well documented, people don't generally read documentation
>> until things break.
>>
>> If we strictly require that functions have function spaces, we can instead
>> check that the form coefficient function spaces match the given function
>> in "L.f = f;". Then your problem is reduced to runtime "typechecking".
>>
>
> The problem is the number of lines a user must program, and having
> intelligible names for the spaces.

The Form/FunctionSpace code generation in wrote and placed
in dolfin_utils/ produces names like this from .ufl files:

    PoissonBilinearForm::TrialSpace V(mesh);
    PoissonLinearForm::CoefficientSpace_f F(mesh);
    PoissonLinearForm::CoefficientSpace_g G(mesh);

    PoissonBilinearForm a(V, V);
    PoissonLinearForm L(V);

And after working a bit with this I wrote the following:

// Suggestions for improvement to naming conventions:
//  Poisson::BilinearForm::TrialSpace V(mesh);
//  Poisson::BilinearForm::CoefficientSpace_f F(mesh);
//  Poisson::CoefficientSpace_f F(mesh);
//  Poisson::CoefficientSpace_g G(mesh);
//
//  Poisson::BilinearForm a(V, V);
//  Poisson::LinearForm L(V);

Here "Poisson" is the prefix taken from "Poisson.ufl",
PoissonBilinearForm is a typedef to PoissonForm_a
such that any number of forms can be defined in each file,
and "g" in PoissonLinearForm::CoefficientSpace_g is
the name of the variable holding the Function in the .ufl file
(g = Function(...)).

I find this acceptable to work with.

Martin