ffc team mailing list archive

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

On 29 January 2010 01:23, Anders Logg <logg@xxxxxxxxx> wrote:
> There seem to be just a couple of issues remaining in order of importance:
>
> 1. QuadratureElement
>
> 2. DOLFIN fem unit test
>
> 3. evaluate_basis_derivatives
>
> 4. RestrictedElement
>
> Among these, I would say 1-2 are crucial to fix before 0.9.0,
> but 3-4 are less crucial.
>
> It would be good to have evaluate_basis_derivatives working, but I
> don't know how much work is involved.

First my apologies for the late reply, Internet was down again all morning and it pisses me off.

Now that BDM elements also compiles for gcc it looks like everything is in place for evaluate_basis.
CG and CR elements work, and so does all linear elements and DG constants. 2nd and 3rd order elements of BDM, RT, and DG type does not give the same result but there are explanations for this and at least it looks like they agree with the values you would get from FIAT if you tabulate on the reference element.

evaluate_basis_derivatives works for CG elements and for most elements of degree 1.

I'm working on some kind of unit testing framework for evaluate_basis and evaluate_basis_derivatives, such that we can make sure that at least cpp code and FIAT agrees on the reference element. If this test works, then the only bug can be in the transformation back to the physical element, but since this works for CG elements I don't see why it shouldn't for other elements too.
However, I'll put this development on hold until Quadrature and Restricted elements work.

> RestrictedElement is also good to have, but I would say it is less
> important, especially since it's unclear what exactly it should do and
> how it should be implemented.

It should be implemented like I did it in the old FFC :)
w.r.t. the demo, it should test if restrictions on a MixedElement are propagated to the sub elements and that a restricted element can appear in a MixedElement.

> We should also have the following in mind:
>
> (i) The number of users relying on restricted elements is most likely
> very small and they are very likely using the development version
> anyway so if a fix for restricted elements comes next week, that will
> be ok.
>
> (ii) If we make a release of 0.9.0 now and package it for Debian/Ubuntu,
> it is still possible to request Ubuntu to pull bug fixes for some
> time. So we can release 0.9.0 now and then 0.9.1 in a couple of weeks.

I think this sounds like a good plan. I'll work on getting QuadratureElement up and running and the RestrictedElement.
If there are any bugs in evaluate_basis_derivatives we'll release it in 0.9.1.
The code really needs some cleaning up, and we should also rearrange some of the utility functions, but that can wait until 0.9.1.

Kristian

> One of the reasons I'm pressing on with the release is the interface
> changes that we have made in both FFC and DOLFIN. It would be good to
> introduce these as early as possible to avoid confusion about how to
> write a form file (Coefficient, not Function) and how to implement
> Expressions (Array, not std::vector).
>
> --
> Anders
>
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