dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Apr 27, 2011 at 09:30:08PM +0200, Martin Sandve Alnæs wrote:
> 2011/4/27 Johan Hake <johan.hake@xxxxxxxxx>
>
>     On Wednesday April 27 2011 12:03:56 Martin Sandve Aln s wrote:
>     > On 27 April 2011 19:07, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>     > > I'm starting here a new thread on how to deal with the recent change in
>     > > UFL that has broken a good number of DOLFIN demos. The previous thread
>     > > meandered and got side-tracked.
>     > >
>     > > The framework in we need to operate is:
>     > >
>     > > A. UFL will not allow forms to be modified post-construction.
>     > >
>     > > B. It should be relatively easy to replace ufl.Coefficients in a form
>     > > and return a new form.
>     > >
>     > > C. The issue with replacing ufl.Coefficients is that we lose DOLFIN
>     data
>     > > (like the eval() functions) associated with the removed coefficients.
>     > >
>     > >
>     > > I'll kick off with the obvious solution:
>     > >
>     > > 1. Require that all DOLFIN Expressions are associated with a
>     > > ufl.FiniteElement.
>     > >
>     > > Other solutions?
>     > >
>     > > Garth
>     >
>     > 2.  At the stage when ffc calls ufl.preprocess, or even in
>     ufl.preprocess,
>     > let the preprocessed form contain ufl Coefficients with new elements in
>     > place of the dolfin.Expressions. This is similar to the replacements done
>     > for renumbering of Coefficients, and could either be done simultaneously
>     or
>     > as an additional step. The original Form and Expression objects will be
>     > untouched, and the preprocessed form will be fine.
>
>     +
>
>     However, setting cell and degree is done during analysis and relies on
>     form_data. The form is also preprocessed when the form_data is extracted.
>     This
>     means that for the preprocessed form to get correct signature, cell and
>     degrees being set, we need to break up the logic.
>
>      1) extract form_data
>      2) set degree and cell
>      3) genererate preprocessed form
>
>
> Lets figure out the exact algorithm if we need it. It could perhaps be
> integrated better with preprocess. Or it might be better to extract just the
> information needed to determine degree and cell first, and pass the element
> replacements to preprocess.

That's what I suggested in an earlier mail. Preprocess already gets
common_cell. We could also figure out common_degree before calling
preprocess but that requires getting the data stored in
form_data.sub_elements.

--
Anders