dolfin team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

On 27 April 2011 15:34, Anders Logg <logg@xxxxxxxxx> wrote:

> On Wed, Apr 27, 2011 at 03:24:05PM +0200, Martin Sandve Alnæs wrote:
> > On 27 April 2011 12:38, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
> >
> >
> >
> >     On 27/04/11 11:08, Kristian  lgaard wrote:
> >     > On 27 April 2011 11:52, Anders Logg <logg@xxxxxxxxx> wrote:
> >     >> On Wed, Apr 27, 2011 at 10:40:50AM +0100, Garth N. Wells wrote:
> >     >>> We need a quick discussion round to resolve this issue - DOLFIN
> is now
> >     >>> broken. I guess we need the form compiler to decide on the cell
> and
> >     >>> element type, and then have UFL return a new form.
> >     >>
> >     >> Yes, Martin mentioned at some point that it would be easy to add
> such
> >     >> a function to UFL (that takes a form and replacement elements and
> >     >> returns a new form).
> >     >>
> >     >> Martin, could you add such a function?
> >
> >
> > I started some time before easter, but as Garth says...
> >
> >
> >     > I think ufl.algorithm.transformations.replace would work if
> >     > FiniteElementBase derived from 'Terminal'.
> >     > Currently, it derives from 'object', what is the reason for that?
> >     > Anyway, it should be simple enough to add something equivalent for
> >     elements.
> >     >
> >
> >     I was thinking that we only need to replace Coefficients, e.g. if a
> >     Coefficient is defined using an 'incomplete element', FFC can create
> an
> >     element, a Coefficient and the perform the replacement. Looks like
> UFL
> >     can do this already.
> >
> >     The problem from the DOLFIN side is that the new UFL Coefficient will
> be
> >     different from the DOLFIN/UFL Coefficient, and would be a
> >     ufl.Coefficient and not a dolfin.Coefficient.
> >
> >
> > ... this may be a problem. Since I don't really know the motivation for
> this
> > feature request, I can't solve this problem for you.
>
> The motivation is that we want to accomplish what we now accomplish
> with the set_cell/degree functions that you have decided to remove.
>
> This allows us to write f = Expression("sin(x[0])") and let the form
> compiler choose a suitable approximation for the expression.
>

I'm fairly pessimistic... Let me look into it and come back later.

I spent quite a lot of time trying to get rid of (which failed) and
then minimize the requirement that an expr has a cell.
That problem may still work out ok for now, since
grad(Expression("sin(x[0]")) wouldn't work anyway.

Martin




> --
> Anders
>
>
>
>
>
> > Martin
> >
> >
> >
> >
> >     Garth
> >
> >     > Kristian
> >     >
> >     >>
> >     >>
> >     >>> Garth
> >     >>>
> >     >>> On 26/04/11 07:32, noreply@xxxxxxxxxxxxx wrote:
> >     >>>> ------------------------------------------------------------
> >     >>>> revno: 1014
> >     >>>> committer: Martin Aln s <martinal@xxxxxxxxx>
> >     >>>> branch nick: ufl
> >     >>>> timestamp: Fri 2011-04-15 21:44:37 +0200
> >     >>>> message:
> >     >>>>   Add warnings to set_foo functions in finiteelement.py,
> >     >>>>   and remove repr modifications after construction time.
> >     >>>>
> >     >>>>   If this will break your code, it likely wasn't working
> >     >>>>   correctly anyway and you need to rewrite it before you
> >     >>>>   can update to this UFL version.
> >     >>>>
> >     >>>>   The set_foo functions will be removed completely before UFL
> 1.0.
> >     >>>>
> >     >>>>   Happy easter holiday :)
> >     >>>> modified:
> >     >>>>   ufl/finiteelement.py
> >     >>>>
> >     >>>>
> >     >>>
> >     >>>
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> >     >>
> >     >> _______________________________________________
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> >
> >
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