ufl team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Wed, Apr 27, 2011 at 03:48:42PM +0100, Garth N. Wells wrote:
>
>
> On 27/04/11 15:43, Johan Hake wrote:
> > When is the element/cell set for a coefficient?
>
> It's decided by the form compiler, which does the setting by calling the
> UFL set_foo functions.
>
> < If it is during code
> > generation we can add that process to preprocess or what ne it now has,
> > and the changes will only apply to the preprocessed form.

Good point. It's set in the analysis.py in FFC, right after the call
to preprocess (compute_form_data). It only relies on the

  form_data.cell
  form_data.sub_elements

So we might be able to handle it by making sure the preprocessed_form
gets as input the two arguments common_cell and common_degree that are
computed in the function _adjust_elements in analysis.py.

--
Anders



> > Johan
> >
> >
> > On Apr 27, 2011, at 7:00, Martin Sandve Alnæs <martinal@xxxxxxxxx
> > <mailto:martinal@xxxxxxxxx>> wrote:
> >
> >> On 27 April 2011 15:53, Kristian Ølgaard
> >> <<mailto:k.b.oelgaard@xxxxxxxxx>k.b.oelgaard@xxxxxxxxx
> >> <mailto:k.b.oelgaard@xxxxxxxxx>> wrote:
> >>
> >>     On 27 April 2011 15:27, Martin Sandve Alnæs
> >>     <<mailto:martinal@xxxxxxxxx>martinal@xxxxxxxxx
> >>     <mailto:martinal@xxxxxxxxx>> wrote:
> >>     > On 27 April 2011 13:38, Kristian Ølgaard
> >>     <<mailto:k.b.oelgaard@xxxxxxxxx>k.b.oelgaard@xxxxxxxxx
> >>     <mailto:k.b.oelgaard@xxxxxxxxx>> wrote:
> >>     >>
> >>     >> On 27 April 2011 13:03, Garth N. Wells
> >>     <<mailto:gnw20@xxxxxxxxx>gnw20@xxxxxxxxx <mailto:gnw20@xxxxxxxxx>>
> >>     wrote:
> >>     >> >
> >>     >> >
> >>     >> > On 27/04/11 12:00, Kristian Ølgaard wrote:
> >>     >> >> On 27 April 2011 12:38, Garth N. Wells
> >>     <<mailto:gnw20@xxxxxxxxx>gnw20@xxxxxxxxx <mailto:gnw20@xxxxxxxxx>>
> >>     wrote:
> >>     >> >>>
> >>     >> >>>
> >>     >> >>> On 27/04/11 11:08, Kristian Ølgaard wrote:
> >>     >> >>>> On 27 April 2011 11:52, Anders Logg
> >>     <<mailto:logg@xxxxxxxxx>logg@xxxxxxxxx <mailto: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 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.
> >>     >> >>
> >>     >> >> Yes, I think that should be possible. But what about quadrature
> >>     >> >> elements?
> >>     >> >>
> >>     >> >> If the scheme is not specified when constructing the element
> >>     (in the
> >>     >> >> form), then the scheme
> >>     >> >> will be determined by the commandline arguments (or
> >>     metadata) to FFC.
> >>     >> >> The
> >>     >> >> QuadratureElement needs the scheme information in the
> >>     constructor in
> >>     >> >> order to
> >>     >> >> generate the points for which it is defined.
> >>     >> >>
> >>     >> >
> >>     >> > I don't see the problem. Couldn't FFC generate a new
> >>     QuadratureElement
> >>     >> > (of the correct degree) and define a Coefficient on it?
> >>     >>
> >>     >> I guess it could.
> >>     >
> >>     > That would be natural to do simultaneously with replacing
> >>     elements in other
> >>     > coefficients.
> >>
> >>     Yes, we can start writing the code for this in ffc.analysis, but I
> >>     think that we will end up with something that might just as well
> >>     become a 'replace_element' function in ufl.algorithms.transformations
> >>
> >>
> >> The replace_elements algorithm will be easy to add to ufl,
> >> the problem is what to do with PyDOLFIN Functions and Expressions.
> >>
> >> Martin
> >>
> >>     >> Another question is if we should have a separate class in UFL for
> >>     >> quadrature elements?
> >>     >> The reason is that UFL uses (family, cell, degree) to check for
> >>     >> uniqueness (through __repr__ --> __hash__),
> >>     >> but the quadrature element will need the 'scheme' as well,
> >>     which can
> >>     >> be None until FFC determines it.
> >>     >
> >>     > Just set it to None by default.
> >>
> >>     Sure, since the scheme will be part of the __repr__, I'll add the
> >>     scheme argument between the degree and form_degree argument in
> >>     FiniteElement:
> >>
> >>     def __init__(self, family, cell, degree=None, quad_scheme=Nonw,
> >>     form_degree=None)
> >>
> >>     >>
> >>     >> Either we extend the __repr__ of FiniteElement to include the
> >>     scheme,
> >>     >
> >>     > No problem.
> >>
> >>     OK, that is my preferred solution. Just wanted to check if anyone had
> >>     a problem with the signature increase, or if there were some design
> >>     reasons to avoid this.
> >>
> >>     >>
> >>     >> or we can use a separate class QuadratureElement.
> >>     >
> >>     > That would require adding VectorQuadratureElement etc, and the
> >>     same in
> >>     > PyDolfin, major waste of time if you ask me.
> >>
> >>     Yes I agree, but necessary if someone objects to extending __repr__.
> >>
> >>     Kristian
> >>
> >>     > Martin
> >>     >>
> >>     >> For the majority of finite elements the 'scheme' information in
> >>     >> __repr__ is superfluous, so a separate class might be preferable.
> >>     >> If we use a separate class, then the question is if we want to do:
> >>     >>
> >>     >> 1) element = QuadratureElement(cell, degree, scheme)
> >>     >> or
> >>     >> 2) element = FiniteElement(family, cell, degree, scheme=scheme)
> >>     >>
> >>     >> when creating a quadrature element object.
> >>     >>
> >>     >> For case 2 we probably need to implement FiniteElement.__new__ to
> >>     >> return a QuadratureElement if family == 'Quadrature'.
> >>     >>
> >>     >> Kristian
> >>     >>
> >>     >> > Garth
> >>     >> >
> >>     >> >> Kristian
> >>     >> >>
> >>     >> >>> 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.
> >>     >> >>>
> >>     >> >>> Garth
> >>     >> >>>
> >>     >> >>>> Kristian
> >>     >> >>>>
> >>     >> >>>>>
> >>     >> >>>>>
> >>     >> >>>>>> Garth
> >>     >> >>>>>>
> >>     >> >>>>>> On 26/04/11 07:32,
> >>     <mailto:noreply@xxxxxxxxxxxxx>noreply@xxxxxxxxxxxxx
> >>     <mailto:noreply@xxxxxxxxxxxxx> wrote:
> >>     >> >>>>>>>
> >>     ------------------------------------------------------------
> >>     >> >>>>>>> revno: 1014
> >>     >> >>>>>>> committer: Martin Alnæs
> >>     <<mailto:martinal@xxxxxxxxx>martinal@xxxxxxxxx
> >>     <mailto: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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