ufl team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

On 27 April 2011 17:07, Johan Hake <johan.hake@xxxxxxxxx> wrote:

> On Wednesday April 27 2011 07:54:14 Anders Logg wrote:
> > 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).
>
> Well, then I guess the form which get changed is already stripped from any
> DOLFIN specific objects :)
>

That could explain why it has worked. No side effects. Otherwise, just pure
luck...

Are there other situations where we per today change the form in a now
> illegal
> way? Adaptivity comes in my mind...
>

There probably are, since somebody experienced caching bugs related to this.

And I have to arrest you on the "now illegal", this is nothing new... :)

Martin


Johan
>
>
> > 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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