dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

I'm not sure we need such classes/objects. Wouldn't it be enough to add a new function to the element class to return a string like "L2", "H1" etc?

UFC is up for extension in the near future so this should be added as a UFC blueprint.

--
Anders

11 sep 2012 kl. 21:07 skrev David Ham <David.Ham@xxxxxxxxxxxxxx>:

> FWIW I agree with Martin that the element class needs to be able to
> report this. For instance, if someone were to add non-equispaced
> Lagrange polynomials which are typically used for higher order
> computations, these need to show up as continuous, which would not
> safely happen if you just check the element family.
> 
> A suggestion, if I may, which seems sort of mathematically nice to me
> would be to define a SobolevSpace class. Instances of that class would
> be comparable with each other and with element objects so one could
> inquire whether an element has continuity in a given sense.
> 
> For instance there might be SobolevSpace objects H1, H1_div, H1_curl,
> L_2. These would compare H1>H1_div>L_2,  H1>H1_curl>L_2.
> 
> A DG element object d would compare d<L_2 but false for any other inclusion
> A CG element would compare true for all the spaces.
> RT1 would compare true for H1_div and L2 but not for H1_curl or H1 and so on.
> 
> Thought would need to be given to whether it is necessary to enforce
> dimension matching properly or not.
> 
> In the Python level it might be more natural to make the inclusion
> operator "in" rather than <.
> 
> Regards,
> 
> David
> 
> 
> 
> On 11 September 2012 18:20, Martin Sandve Alnæs <martinal@xxxxxxxxx> wrote:
>> This is maybe cumbersome, but you can identify DG elements by checking
>> the number of dofs per mesh entity through ufc::dof_map, with the function
>>    /// Return the number of dofs associated with each cell entity of
>> dimension d
>>    virtual unsigned int num_entity_dofs(unsigned int d) const = 0;
>> if
>>  dm->num_entity_dofs(0) == dm->max_local_dimension()
>> then no dofs are shared between elements.
>> 
>> However this does not cover elements where dofs are shared but
>> the functions are still discontinuous in certain senses.
>> I guess more information will be needed in the ufc element classes.
>> 
>> Martin
>> 
>> 
>> On 11 September 2012 16:13, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>>> On Tue, Sep 11, 2012 at 11:36 AM, Joachim Berdal Haga <jobh@xxxxxxxxx> wrote:
>>>> Ok! I'll just check the element family then. Is there a more robust
>>>> way to query it (in C++) than parsing
>>>> f->function_space()->element()->signature()?
>>>> 
>>> 
>>> The signature should not be used. It's not robust. Using the signature
>>> has caused problems in the past.
>>> 
>>> Garth
>>> 
>>>> -j.
>>>> 
>>>> On 11 September 2012 12:09, Kent-Andre Mardal <kent-and@xxxxxxxxx> wrote:
>>>>> I guess it is only the Lagrange/CG element that is continuous. The others
>>>>> are only continuous
>>>>> in certain senses or directions. I don't think there is any meta data that
>>>>> contains this
>>>>> info.
>>>>> 
>>>>> Kent
>>>>> 
>>>>> On 11 September 2012 11:56, Joachim Berdal Haga <jobh@xxxxxxxxx> wrote:
>>>>>> 
>>>>>> Is there a simple way to find out whether an arbitrary Function (or
>>>>>> FunctionSpace) is continuous across cells in C++?
>>>>>> 
>>>>>> -j.
>>>>>> 
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>>>>> 
>>>> 
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> 
> 
> -- 
> Dr David Ham
> Department of Computing
> Imperial College London
> 
> http://www.imperial.ac.uk/people/david.ham
> 
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