On Mon, 20 Apr 2015 18:25:03 +0200 Jan Blechta <[email protected]> wrote:
> On Mon, 20 Apr 2015 16:00:52 +0000 > Anders Logg <[email protected]> wrote: > > > Yes, it might actually be that simple: The elements would be > > standard P1 elements with the only difference that the value of the > > basis functions are always one (each triangle has 3 basis function > > and each is = 1) and all derivatives are zero. > > This element does not make a sense with this definition. Imagine 2D > mesh of two triangles. There are 4 "basis" functions while the > dimension of the space is 2. In the other words, these "basis" > functions are not linearly independent hence they don't form a basis. In other words, span of suggested "basis" functions is exactly the usual space of piece-wise constants. That's why it is not used as a FE space. Rather as a transform for operator lumping. Jan > > Jan > > > > > Might be possible to "hack" by modifying > > _create_fiat_element(ufl_element) in ffc/fiatinterface.py. > > > > -- > > Anders > > > > > > mån 20 apr. 2015 kl 17:44 skrev Martin Sandve Alnæs > > <[email protected]>: > > > > > Doesn't sound that hard. Basically dofmaps like CG1 elements with > > > basis functions replaced by 1.0 on the entire support? > > > On 20 April 2015 at 15:37, Joakim Bø <[email protected]> wrote: > > > > > >> Thanks for answering! > > >> > > >> > > >> Anders got it right, discontinous and overlapping basis > > >> functions with the same global support as P1 tent functions. > > >> Sorry to hear that it would be hard to implement, but it came as > > >> no surprise... > > >> > > >> > > >> Thanks anyway! > > >> > > >> > > >> Joakim > > >> > > >> > > >> -- > > >> Joakim Bø > > >> Prosjektleder ENT3R UiO > > >> Tlf.: 915 24 326 > > >> > > >> http://www.ENT3R.no/OSLO > > >> ------------------------------ > > >> *From:* Anders Logg <[email protected]> > > >> *Sent:* 20 April 2015 13:46 > > >> *To:* Andrew McRae; Jan Blechta > > >> *Cc:* Joakim Bø; [email protected] > > >> *Subject:* Re: [FEniCS] Implement a new finite element type for > > >> testing purposes? > > >> > > >> If I understand correctly, you want discontinuous and > > >> overlapping basis functions with the same global support as the > > >> P1 tent functions. Unless you find a clever trick for how to > > >> treat this (perhaps via some linear algebra using P0 elements in > > >> combination with some suitable constraints), this looks > > >> difficult to implement in FEniCS. We assume each element is > > >> defined locally on triangles/tetrahedra. > > >> > > >> -- > > >> Anders > > >> > > >> > > >> mån 20 apr. 2015 kl 13:14 skrev Andrew McRae > > >> <[email protected]>: > > >> > > >>> I interpret it as a DG0, but where nodes are associated with > > >>> vertices. Related to mass-lumping, I guess. > > >>> > > >>> On 20 April 2015 at 12:07, Jan Blechta > > >>> <[email protected]> wrote: > > >>> > > >>>> On Fri, 17 Apr 2015 10:21:33 +0000 > > >>>> Joakim Bø <[email protected]> wrote: > > >>>> > > >>>> > Hi! > > >>>> > > > >>>> > > > >>>> > I am in need of a new type of basis function for testing > > >>>> > purposes. It is much similar to the basis functions of the > > >>>> > Taylor-Hood P1 element, the difference is that the functions > > >>>> > are piecewise constant equal to 1 in this "local > > >>>> > domain" (similar for 1D and 3D): > > >>>> > > > >>>> > > > >>>> > [http://www.fsz.bme.hu/~szirmay/radiosit/rad10.gif] > > >>>> > > > >>>> > > > >>>> > and zero in the rest of the domain. In general, phi_i = 1 for > > >>>> > "local domain of dof i", 0 else. > > >>>> > > >>>> If I understand your explanation correctly (it does not seem to > > >>>> match with the figure!), it is Discontinuous Lagrange element > > >>>> of degree 0, which is implemented. > > >>>> > > >>>> Jan > > >>>> > > >>>> > > > >>>> > > > >>>> > Would it be possible to implement this without too much work? > > >>>> > Or would it require a lot of effort? > > >>>> > > > >>>> > > > >>>> > Thanks! > > >>>> > > > >>>> > Joakim > > >>>> > > > >>>> > > > >>>> > -- > > >>>> > Joakim Bø > > >>>> > Prosjektleder ENT3R UiO > > >>>> > Tlf.: 915 24 326 > > >>>> > > > >>>> > http://www.ENT3R.no/OSLO > > >>>> > > >>>> _______________________________________________ > > >>>> fenics mailing list > > >>>> [email protected] > > >>>> http://fenicsproject.org/mailman/listinfo/fenics > > >>>> > > >>> > > >>> > > >> _______________________________________________ > > >> fenics mailing list > > >> [email protected] > > >> http://fenicsproject.org/mailman/listinfo/fenics > > >> > > >> > > _______________________________________________ > fenics mailing list > [email protected] > http://fenicsproject.org/mailman/listinfo/fenics _______________________________________________ fenics mailing list [email protected] http://fenicsproject.org/mailman/listinfo/fenics
