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. 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
