dolfin team mailing list archive

[Murtazo Nazarov <murtazo@xxxxxxxxxx>]

Murtazo Nazarov wrote:
> Question #103034 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/103034
>
> Murtazo Nazarov posted a new comment:
> Anders Logg wrote:
>   
> > Your question #103034 on DOLFIN changed:
> > https://answers.launchpad.net/dolfin/+question/103034
> >
> > Anders Logg posted a new comment:
> > On Mon, Mar 15, 2010 at 03:45:30PM -0000, Murtazo Nazarov wrote:
> >   
> >     
> > > Question #103034 on DOLFIN changed:
> > > https://answers.launchpad.net/dolfin/+question/103034
> > >
> > > Murtazo Nazarov posted a new comment:
> > > Anders Logg wrote:
> > >     
> > >       
> > > > Your question #103034 on DOLFIN changed:
> > > > https://answers.launchpad.net/dolfin/+question/103034
> > > >
> > > > Anders Logg posted a new comment:
> > > > On Sun, Mar 14, 2010 at 11:48:21PM -0000, Murtazo Nazarov wrote:
> > > >
> > > >       
> > > >         
> > > > > Question #103034 on DOLFIN changed:
> > > > > https://answers.launchpad.net/dolfin/+question/103034
> > > > >
> > > > > Murtazo Nazarov posted a new comment:
> > > > > Murtazo Nazarov wrote:
> > > > >
> > > > >         
> > > > >           
> > > > > > Your question #103034 on DOLFIN changed:
> > > > > > https://answers.launchpad.net/dolfin/+question/103034
> > > > > >
> > > > > >     Status: Answered => Open
> > > > > >
> > > > > > You are still having a problem:
> > > > > > Anders Logg wrote:
> > > > > >
> > > > > >
> > > > > >           
> > > > > >             
> > > > > > > Question #103034 on DOLFIN changed:
> > > > > > > https://answers.launchpad.net/dolfin/+question/103034
> > > > > > >
> > > > > > >     Status: Open => Answered
> > > > > > >
> > > > > > > Anders Logg proposed the following answer:
> > > > > > > On Wed, Mar 03, 2010 at 02:36:59AM -0000, Murtazo Nazarov wrote:
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >             
> > > > > > >               
> > > > > > > > New question #103034 on DOLFIN:
> > > > > > > > https://answers.launchpad.net/dolfin/+question/103034
> > > > > > > >
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > I am wondering how to compute an L1-norm, and L_inf norm of a functional on the cell. For instance how to compute
> > > > > > > >
> > > > > > > > 1. ||\div(Pu)||_{L_\infty} ?
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >               
> > > > > > > >                 
> > > > > > > Try projecting div(Pu) onto piecewise constants and then pick the
> > > > > > > largest absolute value in the vector.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >             
> > > > > > >               
> > > > > > I need L_inf norm on the cell. With this way, doesn't give the L_inf for
> > > > > > the entire domain?
> > > > > >
> > > > > > murtazo
> > > > > >
> > > > > >
> > > > > >
> > > > > >           
> > > > > >             
> > > > > Instead of projecting div(Pu) onto piecewise constants, I projected it
> > > > > into dG(1), with this way I get three values on each cell, which I can
> > > > > then pick up the largest of them. That gives me then L_inf_K, where K is
> > > > > a cell. Now, I cannot figured out how is the numbering done for the
> > > > > dG(1) elements.
> > > > >
> > > > > If N is a total number of cells, then my projected vector Pdg has 3*N
> > > > > elements. How can I pick up elements of Pdg in the cell K?
> > > > >
> > > > > Thanks,
> > > > > murtazo
> > > > >
> > > > >         
> > > > >           
> > > > Why do you use DG(1) instead of DG(0)? If you use DG(0), the numbering
> > > > is easier.
> > > >
> > > >
> > > >       
> > > >         
> > > DG(0) gives me an average of the function I have on the cell, however
> > > the values can be large on the vertices especially in the places where
> > > shocks exist.
> > >
> > > murtazo
> > >     
> > >       
> > ok, then I suggest working through tabulate_dofs in the DofMap class
> > to get the degrees of freedom for any given cell. Then you can just
> > access those from the vector.
> >
> > --
> > Anders
> >
> >   
> >     
>
> I have some problem with dofmap for dG(1) elements. Here the piece of 
> the code I am using:
>
>       const DofMap& dofmap = U.function_space().dofmap();
>       real Umax = 0.;
>       UFCCell ufc_cell(*cell);
>       uint dofsize = dofmap.max_local_dimension();
>       uint* cell_dofs = new uint[dofsize];
>       dofmap.tabulate_dofs(cell_dofs, ufc_cell, cid);
>       for (int i = 0; i < dofsize; i++){
>         Umax = max(Umax, fabs(Uarr[cell_dofs[i]]));
>       }
>
> It works fine for dG(0), however it gives strange results for dG(1).
>
> Can anyone help?
>
> Thanks,
> Murtazo
>
>   

it seems it works now.

murtazo

>   
> >   
> >     
> > > >       
> > > >         
> > > > > > > > 2. ||\div(Pu)||_{L_1} ?
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >               
> > > > > > > >                 
> > > > > > > Try
> > > > > > >
> > > > > > > M = abs(div(Pu))*dx
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >             
> > > > > > >               
> > > > > > > > where u is velocity (vector) and P is pressure (scalar). L2 norm is obvious to do.
> > > > > > > >
> > > > > > > > I use C++ interface
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >               
> > > > > > > >                 
> > > >       
> > > >         
> >     
>
>