dolfin team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxx>]

On Mon, 2006-02-13 at 10:53 -0600, Anders Logg wrote:

> ok, let's begin with fixing the XML input/output for Vector. 

Sounds good.


> Then we
> should have what we need to read/write functions + we also need to
> decide on which elements to precompile and store.
> 
> The XML format for Vector is temporarily disabled after the change of
> linear algebra backend to PETSc, so it should be easy to fix.
> 
> There's a lot of different elements we would potentially need to
> pregenerate, including different degree polynomials, vector-valued
> elements with different number of components, mixed elements etc, so
> it's not obvious which we should pick. (Of course if something is
> missing in the first set of elements we can always add it later when
> someone needs it.)

I would consider leaving this up to the user because of the huge number
of elements that this could lead to.

>  
> > 
> > > > > 2. An interface for projecting/interpolating between Functions. The
> > > > > main example which requires some manual work in solvers is defining
> > > > > the initial values by a UserFunction and wanting to represent that as
> > > > > a DiscreteFunction.
> > > > 
> > > > I'm not sure what you mean. I thought I solved this with the new
> > > > functionality I added to the Function class last week. You can define
> > > > a Function for the initial value by overloading eval(), or even by
> > > > 
> > > > Function u = 0.0;
> > > > 
> > > > and then u can change from being a user-defined Function to a discrete
> > > > Function. See new convection-diffusion demo.
> > > > 
> > > > You can also do
> > > > 
> > > > Function u(x, mesh, element);
> > > > u = f;
> > > > 
> > > > to interpolate f to u.
> > > > 
> > > 
> > Is the interpolation linear (to the vertexes only), or does it work for
> > higher-order elements?
> 
> Works for all types of elements. The function f is evaluated at all
> nodes of the element that defines u.
> 
Great!

Garth

> /Anders
> 
> > Garth
> > 
> > > Ok, great! I'm sorry, I didn't realize this was what you added last
> > > week.
> > > 
> > > I think interpolation is enough, projection can wait.
> > > 
> > > > I have limited time to work on new features before Geilo, but I can
> > > > probably fit something in if I get some help.
> > > > 
> > > 
> > > Yes, I also have limited time. But maybe we can at least start looking
> > > at Function input and decide what we should do, i.e. if we should
> > > design a DOLFIN XML data format for Functions or use the VTK format.
> > > 
> > >   Johan
> > > 
> > > _______________________________________________
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> > > DOLFIN-dev@xxxxxxxxxx
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> 
> -- 
> Anders Logg
> Research Assistant Professor
> Toyota Technological Institute at Chicago
> http://www.tti-c.org/logg/
> 
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