dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Jun 10, 2008 at 05:08:57PM +0200, Martin Sandve Alnæs wrote:
> 2008/6/10 Anders Logg <logg@xxxxxxxxx>:
> > On Tue, Jun 10, 2008 at 04:41:25PM +0200, Martin Sandve Alnæs wrote:
> >> Maybe this design works?
> >>
> >> x is coordinates, c is cell info
> >>
> >> class Function
> >> {
> >>   virtual void eval(v, x, c) { eval(v, x); }
> >>   virtual void eval(v, x) { dolfin_error("Missing implementation of eval."); }
> >> };
> >>
> >> class A: Function
> >> {
> >>   void eval(v, x) { do_my_thing; }
> >> };
> >>
> >> class B: Function
> >> {
> >>   void eval(v, x, c) { do_my_thing; }
> >> };
> >>
> >> The assembler always call eval(v,x,c), the user overloads the one
> >> he wants. There are already lots of redirecting back and forth in
> >> the Function hierarchy, so the overhead shouldn't become larger.
> >> If a user-function that depends on cell info is called in a context
> >> without cell info, i.e. eval(v,x) is called, this triggers an error.
> >>
> >> Inheritance in Python is probably a problem here (SWIG issues).
> >> Alternatively, name them eval(v,x) and eval_cell(v,x,c) or something
> >> to solve that problem.
> >
> > Good, but it becomes a bit messy if we also want to include the other
> > hidden arguments (see protected section of Function):
> >
> >  /// Access current facet normal (available during assembly for user-defined function)
> >  Point normal() const;
> >
> >  /// Access current facet (available during assembly for user-defined functions)
> >  int facet() const;
> 
> We could pack all geometry data in one argument.
> Or have a separate eval_facet which takes these arguments.

I think we should have eval_facet. But how do we pack geometry in one
argument in C++? We might want the cell, the subdomain, the current
time, and possibly other things.

-- 
Anders

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