ufl team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Feb 23, 2009 at 04:52:32PM +0100, Martin Sandve Alnæs wrote:
> On Mon, Feb 23, 2009 at 2:10 PM, Anders Logg <logg@xxxxxxxxx> wrote:
> > On Mon, Feb 23, 2009 at 02:05:00PM +0100, Martin Sandve Alnæs wrote:
> >> On Mon, Feb 23, 2009 at 12:36 PM, Anders Logg <logg@xxxxxxxxx> wrote:
> >> > On Mon, Feb 23, 2009 at 11:51:42AM +0100, Martin Sandve Alnæs wrote:
> >> >> Looks ok, but I simplified it further.
> >> >
> >> > Looks nice and simple.
> >> >
> >> >> Note that we might need a more sofisticated renumbering
> >> >> later, to discover that e.g. u[i]*v[i] and u[j]*v[j] are the
> >> >> same expression, for fast optimization of quadrature code.
> >> >
> >> > ok
> >> >
> >> >> Also, I moved the argument renumbering to FormData,
> >> >> take a look at it. I've removed the "classes" and
> >> >> "*_renumbering" members of FormData. We should
> >> >> go through the FormData structure soon to finalize
> >> >> it as well as we can.
> >> >
> >> > I wasn't aware that FormData already did some renumbering. What does
> >> > it renumber and how does it relate to renumber_indices?
> >>
> >> It didn't renumber anything, what I removed was a numbering mapping,
> >> mapping each function to its place in the form in [0,n).
> >> But now it renumbers the form arguments (not the indices).
> >> It has to apply expand_derivatives before this, since
> >> this can result in changes in the argument list.
> >> (I don't really like this, see the FIXME comment in formdata.py).
> >> The current implementation of expand_derivatives calls expand_compounds.
> >>
> >> If you make a formdata:
> >>
> >>   fd = FormData(a)
> >>
> >> You get e.g. a list of functions:
> >>
> >>   fd.coefficients
> >>
> >> which have counts in [0,n),
> >> and can get the original argument (e.g. the PyDOLFIN Function)
> >> from the dict original_arguments:
> >>
> >>   for f in fd.coefficients:
> >>       original_f = fd.original_arguments[f]
> >
> > ok.
> >
> >> >> I've confusingly used the term "coefficient" in e.g.
> >> >> FormData, I guess we should stick to "function" in UFL.
> >> >> Agreed?
> >> >
> >> > Agree, but there will be a coefficient thing in the monomial
> >> > representation where functions are expanded to
> >> >
> >> >  f = f_i v_i
> >>
> >> Do you need to represent this sum explicitly?
> >> Some extension to UFL will be needed to do that.
> >
> > No, implicitly via indices.
> 
> What do you mean? Using actual indices to represent this sounds like a
> rather explicit representation :)

Yes, it will be a very explicit sum of products of basis functions.

> But I guess you're keeping your own data structure for this, so I
> don't need to care?

Yes.

-- 
Anders

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