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[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting Martin Sandve Alnæs <martinal@xxxxxxxxx>:

> On Tue, Mar 3, 2009 at 6:50 PM, Kristian Oelgaard
> <k.b.oelgaard@xxxxxxxxxx> wrote:
> > Quoting Martin Sandve Alnæs <martinal@xxxxxxxxx>:
> >
> >> On Tue, Mar 3, 2009 at 6:29 PM, Kristian Oelgaard
> >> <k.b.oelgaard@xxxxxxxxxx> wrote:
> >> > Quoting Martin Sandve Alnæs <martinal@xxxxxxxxx>:
> >> >
> >> >> On Tue, Mar 3, 2009 at 4:37 PM, Kristian Oelgaard
> >> >> <k.b.oelgaard@xxxxxxxxxx> wrote:
> >> >> > Quoting Martin Sandve Alnæs <martinal@xxxxxxxxx>:
> >> >> >
> >> >> >> Nothing implemented, no.
> >> >> >> I'll have to think about it.
> >> >> >>
> >> >> >> Martin
> >> >> >
> >> >> > Could someone please fill me in on the most important details of
> >> >> ListTensor?
> >> >> > Looking at the sub tree I get a strong urge to just ignoring it,
> would
> >> that
> >> >> be safe?
> >> >> >
> >> >> > Kristian
> >> >>
> >> >> I don't get what you're asking for here. Temporarily you can
> >> >> probably ignore it, but in the end it should be supported.
> >> >
> >> > I had a second look at Indexed vs. ComponentTensor (and ListTensor) and
> I
> >> think
> >> > I managed to make some sense out of it. But why does ListTensor not
> have
> >> indices
> >> > like ComponentTensor?
> >> >
> >> > Kristian
> >>
> >> Why should it have indices? It represents a tensor composed of an
> >> explicit list of arbitrary subtensors with no connection whatsoever.
> >> (If its subtensors are scalar expressions, think of it as ListVector,
> >> which it was in the first version)
> >>
> >> Example:
> >>   w = as_vector((1.0, 2.0)) # -> ListTensor((FloatValue(1.0),
> >> FloatValue(2.0))
> >>   fixed_convection = dot(w, grad(u))
> >
> > Maybe it's just because I don't see what ListTensor does which
> ComponentTensor
> > can't.
> >
> > Kristian
> 
> For starters, ComponentTensor can't represent the constant vector
> (1.0, 2.0) shown above.

A_j = j + 1 ?

> Take a scalar expression Aij with A.free_indices() being
> a superset of all indices in the MultiIndex ij, and let
>   A = ComponentTensor(Aij, ij)
> Here A represents the tensor-valued expression with components given by Aij.
> The rank of A equals len(ij).
> 
> Then assume (a, b, c) three distinct unrelated scalar expressions, and let
>   B = ListTensor(a, b, c)
> Here B represents the vector with components a, b, and c.

I'll look at it some more, but I think I've figured it out.

Kristian

> Martin
>