Hi Omar,
In a week or so, I think I can join you in hacking on the Indexed stuff.
There are also some other issues that need to be fixed. As Ondrej
suggests, it may be a good idea for you to start learning about the
printing system, in particular fcode. In addition, the CodePrinter
class which is the superclass of FCodePrinter should be of interest, as
the logic regarding the printing of loops is implemented there (in the
method _doprint_a_piece).
It would also be very useful, if we already start thinking about what
features we want to support. The expression you provided in the first
mail is a good example. If you can think of other examples, please post
them! Even better, if you implement the expressions as tests for the
fcode printer, we can use it as a common target when we start hacking.
Øyvind
on., 17.11.2010 kl. 17.44 +0100, skrev Omar Awile:
> Hi Øyvind, Aaron
>
> Sorry for the late reply.. it took me some time to digest all this :)
> I also went through the code in the fcode and the index* modules. I
> think it will take me considerable time to wrap my head around the
> relevant parts of the sympy code to understand how to extend it. I was
> also wondering if you guys anyway had immediate plans to extend fcode
> functionality or if for you the existing is good enough. I definitely
> would like to be involved in extending this, but it will take me some
> time to even be at the point of being able to extend the existing
> code.
>
> cheers,
>
> omar
>
>
> On Sat, Nov 13, 2010 at 20:20, Aaron S. Meurer <asmeu...@gmail.com> wrote:
> >
> > On Nov 13, 2010, at 4:23 AM, Øyvind Jensen wrote:
> >
> >> fr., 12.11.2010 kl. 11.19 -0700, skrev Aaron Meurer:
> >>> If I understand you correctly, you will implicitly sum over Symbol
> >>> indices and loop over Idx indices, right? If so, that sounds like a
> >>> good idea, except why do you want to use Symbol instead of creating a
> >>> new class?
> >>
> >> Well, maybe a new class is better, I'm not sure. The idea was to allow
> >> implicit summation with repeated indices of class Idx as it is done
> >> today, and use something else for indices that are not subject to
> >> implicit summation.
> >>
> >>>
> >>> I'm also confused about creating one class vs. another. What would
> >>> happen in your model if you mix both, like
> >>>
> >>>>>> i = Idx('i')
> >>>>>> j = Symbol('j', dimension=N, integer=True) # Or whatever you end up
> >>>>>> doing
> >>>>>> A[i, j]
> >>> ???
> >>
> >> That's a good question. Maybe there should only be one Indexed class
> >> that can handle indices of various types. It may be the cleanest
> >> approach. If I recall correctly this is the way covariant and
> >> contravariant indices are implemented in GiNaC: In addition to an Idx
> >> class, GiNaC has a VarIdx class for indices with given variance. We
> >> should also be able to follow this approach for variance, and it may be
> >> a good approach for elemental indices as well.
> >
> > I agree. Just put the type as a keyword argument to Idx, and store it as a
> > property of the element (unless the two different things really are
> > different enough that they deserve to be different classes).
> >
> > Aaron Meurer
> >
> >>
> >> To follow that approach, I think we are going to need
> >>
> >> 1) some representation of elemental indices (Symbol? ElemIdx?
> >> FixedIdx? ...)
> >> 2) improvements to sympy.tensor.indexed.Indexed
> >> 3) some changes in sympy.tensor.index_methods
> >> 4) printing of Sum in the code printers
> >>
> >> Øyvind
> >>
> >>
> >>>
> >>> Aaron Meurer
> >>
> >>
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