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

On 21 April 2010 12:09, Mehdi Nikbakht <m.nikbakht@xxxxxxxxxx> wrote:
> Hello,
>
> I am just started examining ufl to expand integrands. To perform the
> expansion, I have defined a transformation derived form
> ReusedTransformer. I succeeded expanding ufl integrands for scaler
> functions, but I encountered a problem while trying to work with vector
> functions.
>
> Assume that I have a linear form defined as,
>
> element = VectorElement("Lagrange", triangle, 1)
>
> u = TrialFunction(element)
> v = TestFunction(element)
>
> f = Coefficient(element)
> g = Coefficient(element)
>
> L = inner(f + g, v)*dx
>
> which will be interpersonal as,
> sum_{i_0} ((v_0)[i_0]) * ((w_0 + w_1)[i_0])
>
> I want to use ufl to expand linear form to,
>
> L = inner(f, v)*dx + inner(g, v)*dx
> which should be interpreted as,
>
> sum_{i_0} ((v_0)[i_0]) * ((w_0)[i_0]) + sum_{i_1} ((v_0)[i_1]) *
> (( w_1)[i_1])
>
> Now I am getting
> sum_{i_0} ((v_0)[i_0]) * ((w_0)[i_0]) + sum_{i_0} ((v_0)[i_0]) *
> (( w_1)[i_0])
>
> which fails by an error message as,
>
> FAILURE in reuse_if_possible:
> type(o) = <class 'ufl.indexsum.IndexSum'>
> operands =
>
> sum_{i_0} ((v_0)[i_0]) * ((w_0)[i_0])  + sum_{i_0} ((v_0)[i_0]) *
> ((w_1)[i_0])
>
>
> It seems to perform this extension, I need to update indices defined for
> summation. My question is how I can update an index like i_0 to i_1?

I don't see why you need one of the indices to be i_1, the above code seems to make just as much sense.
I think there is something else going wrong in your transformer class.

Kristian

> I hope that my question was clear enough.
> Mehdi
>
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