dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

The permutation symbol should be added to UFL.

Garth

On 13/04/11 19:20, Martin Sandve Alnæs wrote:
> Python does not know anything about implicit index summation, so in your
> code e() is only called once, and reaches the else condition and thus
> returns 0.0.
> 
> Similar to as_vector, you can use the as_tensor function, since you need
> three dimensions.
> 
> Martin
> 
> On 13 April 2011 19:04, B. Emek Abali
> <question152702@xxxxxxxxxxxxxxxxxxxxx
> <mailto:question152702@xxxxxxxxxxxxxxxxxxxxx>> wrote:
> 
>     New question #152702 on DOLFIN:
>     https://answers.launchpad.net/dolfin/+question/152702
> 
>     May be a non-needed trial for some, but I try to define an
>     expression (permutation symbol)
> 
>     def e(i,j,k):
>            if (i,j,k) == (1.0,2.0,3.0): return 1.0
>            elif (i,j,k) == (2.0,3.0,1.0): return 1.0
>            elif (i,j,k) == (3.0,1.0,2.0): return 1.0
>            elif (i,j,k) == (3.0,2.0,1.0): return -1.0
>            elif (i,j,k) == (2.0,1.0,3.0): return -1.0
>            elif (i,j,k) == (1.0,3.0,2.0): return -1.0
>            else: return 0.0
> 
>     and use (with summation over indices, it is a curl operator
>     contracted with w) in the form like
> 
>     f=v[j]*w[i]*e(i,j,l)*v[l]*dx
> 
>     which raises:
>     ufl.log.UFLException: Trying to integrate expression of rank 0 with
>     free indices
> 
>     Do I have to use as_vector(...) type definition to sum with indices
>     or is there a nice possibility to let it sum over the arguments of
>     e(...) expression?
> 
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