ufl team mailing list archive

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

On 06/07/10 13:25, Patrick Riesen wrote:
> hello,
>
> i want to take the gradient of a coefficient with respect to some other
> quantity than the spatial coordinates (i.e. some other coefficient).
>
> i tried to construct a custom operator derived from diff() and the
> SpatialCoordinate/Derivative classes in ufl but after some point beyond
> my knowledge it always gets evaluated to zero by FFC then stops
> compiling with FFC : division by zero!
>
> does somebody of you experts know an approach to this?

Did you try using 'variable'?

    . . .
    v  = variable(v)
    f  = v*v
    df = diff(f, v)	

Garth

> many thanks and best regards,
> patrick
>
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