For reference, I was able to work around the issue with
=============== *snip* ===============
# F = zero() * v * dx
F = u * Expression('0.0', cell=triangle) * v * dx \
+ Expression('0.0', cell=triangle) * v * dx
a = lhs(F)
L = rhs(F)
assemble(a)
assemble(L)
=============== *snap* ===============
Urgh.
--Nico
On Tue, May 28, 2013 at 9:37 PM, Nico Schlömer <[email protected]>wrote:
> Hi,
>
> when using lhs() or rhs() on an expression that happens to have no lhs or
> rhs, e.g.,
>
> { 0 } * dxeverywhere
>
> those routines will return
>
> <empty Form>
>
> When passing this to assemble(), it'll complain with
>
> ========= *snip* =========
> [...]
> RuntimeError: Form is empty. Cannot pass to JIT compiler.
> ========= *snap* =========
>
> I posted something related as a bug,
> https://bitbucket.org/fenics-project/dolfin/issue/44/assemble-0-vectors.
>
> Any quick and dirty workaround known for this? (e.g., how do I test if a
> form is empty?)
>
> --Nico
>
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