[gecode-users] Support for Gecode scheduling constraints in MiniZinc

[Guido Tack]

Hi Roberto,

Roberto Castañeda wrote:
> I am working on a MiniZinc model and I would like to access some of the Gecode
> scheduling constraints, such as the cumulative version with optional tasks.
> Currently, I just see a couple of versions of the unary constraint and
> the basic cumulatives are declared.

The cumulatives constraint checks for the special cases that correspond to unary and cumulative, so all constraints with mandatory tasks are actually available through cumulatives.  In the future, we will move the handling of the special cases into the Gecode post function for cumulatives.

> As far as I understand, one can add support for those constraints simply by
> declaring them in a .mzn file and adding the corresponding code to 
> flatzinc/registry.cpp (I have actually done that to solve my problem). Unless 
> there is some reason not to do it, I could add all versions listed in 
> http://www.gecode.org/doc-latest/reference/scheduling_8hh.html and submit a
> patch.

That's right, we can easily add support for those constraints.  What we should really do is add a definition of cumulatives with optional tasks, and then have one post function in the registry that does the specialization.  If you're willing to do that, I'll be happy to include your code.

Cheers,
	Guido

-- 
Guido Tack, http://people.cs.kuleuven.be/~guido.tack/