[gecode-users] diffn constraint for Gecode

[Sandro Pirkwieser]

Dear Christian,

> Co-incidence: I have been adding a naïve (but better than the decomposition)
> version of the constraint to Gecode recently. I will move that code to the
> trunk this week (there are still some glitches to fix before that). 

now that's convenient!
On which algorithm is it based?

> The plan is to eventually improve to a state-of-the-art implementation.

This sounds good.
Would you consider the sweep algorithm proposed by Beldiceanu and
Carlsson as state-of-the-art, or are there any alternatives? Btw do you
know which one is applied in JaCoP?

> Taking code directly from Jacop into Gecode will not work due to their
> license.

The intention was more to get an inspiration. Anyway, both frameworks
probably differ too much.

> Maybe you would even be interested to contribute? At least you
> would have a nice structure to start from.

Yes, we can indeed think about this. Though I am not yet in a state
where I can "hack" something into Gecode, it would be a good opportunity
to start doing so.

Best regards,
Sandro

> We will release soonish a new version that will incorporate that but there
> are more things to be done before a release.
> 
> Best
> Christian
> 
> --
> Christian Schulte, KTH, web.it.kth.se/~cschulte/
> 
> 
> -----Original Message-----
> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
> Of Sandro Pirkwieser
> Sent: Wednesday, May 25, 2011 9:01 PM
> To: users at gecode.org
> Subject: [gecode-users] diffn constraint for Gecode
> 
> Hello,
> 
> I'm using Gecode to tackle a 2D packing subproblem inside an optimization
> problem. The subproblem is about packing rectangles (for the meantime
> without rotation) into a given larger rectangle and many instances of
> moderate size need to be solved. Fortunately I was able to start with the
> perfect-square example, where the adapted variant already performs quite
> good (using the cumulatives constraint). Also enabling branching on
> intervals yielded a speed-up. Now I was wondering if someone of you already
> implemented a suitable diffn constraint (see
> http://www.emn.fr/z-info/sdemasse/gccat/Cdiffn.html) in Gecode. In this way
> the non-overlapping part would (presumably) be tackled more efficiently and
> give an additional performance boost. Do you think having a look at the
> diff/diff2 implementation in JaCoP is useful for implementing it in Gecode?
> Thanks!
> 
> Best regards,
> Sandro
> 
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