[gecode-users] diffn constraint for Gecode

[Christian Schulte]

Hi,

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). 

The plan is to eventually improve to a state-of-the-art implementation.
Taking code directly from Jacop into Gecode will not work due to their
license. Maybe you would even be interested to contribute? At least you
would have a nice structure to start from.

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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