[gecode-users] Reified MiniZinc Decompositions of Globals are overridden for Gecode

[Guido Tack]

Hi,

that’s indeed a bit of a design problem in the current MiniZinc library.  We’ve got a solution for it (at the MiniZinc level, so solvers wouldn’t have to change) but it’s not fully implemented yet (it would involve having standard decompositions for all reified globals, and solvers being able to override them if they have dedicated reified constraints).

Cheers,
Guido

-- 
GUIDO TACK                  
Senior Lecturer

Information Technology
Monash University
Level 6, Room 6.40, Building H, Caulfield Campus
900 Dandenong Road
Caulfield East VIC 3145
Australia

T: +61 3 9903 1214                      
E: guido.tack at monash.edu <mailto:guido.tack at monash.edu>
http://www.csse.monash.edu/~guidot/ <http://www.csse.monash.edu/~guidot/>


> On 2 May 2016, at 7:04 PM, Alexander Schiendorfer <alexander.schiendorfer at informatik.uni-augsburg.de> wrote:
> 
> Hi everyone,
> 
> I have a question regarding the MiniZinc globals definition of lex_less (among others) in Gecode,
> in particular how their reified version is treated.
> 
> Say I wanted to solve the following model:
> 
> % test if lexless can be used in reified mode
> array[1..5] of var 0..10: x;
> array[1..5] of var 0..10: y;
> 
> include "globals.mzn";
> constraint alldifferent(x);
> 
> constraint lex_less(x, y) \/ x[1] = 9;
> solve satisfy;
> 
> 
> Since, for example, the Gecode-specific "lex_less.mzn" file overwrites all predicate definitions there, we also
> lose the "lex_less_int_reif" decomposition specified in the standard MZN-library.
> 
> Wouldn't it be nicer to have this decomposition available until there is a reified variant of "lex_less"?
> I tried copying "predicate lex_less_int_reif(...)" from "std" to Gecode's "lex_less.mzn" and it made the above
> model solvable.
> 
> Is there a particular reason for not doing this?
> 
> Cheers,
> Alex
> 
> -- 
> Alexander Schiendorfer, M.Sc.
> Institute for Software & Systems Engineering
> Raum 3043, Gebäude N
> Universität Augsburg
> 
> Web: http://www.informatik.uni-augsburg.de/lehrstuehle/swt/se/staff/aschiendorfer/
> Tel.: +49 (821) 598 - 2196
> E-Mail: alexander.schiendorfer at informatik.uni-augsburg.de
> 
> SASO’16 - Tenth IEEE International Conference on Self-Adaptive and Self Organizing Systems
> Augsburg, Germany, 12-16 September 2016
> @SASO2016Conf
> http://uni-augsburg.de/saso2016 – Submit! Announce! Participate!
> 
> 
> _______________________________________________
> Gecode users mailing list
> users at gecode.org
> https://www.gecode.org/mailman/listinfo/gecode-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.gecode.org/pipermail/users/attachments/20160503/4fb10695/attachment.html>