============================================================ iZplus (fzn_izplus) -- iZ based solver for MiniZinc Challenge 2014 -- Copyright (C) 2014 NTT DATA SEKISUI SYSTEMS CORPORATION. ============================================================ * What is fzn_izplus fzn_izplus is a FlatZinc solver using iZ-C constraint programming library which is developed by NTT DATA SEKISUI SYSTEMS CORPORATION. iZ-C provides : * many built-in constraints * constraint propagation mechanism * simple search strategy And in fzn_izplus, following algorithms are 'plus'ed. * Randomized restarting in search For fast random number generation, Xorshift128 algorithm is used. http://www.jstatsoft.org/v08/i14/paper * Local search for optimization problem In real world problems, sometimes finding 'good' solution using short time is more important than finding 'best' solution using long time. And it is known empirically that 'good' solutions are similar to each other, then local search can be a good strategy. For optimization problem, fzn_izplus tries to find first solution using constraint propagation and search. After one solution was found, it searches similar solutions better than first one. * Local search for satisfying problem In parallel mode, one thread is used for local search. (Maxmizing count of assinged variables without conflict) In single thread mode, two strategies (local and normal search) are used alternately. * Variable reordering Failures occured while searching are recorded and variable selection order is changed using this information. * NG learning NG learning is implemented as described in: http://ijcai.org/papers07/Papers/IJCAI07-019.pdf (To keep NG set small, inactive NGs are removed from learnt set.) * Author Toshimitsu FUJIWARA developer at NTT DATA SEKISUI SYSTEMS CORPORATION * Acknowledgement FlatZinc parser in fzn_izplus is based on 'FlatZinc parser skeleton' written by Guido Tack. http://www.gecode.org/flatzinc.html/ Please refer to header files in flatzinc_skeleton-1.3.zip About its copyright and license. (It's contained in this archive.) Special thanks to Guido Tack and Gecode team. iZ-C is a constraint programming library developed by NTT DATA SEKISUI SYSTEMS CORPORATION. http://www.constraint.org/ja/izc_download.html (Sorry, above web page is NOT written in English.)