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Maximum Density Still Life

The MiniZinc Challenge 2010 involved comparing constraint programming solvers on various problems, with contestants like Gecode and JaCoP participating. Judges selected problems like Costas Array and Waste Water Treatment Plant Scheduling. Results for fixed, free, and parallel categorizations revealed winners like Gecode and JaCoP. Despite some solver issues, the future of Constraint Programming looks promising. The MiniZinc platform, with tools like mzn2fzn translator and Flatzinc conformance test suite, continues to evolve. Learn more at http://www.g12.csse.unimelb.edu.au/minizinc/. For positions at G12 or PhD scholarships from NICTA, contact Peter Stuckey or Mark Wallace respectively. 8

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Maximum Density Still Life

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  1. Maximum Density Still Life MiniZinc Challenge 2010 ThibautFeydy, Julien Fischer, and Peter J. Stuckey

  2. What is the MiniZinc Challenge • Comparing Constraint Programming Solvers • ~10 problems + ~100 problem instances • 3 categories • fixed search: must follow a given search strategy • free search: search anyway you want • parallel search: shared memory dual-core (free) search • non parallel solver use free results • Purse based scoring: 100 points per instance • split by speed of finding solution/proving optimality • quality of best solutions found (minimization)

  3. The problems • Satisfaction and Optimization problems • All problems are new, not previously used in MiniZinc challenge and preferably the models not seen before. • Submitted by contestants • Suggested by judges • Developed by G12 group • Problems and number of instances selected by judges • instances selected randomly

  4. The problems • Balanced academic curriculum [15] • minimization, linear + reified linear • Costas Array [5] • satisfaction, alldifferent • Depot Placement [15] • minimization, alldifferent, element, linear+reified linear • Filter Scheduling [10] • satisfaction, diffn • Crossing Minimization [5] • minimization, Boolean

  5. The problems • Ghoulomb (evil golomb rulers) [10] • minimization, cumulative • Grid colouring [5] • minimization, disjunction + reified equality • RCPSP_max (resource scheduling) [10] • minimization, cumulative • Solitaire Battleships [15] • satisfaction, reified expressions • Waste Water Treatment Plant Scheduling [10] • satisfaction, linear, disjunction + reified equality

  6. The contestants • Gecode[Fixed, Free, Par] • winner of all categories of last 2 challenges • JaCoP[Fixed] • java based CP solver • fzn2smt [Free] • translator from FlatZinc to SMTlib + SMT solver Yices • SCIP [Free] • MIP solver with propagation and learning • fzntini[Free] • Translation to SAT increasing integer sizes

  7. G12 solver entries • Cplex[Free, Par] • Cplex 12.1 applied to a linearization written in MiniZinc • G12FD [Fixed, Free] • G12 finite domain solver • Chuffed [Fixed, Free, Par] • New lazy clause generation solver

  8. Unfairness? • Linearization failed for some models • affects Cplex+ SCIP • Decomposition blew out for some models • affects Cplex, fzntini, fzn2smt • fzn2smt doesn’t appear to return answers as found (so loses potential points)

  9. Results: Fixed • Chuffed, Gecode, G12FD, JaCoP • G12FD: 1207 • JaCoP: 1579 • Gecode: 2133 • Chuffed: 4680

  10. Results: Free • Chuffed, Cplex, fzn2smt, fzntini, G12FD, Gecode, JaCoP, SCIP • SCIP: 289 • Cplex: 387 • G12FD: 525 • fzntini: 905 • JaCoP: 961 • fzn2smt: 1719 • Gecode: 1771 • Chuffed: 3341

  11. Results: Parallel • Chuffed, Cplex, fzn2smt, fzntini, G12FD, Gecode, JaCoP, SCIP • SCIP: 326 • Cplex: 500 (+113) • G12FD: 556 • fzntini: 901 • JaCoP: 997 • Gecode: 1871 (+100) • fzn2smt: 1873 • Chuffed: 2872 (-469)

  12. Parallel: • Cplex-free: 1209 vsCplex-par: 1190 • Chuffed-free: 5252 vsChuffed-par: 4347 • Gecode-free: 3105 vsGecode-par: 3994

  13. The winners: • Fixed: Gecode, JaCoP • Free: Gecode, fzn2smt, JaCoP • Parallel: fzn2smt, Gecode, JaCoP • Many thanks to our judges • Jimmy Lee • Barry O'Sullivan • Roland Yap

  14. Remarks • Immature (for CP) solvers • SCIP and CPLEX + linearization • fzn2smt Next year they will do better! • More CP Solvers • ECLiPSe+ SICStus • others promised me entries at last CP! • Rethink scoring?

  15. Future of Constraint Programming? Constraint Programming MIP SAT SMT

  16. Pessimistic Constraint Programming MIP SAT SMT Modelling layer

  17. Optimistic Constraint Programming MIP SAT SMT

  18. MiniZinc Resources • mzn2fzn translator • specializable to each FlatZinc backend • MiniZinc IDE (Eclipse based) • Flatzinc conformance test suite • Large suite of benchmarks • FlatZinc parser: yacc/lex • XML version of FlatZinc (and converters) • Courseware (some)

  19. Blatant Advertising • Get MiniZinc 1.1.6 • http://www.g12.csse.unimelb.edu.au/minizinc/ • Add some MiniZinc models to the Wiki • http://www.g12.csse.unimelb.edu.au/wiki/ • Positions available at G12 immediately: talk to • Peter Stuckey: peter.stuckey@nicta.com.au • Mark Wallace: mgw@infotech.monash.edu.au • PhD scholarships available from NICTA!

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