An introduction to Choco 3.0

Transcription

1 An introduction to Choco 3.0 an Open Source Java Constraint Programming Library C.Prud homme, JG. Fages EMNantes, INRIA TASC, CNRS LINA Nantes, France 16 th September th September 2013 CPSolvers 2013 Choco 1 / 22

2 The Choco constraint solver Outline 1 The Choco constraint solver 2 Inside Choco 3 Dealing with real world problems 4 The future of Choco 16 th September 2013 CPSolvers 2013 Choco 2 / 22

3 The Choco constraint solver A solver for teaching and research History 1999 a first CLAIRE impl. within the OCRE project an national initiative for an open constraint solver for both teaching and research (Nantes, Montpellier, Toulouse, Bouygues, ONERA) 2003 Choco 1.0 : a first Java implementation Portability, ease of use for newcomers, etc. Guillaume Rochart (Bouygues), Hadrien Cambazard (Grenoble INP) 2008 Choco 2.0 : a user-oriented version Separation between modeling and solving, more constraints. Charles Prud homme (EMN), Hadrien Cambazard, Arnaud Malapert (Univ. Nice) 2013 Choco 3.0 : towards efficiency and reliability! Deep code refactoring, easy-to-use (and to maintain) Charles Prud homme, Jean-Guillaume Fages (EMN), Xavier Lorca (EMN) 16 th September 2013 CPSolvers 2013 Choco 3 / 22

4 The Choco constraint solver An open constraint solver Open (online source repository a, BSD license) Readable and flexible (designed for teaching and research) Efficient and reliable (solves real world problems) More than DL ( ), worldwide Code : > 60k LOC, > 700 Classes a. github.com/chocoteam/choco3 16 th September 2013 CPSolvers 2013 Choco 4 / 22

5 The Choco constraint solver Academic users In France : Universities : Nantes, Montpellier, Paris, Rennes, Toulouse, Clermont-Ferrand Engineering schools : ENSTA, ENAC, École des Mines de Nancy, École des Mines de Nantes, ISIMA Around the world : UK : University of Glasgow Ireland : University of Cork Canada : École Polytechnique de Montreal 16 th September 2013 CPSolvers 2013 Choco 5 / 22

6 The Choco constraint solver Industrial users Big companies : Safran, Dassault, PSA Research agencies : ONERA, NASA Software and Integrators : Kls-Optim, alfaplan GmbH, Easyvirt, Hedera Technology, etc. 16 th September 2013 CPSolvers 2013 Choco 6 / 22

7 Inside Choco Outline 1 The Choco constraint solver 2 Inside Choco 3 Dealing with real world problems 4 The future of Choco 16 th September 2013 CPSolvers 2013 Choco 7 / 22

8 Inside Choco Embedded Variable Types A wide variety of variable paradigms : Integer variables Boolean variables Set variables Graph variables Real variables 16 th September 2013 CPSolvers 2013 Choco 8 / 22

9 Inside Choco A Large Choice of Implemented Constraints More than 80 available constraints in Choco : Classical arithmetic constraints : =,, <,, >,, A large set of useful global constraints : AllDifferent, GlobalCardinality, NValue, Cumulative, Diffn, Occurrence, Element, Regular, Circuit... Exclusive constraints : Tree, CostRegular, Ibex... Reified constraints : any constraint can be reified. 16 th September 2013 CPSolvers 2013 Choco 9 / 22

10 Inside Choco Discrete-continuous hybridization The Ibex global constraint : Handles numerous non linear continuous expressions +,,, /, =, <, >,,, min, max, abs, sqr, sqrt, exp, log, pow, cos, sin, tan, acos, asin, atan... Can mix integer and real variables. 16 th September 2013 CPSolvers 2013 Choco 10 / 22

11 Inside Choco Explanations Choco natively supports explained constraints. Both generic and ad hoc explanations schemas Asynchronous and lazy computation, flattened or unflattened storage Improve resolution (CBJ, DBT, path repair, LNS) Next steps : Providing feedback to the user Nogood recording / SAT Solver interaction 16 th September 2013 CPSolvers 2013 Choco 11 / 22

12 Inside Choco Search-related tools Different kinds of use : Get a solution, Enumerate all solutions, Find an optimal solution Predefined search methods : Built-in search strategies (DomWDeg, ABS, IBS, etc.) and some optimization procedures (LNS, fast restart, Last Conflict, etc.). 16 th September 2013 CPSolvers 2013 Choco 12 / 22

13 Inside Choco An intuitive user interface Use of Factories to build a model : Variables : VariableFactory, Constraints : IntConstraintFactory, LogicalConstraintFactory, SetConstraintsFactory... Strategies : IntStrategyFactory, SetStrategyFactory th September 2013 CPSolvers 2013 Choco 13 / 22

14 Inside Choco Choco diffusion Contestant within the MiniZinc Challenge (2012, 2013) JSR-331 implementation (in progress) CP-Viz interface One-sheet documentation, teaching materials, articles, demo material (> 60 examples), etc. 16 th September 2013 CPSolvers 2013 Choco 14 / 22

15 Inside Choco Langford s number problem The problem is to arrange k sets of numbers 1 to n so that each appearance of the number m is m numbers on from the last. Ex : L(k = 3, n = 9)= Solver s = new Solver ( Langford ) ; IntVar [ ] p = VF. enumeratedarray ( p, n k, 0, k n 1, s ) ; f o r ( i n t i = 0 ; i < n ; i ++) { f o r ( i n t j = 0 ; j < n ( k 1 ) ; j+=n ) { s. p o s t ( ICF. a r i t h m (VF. o f f s e t ( p [ i+j ], i +2), =, p [ i +( j+n ) ] ) ) ; } } s. p o s t ( ICF. a r i t h m ( p [ 0 ], <, p [ n k 1 ] ) ) ; s. p o s t ( ICF. a l l d i f f e r e n t ( p o s i t i o n, AC ) ) ; s. s e t ( ISF. f i r s t F a i l I n D o m a i n M a x ( p o s i t i o n ) ) ; s. f i n d S o l u t i o n ( ) ; 16 th September 2013 CPSolvers 2013 Choco 15 / 22

16 Dealing with real world problems Outline 1 The Choco constraint solver 2 Inside Choco 3 Dealing with real world problems 4 The future of Choco 16 th September 2013 CPSolvers 2013 Choco 16 / 22

17 Dealing with real world problems Attacking real world problems Entropy, Easyvirt, Hedera : data center management (VM placement), Vaberlin, GSD lab : software development, code generation, Safran, Dassault Aviation : mission planning, KLS Optim, Optilogistic : loading plans for vehicles and palettes, Biotrial, Maif : personal scheduling, Kosmos : timetabling for secondary schools, PSA : online car configuration (prototype), 16 th September 2013 CPSolvers 2013 Choco 17 / 22

18 Dealing with real world problems Entropy They like Modeling (declarative, reliable), Ad hoc constraints (simplicity), Scalability (more than 100,000 VMs). Issues Clear problem statement, Unaware of NP-hardness, Discrete-continuous hybridization, Multi-objective resolution. 16 th September 2013 CPSolvers 2013 Choco 18 / 22

19 Dealing with real world problems Discussion Few feedbacks from users only when they have trouble modeling a problem, or when there is a bug. BSD license Academic inconvenience Cannot provide professional support (heavy administration), Not interested in turnkey project (SQL, HMI) : AIMMS? 16 th September 2013 CPSolvers 2013 Choco 19 / 22

20 The future of Choco Outline 1 The Choco constraint solver 2 Inside Choco 3 Dealing with real world problems 4 The future of Choco 16 th September 2013 CPSolvers 2013 Choco 20 / 22

21 The future of Choco Current hot topics inside Choco Explanations : User-oriented explanations SAT Solver interaction Discrete-continuous bridge in practice Parallelization / distribution Robotic applications (Ibex) 16 th September 2013 CPSolvers 2013 Choco 21 / 22

22 The future of Choco Acknowledgements Thank you for your attention! Fathers Founding fathers : François Laburthe (Amadeus), Narendra Jussien (EMN, LINA) Funding fathers : École des Mines de Nantes, (Bouygues SA, Amadeus SA) 16 th September 2013 CPSolvers 2013 Choco 22 / 22