These are the official rules for the MiniZinc Challenge 2008.
Version 1.2
These rules were last updated on 16 June 2008.
The MiniZinc Challenge 2008 will test solvers on problems written in
MiniZinc 0.8.
Let name be the name of the solver system in what follows.
An entrant in the challenge is a constraint solver submitted in either source code or binary format.
Binary format submissions must be compatible
with the competition hardware and operating system.
Entries implemented in Java should provide a Java archive, i.e. a .jar file, plus
a shell script that invokes the solver.
Non-Java entries may also be invoked via a shell script.
Each entrant must provide a gzipped tarball containing the following:
Installation and execution of solvers must not require root access.
Binaries should be statically linked.
The organizers will make reasonable efforts to install each system, including communication with the submitters of the system in case of difficulties. Nevertheless, the organizers reserve the right to reject an entrant if its compilation or installation process proves overly difficult.
The results will be announced at CP2008. Entrants are encouraged to physically attend CP2008, but are not required to in order to participate or win.
There will be two competition CLASSES:
The README file included in the entry must specify which competition CLASS(es) the entry is to be entered in.
The problem format will be MiniZinc 0.8.
There will be some restrictions on the problems tested in this first
instance of the MiniZinc Challenge.
array[1..3] of set of 1..3: a = [{1,2}, {3}, {1,3}];
var 1..3: i;
constraint card(a[i]) > 1;
var 1..5:x;
var 1..5:y;
var 1..5:z;
constraint x <= y /\ y <= z;
solve :: int_search([x,y,z], "input_order", "indomain", "complete")
satisfy;
is correct but not
solve :: int_search([x,z], "input_order", "indomain", "complete")
satisfy;
even though most FD solvers would know the second was satisfiable.
var 1..5: x;
var 1..10: y;
constraint x > 1 -> y > 7;
constraint x = 1 -> y < 3;
solve :: int_search([x,y],"first_fail","indomain_min","complete")
maximize y;
will first label x = 1
and find maximum value y = 2
eventually on
backtracking to the choice x = 1
, then setting x >= 2
in most FD
solvers will have domains for x :: 2..5
and y :: 8..10
and this time y
will be selected as the next variable to label.
A full specification of the available choices is given in the
FlatZinc 0.8 specification.
var 1..5: x;
var 1..5: y;
constraint x < y;
solve :: int_search([x,y],"input_order","indomain","complete")
satisfy;
output ["x = ",show(x),"\ny = ",show(y),"\n"];
For optimization problems the output will also show the objective function
of the solution.
var -5..5: z = x - y;
solve :: int_search([x,y],"input_order","indomain","complete")
maximize z;
output ["%% OBJ = ",show(z),"\nx = ",show(x),"\ny = ",show(y),"\n"];
The FlatZinc 0.8 executable should output as follows:
For satisfaction the first solution found should be output using the output item. Note that in the FD search class, the first solution found is important for judging correctness of the search. If the problem is proved unsatisfiable then a single line
No solution found.
should be output.
For optimization some non standard output is required. The solver is free to output any solution via the output item of the model that it finds. It should only output solutions in increasing order of optimality. For the FD search class, the solutions must be output in the order found by the search procedure. The evaluation will use the last output solution. If the problem is proved unsatisfiable then a single line
No solution found
should be output. If the optimal solution is found, then after it is printed using the output item a single line
Optimal solution found
should be output.
Note that all output must be to the standard output.
During the Minizinc Challenge 2008 all programs will run on machines with the following specification:
If your system requires other compilers or tools please contact us and we will try to make them available.
The above machines support both 32- and 64-bit environments. Binaries may be compiled for either.
Only one core of one processor will be used for each entrant.
The benchmarks for MiniZinc Challenge 2008 (as well as for the qualification rounds) will be selected by the organizers to try to examine some of the breadth of characteristics of FD solvers.
To obtain benchmarks of suitable difficulty we will select only such instances that can be solved by at least one of the participating solvers in a sensible time-frame. For the qualification rounds no such restriction applies.
In order to collect good benchmarks each entrant is strongly encouraged to submit one or two MiniZinc 0.8 models, making use of only the globals defined in globals.mzn in that distribution, as well as some (preferably 10) instance files for each model. The instances should range from easy to hard if possible. Note that the model must conform to the problem format restrictions above.
Submitted benchmarks must be placed in the public domain.
There will be two qualification rounds. Successful participation (i.e. no incorrect results; compliance with I/O format requirements; sufficient performance) in at least one of them is mandatory to qualify for the MiniZinc Challenge 2008.
The challenge will be require solvers to process 100 Minizinc models with a run-time limit of 15 minutes (process time) per problem. The MiniZinc to FlatZinc conversion time will not be included in this, but the organizers reserve the right to penalize entries that use massively complicated globals.mzn libraries to reduce solving time.
Each solver s is run on problem p and the following information is collected.
Each problem will come with a identical total points purse totalPurse which
we assume is 2000 points which will be divided among entries as follows
(this is adapted from the SAT 2005 and SAT 2007 contests).
If no solver solves the problem then the purse is not distributed.
The totalPurse is split 50/50 into solutionPurse for solution purse and speedPurse points for speed purse.
solutionPurse = totalPurse / 2 speedPurse = totalPurse / 2
The solutionPurse is divided equally among all solvers returning a correct solution within the time limit.
solutionAward(p,s) = solutionPurse / number of solvers solving problem p
The speed purse is divided as follows. Each solver s is given a speed factor for each problem p. Times are in seconds.
speedFactor(p,s) = timeLimit(p) / (1 + timeUsed(p,s))
or 0 if solver s did not solve p.
speedAward(p,s) = speedPurse * speedFactor(p,s) / sum_s(speedFactor(p,s))
The purse is dynamically split between solution quality and speed.
Let S be the number of solvers solving the problem within the time limit.
Let O be the number of solvers returning the best objective value of any
solver.
Note that this may not be the optimum, but if one solver finds and
proves the optimal, then O is only the solvers that find and prove an optimal
solution.
The total purse is split as follows:
qualityPurse = totalPurse * S / (O + S) speedPurse = totalPurse * O / (O + S)
Note if every solver find the optimal then the purse is split equally. The rationale behind the splitting is that unless proving optimality a solver should keep trying until the time limit.
The speed purse is split between solvers that return a best solution (and prove optimality if at least one such solver did) as for satisfaction problems.
The qualityPurse is split as follows:
Let B(p) be the largest best solution found by any solver and W(p)
the smallest best solution found by any solver.
If B(p) = W(p)o the points are split equally amongst solvers that found a
solution.
Otherwise, we interpolate on a line from the best solution B(p) to
the W(p) - (B(p) - W(p)) that is the solution twice the distance from the
best to the worst solution.
qualityFactor(p,s) = solution(p,s) - (2 * W(p) - B(p))
or 0 if the solver s did not solve p
qualityAward(p,s) = qualityPurse * qualityFactor / sum_s(qualityFactor(p,s))
The rationale behind this splitting is that some of the quality points are given for achieving a solution, while the remainder are split on relative quality of solution.
The scoring calculations will be done once for each class: FD search and Free search.
The organizers may well run entrants in the FD search class on a series of smaller problems to test that they indeed are following the given search strategy. These problems will not accrue points, but may disqualify an entry from the FD search class.
The solvers will be ranked on total points awarded. There will be prizes for the three solvers with the highest scores in each of the classes: FD search and Free search. The organizers may also award prizes to the best solvers on a particular category of problems.
Due to limited computational resources, the organizers reserve the right not to accept more than one version of a particular solver (defined as sharing 50% of the source code). The organizers reserve the right to enter their own systems--or other systems of interest--to the competition, but these will not be eligible for prizes, but still will modify the scoring results.