# Call for Problem Submission for the MiniZinc Challenge 2018

The MiniZinc Challenge is an annual solver competition in the
Constraint Programming (CP) community held before the International
Conference on Principles and Practice of Constraint Programming.
The MiniZinc Challenge 2018 is seeking interesting problem sets on
which various constraint solving technologies should be compared on
this year. Everyone is allowed to submit problems regardless of
whether they are an entrant in the challenge.

## Important dates and deadlines:

- Problem submission open: now
- Problem submission deadline:
**Sun, 20 May 2018**

## Problem submission

- Send an email with the subject line “[MZNC18] benchmark” to mzn-challenge 'at' lists.csiro.au

There are no restrictions on the kind of problems, but ideally they
should be of interesting nature such as practice-related problems and
puzzles etc. Problem submissions with real-world instances are particulary
welcome.
Models for the 2018 challenge can only use integer and Boolean
variables.

As in the last year, we anticipate local search entrants in this years
challenge again, ideally a MiniZinc model should wrap symmetry breaking
constraints in a predicate "symmetry_breaking_constraint" defined as

predicate symmetry_breaking_constraint(var bool: c) = c;

and wrap redundant constraints in a predicate "redundant_constraint" defined similarly as
predicate redundant_constraint(var bool: c) = c;

The aim of this wrapping is that local search solvers can "turn off" symmetry
breaking and redundant constraints, in order to improve solving.
The problem submitter provides a MiniZinc model of the problem and
at least 20 instances ranging from easy-to-solve to hard-to-solve for an
“ordinary” CP system. It is strongly encouraged to make use of the
global constraint definitions provided in the MiniZinc 2.1 distribution.
If you have an instance generator, we are more than happy to receive it.
Please, follow the links below for submission instructions and requirements.

www.minizinc.org/challenge2018/challenge.html

www.minizinc.org/challenge2018/rules2018.html