MiniZinc is a free and open-source constraint modeling language.

You can use MiniZinc to model constraint satisfaction and optimization problems
in a high-level, solver-independent way, taking advantage of a large library of
pre-defined constraints. Your model is then compiled into FlatZinc, a solver
input language that is understood by a wide range of solvers.

MiniZinc is developed at Monash University in collaboration with Data61 Decision
Sciences and the University of Melbourne.

WWW: https://www.minizinc.org/