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.