Gurobi. The pre-V1 algorithms used the Julia JuMP package [1], which allows swapping of the backend solver easily. I don't think some of the functional tests w

Gurobi. The pre-V1 algorithms used the Julia JuMP package [1], which allows swapping of the backend solver easily. I don't think some of the functional tests would pass on the open source solver though (precutting and heuristics in gurobi caused a huge speed gain). The later iteration of the algorithm used the Gurobi python library directly, which is closed source. [1] https://blog.staffjoy.com/retro-on-the-julia-programming-language-7655121ea341#.l3t8azsbz https://blog.staffjoy.com/retro-on-the-julia-programming-lan...