Why is my “minimum vehicles” constraint not being respected?

In the solver config, if you specify a positive weight for vehicle fixed cost as part of the objective, the minimum number of vehicles constraint is not enforced. This is a known behavior/limitation in cuOpt.

Workaround: If you need the minimum vehicles constraint to be abided by, do not include vehicle fixed cost in the objective function.

By default, cuOpt tries to minimize the number of vehicles used in the solution.