When using Mixed Integer Linear Programming to find the minimum of a linear function f(x_1,...,x_n) under a set of constraints c_i(x_1,...,x_n) (equality or inequality constraints), I would like to have not only the solution and value but also the Lagrange multipliers for the constraints, namely values a_i such that, at the critical point: grad f = sum_i a_i grad c_i I imagine that the algorithm knows about them, but I can't find the relevant method to extract it.