int solve_subproblem(const VOL_dvector &u, const VOL_dvector &rc, double &lcost, VOL_dvector &x, VOL_dvector &v, double &pcost)
Solve the subproblem for the subgradient step.
int heuristics(const VOL_problem &p, const VOL_dvector &x, double &heur_val)
Starting from the primal vector x, run a heuristic to produce an integer solution