[CP-SAT] better expand_objective during presolve; improved implementation of obj_lb_search; refactor search code

ortools/sat/optimization.h

@@ -257,41 +257,6 @@ class CoreBasedOptimizer {
   bool stop_ = false;
 };
 
-// This class will scan the objective up from its minimal value to increase the
-// objective lower bound.
-//
-// TODO(user): Implement an acceleration schema in the LB improvements.
-class ObjectiveLowerBoundScanner {
- public:
-  ObjectiveLowerBoundScanner(
-      IntegerVariable objective_var,
-      const std::function<void()>& feasible_solution_observer, Model* model);
-
-  // Tries to shave the lower bound of the objective.
-  // It returns:
-  //   - SatSolver::INFEASIBLE if the search is done. If the solution observer
-  //     was called this actually means optimal, otherwise it means there is no
-  //     solution and it is a true infeasibility.
-  //   - SatSolver::LIMIT_REACHED if the limit stored in the model is reached.
-  SatSolver::Status ShaveObjectiveLowerBound();
-
- private:
-  // Model object.
-  Model* model_;
-  SatSolver* sat_solver_;
-  TimeLimit* time_limit_;
-  IntegerTrail* integer_trail_;
-  IntegerEncoder* encoder_;
-  const SatParameters parameters_;
-  LevelZeroCallbackHelper* level_zero_callbacks_;
-  SharedResponseManager* shared_response_manager_;
-  const IntegerVariable objective_var_;
-  const std::function<void()> feasible_solution_observer_;
-
-  // Current state of the scan.
-  int iteration_ = 0;
-};
-
 }  // namespace sat
 }  // namespace operations_research