ILOG CPLEX 11.0 User's Manual

As you can see in that example, ILOG CPLEX logs an asterisk (*) in the left-most columnfor any node where it finds an integer-feasible solution or new incumbent. In the nextcolumn, it logs the node number. It next logs the number of nodes left to explore.In the next column, Objective, ILOG CPLEX either records the objective value at thenode or a reason to fathom the node. (A node is fathomed if the solution of a subproblem atthe node is infeasible; or if the value of objective function at the node is worse than thecutoff value for branch & cut; or if the node supplies an integer solution.) This column is leftblank for lines where the first column contains an asterisk (*) indicating a node whereILOG CPLEX found an integer-feasible solution or new incumbent.In the column labeled IInf, ILOG CPLEX records the number of integer-infeasiblevariables and special ordered sets. If no solution has been found, the column titled BestInteger is blank; otherwise, it records the best integer solution found so far.The column labeled Cuts/Best Node records the best objective function value achievable.If the word Cuts appears in this column, it means various cuts were generated; if a particularname of a cut appears, then only that kind of cut was generated.The column labeled ItCnt records the cumulative iteration count of the algorithm solvingthe subproblems. Until a solution has been found, the column labeled Gap is blank. If asolution has been found, the relative gap value is printed: when it is less than 999.99, thevalue is printed; otherwise, hyphens are printed. The gap is computed as:(best integer - best node ) * objsen / (abs (best integer) + 1e-10)Consequently, the printed gap value may not always move smoothly. In particular, there maybe sharp improvements whenever a new best integer solution is found. Moreover, if thepopulate procedure is invoked, the printed gap value may become negative after the optimalsolution has been found and proven optimal.ILOG CPLEX 11.0 — USER’ S MANUAL 285