As ILOG CPLEX solves the problem, it produces a log like the following lines:

Iteration log . . . Iteration: 0 Infeasibility = 48.000000 (5.15396e+13) Network - Optimal: Objective = 2.6900000000e+02 Solution time = 0.00 sec. Iterations = 7 (7)

This network log file differs slightly from the log files produced by other ILOG CPLEX optimizers: it contains values enclosed in parentheses that represent modified objective function values.

As long as the network optimizer has not yet found a feasible solution, we say that it is in Phase I. In Phase I, the network optimizer uses modified objective coefficients that penalize infeasibility. At its default settings, the ILOG CPLEX Network Optimizer displays the value of the objective function calculated in terms of these modified objective coefficients in parentheses in the network log file.

You can control the amount of information recorded in the network log file, just as you control the amount of information in other ILOG CPLEX log files. To record no information at all in the log file, use the command set network display 0. To display the current objective value in parentheses relative to the actual unmodified objective coefficients, use the command set network display 1. To see the display we described earlier in this section, leave the network display parameter at its default value, 2. (If you have changed the default value, you can reset it with the command set network display 2.)