Like the ILOG CPLEX simplex optimizers, the barrier optimizer records information about its progress in a log file as it works. Some users find it helpful to keep a new log file for each session. By default, ILOG CPLEX records information in a file named cplex.log.

Here is an example of a log file for a barrier optimization (without crossover):

Tried aggregator 1 time.
LP Presolve eliminated 9 rows and 11 columns.
Aggregator did 6 substitutions.
Reduced LP has 12 rows, 15 columns, and 38 nonzeros.
Presolve time =    0.00 sec.
Number of nonzeros in lower triangle of A*A' = 26
Using Approximate Minimum Degree ordering
Total time for automatic ordering = 0.00 sec.
Summary statistics for Cholesky factor:
  Rows in Factor            = 12
  Integer space required    = 12
  Total non-zeros in factor = 78
  Total FP ops to factor    = 650
 Itn      Primal Obj        Dual Obj  Prim Inf Upper Inf  Dual Inf          
   0  -1.3177911e+01  -1.2600000e+03  6.55e+02  0.00e+00  3.92e+01
   1  -4.8683118e+01  -5.4058675e+02  3.91e+01  0.00e+00  1.18e+01
   2  -1.6008142e+02  -3.5969226e+02  1.35e-13  7.11e-15  5.81e+00
   3  -3.5186681e+02  -6.1738305e+02  1.59e-10  1.78e-15  5.16e-01
   4  -4.5808732e+02  -4.7450513e+02  5.08e-12  1.95e-14  4.62e-02
   5  -4.6435693e+02  -4.6531819e+02  1.66e-12  1.27e-14  1.59e-03
   6  -4.6473085e+02  -4.6476678e+02  5.53e-11  2.17e-14  2.43e-15
   7  -4.6475237e+02  -4.6475361e+02  5.59e-13  2.99e-14  2.19e-15
   8  -4.6475312e+02  -4.6475316e+02  1.73e-13  1.55e-14  1.17e-15
   9  -4.6475314e+02  -4.6475314e+02  1.45e-13  2.81e-14  2.17e-15

Barrier - Optimal:  Objective =   -4.6475314194e+02
Solution time =    0.01 sec.  Iterations = 9