ILOG CPLEX 10.2 User's Manual > Continuous Optimization > Solving LPs: Barrier Optimizer > Interpreting the Barrier Log File

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. In the:

You can control the level of information that ILOG CPLEX records about barrier optimization by setting the BarDisplay parameter. Those settings appear in Table 9.4.

Table 9.4 BarDisplay Parameter Settings
BarDisplay Values 
Meaning 
no display 
display normal information (default) 
display detailed (diagnostic) output 

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

The opening lines of that log file record information about preprocessing by the ILOG CPLEX presolver and aggregator. After those preprocessing statistics, the next line records the number of nonzeros in the lower triangle of a particular matrix, AAT, denoted A*A' in the log file.