Originally posted by: SystemAdmin

[pmarley2 said:]

Hi all,

I'm running a nonlinear MIP program in CPLEX, and I'm trying to analyze the engine log for simple example sets of data for my program. I know that ILOG probably has some documentation describing the engine log, but I haven't been able to find anything; could someone let me know where this is available?

Also, could someone let me know what the columns 'Gap' and 'IInt' of the numerical table reported in the engine log mean?

Here's the engine log for my small example problem.

______________

Tried aggregator 1 time.
MIQP Presolve eliminated 12 rows and 13 columns.
Aggregator did 34 substitutions.
Number of nonzeros in lower triangle of Q = 2
Using Approximate Minimum Degree ordering
Total time for automatic ordering = 0.00 sec.
Summary statistics for factor of Q:
  Rows in Factor            = 4
  Integer space required    = 4
  Total non-zeros in factor = 6
  Total FP ops to factor    = 10
Repairing indefinite Q in the objective.
Reduced MIQP has 120 rows, 118 columns, and 278 nonzeros.
Presolve time =    0.02 sec.
Clique table members: 96.
MIP emphasis: balance optimality and feasibility.
MIP search method: dynamic search.
Parallel mode: none, using 1 thread.
Root relaxation solution time =    0.00 sec.

        Nodes                                        Cuts/
  Node  Left    Objective  IInf  Best Integer    Best Node    ItCnt    Gap

      0    0        0.0000    38                      0.0000      80       
      0    0        0.0000    42                    Cuts: 70      144       
      0    0    1729.9683    77                    Cuts: 48      223       
      0    0    1745.7907    81                    Cuts: 31      245       
      0    0    1745.7907    81                Flowcuts: 1      247       
*    0+    0                        16300.0000    1745.7907      247  89.29%
      0    2    1745.7907    81    16300.0000    1745.7907      247  89.29%
*    20+    6                        9300.0000    3380.1613      445  63.65%

Clique cuts applied:  13
Cover cuts applied:  33
Implied bound cuts applied:  2
Flow cuts applied:  1
Zero-half cuts applied:  11
Gomory fractional cuts applied:  9
_____________

Thanks
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: SystemAdmin

[MaryFenelon said:]

The node log is explained in the User Manual in Discrete Optimization->Solving Mixed Integer Programs->Progress reports: interpreting the node log section.

%Gap is the relative objective gap which goes to 0 when the optimal solution is found.  It is computed by:
(best integer - best node ) * objsen / (abs (best integer) + 1e-10) * 100.0

IInf is the number of integer infeasibilities in the node subproblem.
#CPLEXOptimizers
#DecisionOptimization