Gurobi freezes at root node

[Ja Ga]

Hi there,

 

I'm running some MIQP with slighly varying input. In some rare cases the solver freezes at the root node and doesn't respond anymore and doesn't make any progress either. I've tried varying some Parameters like MIPFocus=1, ImproveStartTime=100 but nothing changes. Can anyone help? The produced output is:

 

+ Solver chosen : GUROBI-GUROBI
+ Converting to real constraints
+ Processing objective function
+ Processing constraints
+ Calling GUROBI
Academic license - for non-commercial use only
Optimize a model with 31812 rows, 20981 columns and 110975 nonzeros
Model has 1031 quadratic constraints
Variable types: 20597 continuous, 384 integer (336 binary)
Coefficient statistics:
  Matrix range     [7e-07, 1e+04]
  QMatrix range    [1e+00, 1e+00]
  Objective range  [5e-06, 7e+01]
  Bounds range     [1e+00, 1e+00]
  RHS range        [1e-05, 1e+04]
Solve qcp for cone disaggregation ...
Presolve removed 29777 rows and 18904 columns
Presolve time: 0.23s
Presolved: 2508 rows, 2192 columns, 9351 nonzeros
Variable types: 2005 continuous, 187 integer (165 binary)

Root relaxation: objective -2.827695e+02, 1360 iterations, 0.03 seconds

    Nodes    |    Current Node    |     Objective Bounds      |     Work
 Expl Unexpl |  Obj  Depth IntInf | Incumbent    BestBd   Gap | It/Node Time

     0     0 -282.76951    0   46          - -282.76951      -     -    0s
     0     0 -275.32257    0   62          - -275.32257      -     -    0s
     0     0 -275.32159    0   58          - -275.32159      -     -    0s
     0     0 -272.95571    0   54          - -272.95571      -     -    0s
     0     0 -272.95533    0   52          - -272.95533      -     -    0s
     0     0 -272.28035    0   42          - -272.28035      -     -    0s
     0     0 -272.28032    0   42          - -272.28032      -     -    0s
     0     0 -272.02632    0   37          - -272.02632      -     -    0s
     0     0 -272.02616    0   37          - -272.02616      -     -    0s
     0     0 -272.00025    0   30          - -272.00025      -     -    0s

[Michael Winkler]

Could you share this model with us (best in MPS format and compresed with bzip2, 7zip, gzip or zip) or provide a link where we can download it.

Best,
Michael

[Ja Ga]

Unfortunately I can not, as I had to sign an NDA. Any guess what might be the problem?

[Michael Winkler]

Maybe it's stuck in some heuristic. You could try setting heuristics=0 . It could also be some cutting plane algorithm or just some LP solve that is numerically challenging.

Best,
Michael

[Ja Ga]

Turning off the heuristics did the job! :) Thanks a lot for the support.