The objective bound does not move

Answered

Permanently deleted user

April 22, 2020 03:33

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I am solving a binary mixed-integer linear programming model.

Gurobi produces a very good-quality solution within 5 sec. Actually, this solution is already since in the post-processing all customer demands are fulfilled and the supply is over-supplied.

However, in the solving process, the objective bound does not move in the next 2 hr. In other words, I think the issue is that gurobi cannot prove the optimality.

My question is that is there any way to improve the objective bound quickly? Or, in other words, prove the optimality faster?

Some of the log file is attached:

Gurobi Optimizer version 9.0.1 build v9.0.1rc0 (win64)
Optimize a model with 12851 rows, 7460 columns and 45900 nonzeros
Model fingerprint: 0xf7b0225d
Variable types: 185 continuous, 7275 integer (7275 binary)
Coefficient statistics:
Matrix range [2e-01, 2e+03]
Objective range [3e-01, 1e+01]
Bounds range [1e+00, 1e+00]
RHS range [1e+00, 3e+03]
Found heuristic solution: objective 13.2000000
Presolve removed 10891 rows and 5886 columns
Presolve time: 0.08s
Presolved: 1960 rows, 1574 columns, 13340 nonzeros
Variable types: 108 continuous, 1466 integer (1466 binary)

Root relaxation: objective -4.850000e+01, 602 iterations, 0.02 seconds

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

0 0 -48.50000 0 14 13.20000 -48.50000 467% - 0s

Gurobi Optimizer version 9.0.1 build v9.0.1rc0 (win64)
Optimize a model with 12851 rows, 7460 columns and 45900 nonzeros
Model fingerprint: 0xf7b0225d
Variable types: 185 continuous, 7275 integer (7275 binary)
Coefficient statistics:
Matrix range [2e-01, 2e+03]
Objective range [3e-01, 1e+01]
Bounds range [1e+00, 1e+00]
RHS range [1e+00, 3e+03]
Found heuristic solution: objective 13.2000000
Presolve removed 10891 rows and 5886 columns
Presolve time: 0.08s
Presolved: 1960 rows, 1574 columns, 13340 nonzeros
Variable types: 108 continuous, 1466 integer (1466 binary)

Root relaxation: objective -4.850000e+01, 602 iterations, 0.02 seconds

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

0 0 -48.50000 0 14 13.20000 -48.50000 467% - 0s (### already optimal)

.......

 

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 03:14 Edited

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum. Or why not try our AI Gurobot?.
• 

  Thomas Opfer

  April 22, 2020 20:44

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  You could play around with the MIPFocus parameter: https://www.gurobi.com/documentation/9.0/refman/mipfocus.html 

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