Positive GAP interpretation when an optimal solution is found

Hi everyone:
I solved a BIP problem given 1800 seconds as a time limit. Gurobi only used less than 3 seconds to solve the model, but the Gap reported was 100%. How can I interpret the gap value different from zero, when it is supposed that the optimal solution was reached? Here is the log:

Changed value of parameter TimeLimit to 1800.0
Prev: 1e+100 Min: 0.0 Max: 1e+100 Default: 1e+100
Changed value of parameter lazyConstraints to 1
Prev: 0 Min: 0 Max: 1 Default: 0
Optimize a model with 15 rows, 770 columns and 1030 nonzeros
Variable types: 0 continuous, 770 integer (770 binary)
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e+00, 1e+00]
Bounds range [1e+00, 1e+00]
RHS range [1e+00, 1e+00]
Presolve time: 0.00s
Presolved: 15 rows, 770 columns, 1030 nonzeros
Variable types: 0 continuous, 770 integer (770 binary)

Root relaxation: objective 0.000000e+00, 15 iterations, 0.00 seconds

0 0 0.00000 0 6 - 0.00000 - - 1s
0 0 0.00000 0 7 - 0.00000 - - 1s
0 0 0.00000 0 6 - 0.00000 - - 2s
H 0 0 1.0000000 0.00000 100% - 2s

Explored 1 nodes (1596 simplex iterations) in 2.39 seconds
Thread count was 8 (of 8 available processors)

Solution count 1: 1

Optimal solution found (tolerance 1.00e-04)
Best objective 1.000000000000e+00, best bound 0.000000000000e+00, gap 100.0000%

Thanks in advance,

Official comment

Simranjit Kaur

Gurobi Staff

December 06, 2024 00:45

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?.

Eli Towle

June 17, 2020 21:56

This behavior was corrected by upgrading from Gurobi 7.5.2 to Gurobi 9.0.2.

Eli

Carlos Monardes

June 18, 2020 02:49

Thanks Eli for your help. Best regards,

Positive GAP interpretation when an optimal solution is found

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