Solved in 0 iterations and 0.02 seconds Infeasible or unbounded model

Answered

Mohamed AlAshery

• October 09, 2019 17:01

When I use Gurobi on matlab to solve a LP, I receive the following in the command window, and I want to know whether this is an issue or not? In other words, is the solution I got at the end is correct?

>> Running_Codes_2_VCG
Academic license - for non-commercial use only
Optimize a model with 77 rows, 73 columns and 149 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 1 rows and 1 columns
Presolve time: 0.00s

Solved in 0 iterations and 0.00 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 153 rows, 73 columns and 225 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 1 rows and 1 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.03 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 231 rows, 73 columns and 303 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 1 rows and 1 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 309 rows, 73 columns and 381 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 1 rows and 1 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 387 rows, 73 columns and 459 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 14 rows and 207 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 469 rows, 73 columns and 541 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 19 rows and 253 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 549 rows, 73 columns and 621 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 23 rows and 297 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 631 rows, 73 columns and 703 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 28 rows and 343 columns
Presolve time: 0.00s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 713 rows, 73 columns and 785 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 33 rows and 389 columns
Presolve time: 0.02s

Solved in 0 iterations and 0.02 seconds
Infeasible or unbounded model
Academic license - for non-commercial use only
Optimize a model with 795 rows, 73 columns and 867 nonzeros
Coefficient statistics:
Matrix range [1e+00, 1e+00]
Objective range [1e-01, 1e+01]
Bounds range [0e+00, 0e+00]
RHS range [2e+00, 5e+01]
Presolve removed 0 rows and 721 columns
Presolve time: 0.02s
Presolved: 73 rows, 74 columns, 146 nonzeros

Iteration Objective Primal Inf. Dual Inf. Time
0 -5.1220444e+03 0.000000e+00 5.968396e+01 0s
37 -2.1111904e+03 0.000000e+00 0.000000e+00 0s

Solved in 37 iterations and 0.03 seconds
Optimal objective -2.111190358e+03

0

• 

  Eli Towle

  Gurobi Staff

  • October 09, 2019 19:54

  Hi Mohamed,

  The first nine models you solve are either infeasible or unbounded. The last model you solve is feasible with an optimal objective value of -2111.190358. Is this different from what you expected?

  Thanks!

  Eli

  0
• 

  Mohamed AlAshery

  • October 09, 2019 20:02

  

  

  

  Thanks for your comment!

  They are for the same model. When I run the model, it executes multiple iterations, with each iteration saying "Infeasible or unbounded model", except the last one when it reaches a feasible solution. I hope it is clearer now.

  0
• 

  Eli Towle

  Gurobi Staff

  • October 09, 2019 20:12

  Hi Mohamed,

  Based on the log files, it looks like the MATLAB code you're running iteratively adds constraints to the model and re-solves it until the model has a finite solution. This looks normal to me. However, I can't say anything about the correctness of the MATLAB code, as this depends on the theory behind the algorithm and the correctness of the implementation.

  Thanks!

  Eli

  0
• 

  Mohamed AlAshery

  • October 09, 2019 20:24

  

  

  

  Hi Eli,

  Thank you so much for your feedback.

   

  Mohamed

  0

Please sign in to leave a comment.