Number of Solutions

Gianluca Sabbatini

• July 13, 2020 05:58

Hi everyone,

After the simulation of optimization problem, Gurobi prints this in the python console:

 

# Solver Information

# ----------------------------------------------------------
Solver:
- Status: ok
Return code: 0
Message: Model was solved to optimality (subject to tolerances), and an optimal solution is available.
Termination condition: optimal
Termination message: Model was solved to optimality (subject to tolerances), and an optimal solution is available.
Wall time: 29.109039068222046
Error rc: 0
Time: 114.57288098335266
# ----------------------------------------------------------
# Solution Information
# ----------------------------------------------------------
Solution:
- number of solutions: 0
number of solutions displayed: 0

 

 

What does Gurobi want to tell me when it says that the number of solutions is zero?

Thanks in advance,

Gianluca.

0

• 

  Matthias Miltenberger

  Gurobi Staff

  • July 13, 2020 11:16

  Hi Gianluca,

  This is not a standard Gurobi output. What tool did you use to do the optimization?

  Cheers,
  Matthias

   

  0
• 

  Gianluca Sabbatini

  • July 13, 2020 11:17

  

  

  

  Pyomo environment

  0
• 

  Gianluca Sabbatini

  • July 13, 2020 11:23

  

  

  

  I enclose here the full output of the optimization problem:

   

  # ==========================================================
  # = Solver Results =
  # ==========================================================
  # ----------------------------------------------------------
  # Problem Information
  # ----------------------------------------------------------
  Problem:
  - Name: x1353727
  Lower bound: 1794548.847195477
  Upper bound: 1794548.847195477
  Number of objectives: 1
  Number of constraints: 13480377
  Number of variables: 1353727
  Number of binary variables: 5805
  Number of integer variables: 5805
  Number of continuous variables: 1347922
  Number of nonzeros: 40421871
  Sense: minimize
  # ----------------------------------------------------------
  # Solver Information
  # ----------------------------------------------------------
  Solver:
  - Status: ok
  Return code: 0
  Message: Model was solved to optimality (subject to tolerances), and an optimal solution is available.
  Termination condition: optimal
  Termination message: Model was solved to optimality (subject to tolerances), and an optimal solution is available.
  Wall time: 29.109039068222046
  Error rc: 0
  Time: 114.57288098335266
  # ----------------------------------------------------------
  # Solution Information
  # ----------------------------------------------------------
  Solution:
  - number of solutions: 0
  number of solutions displayed: 0

  0
• 

  Matthias Miltenberger

  Gurobi Staff

  • July 13, 2020 12:05

  Hmm, this looks like an issue on Pyomo's side. Can you try writing the problem to MPS format and then solving it with Gurobi directly to see whether there is something wrong.

  Cheers,
  Matthias

  0

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