Horrible presolve time and bad solution

Answered

Permanently deleted user

May 18, 2020 09:35

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The log is as follows, could anyone give some suggestions on what should I do?

Gurobi 9.0.2 (win64, Matlab) logging started Mon May 18 15:23:10 2020

Gurobi Optimizer version 9.0.2 build v9.0.2rc0 (win64)
Optimize a model with 6643716 rows, 6188940 columns and 31232016 nonzeros
Model fingerprint: 0x8b7e45d3
Variable types: 2400 continuous, 6186540 integer (6186540 binary)
Coefficient statistics:
Matrix range [1e-01, 2e+03]
Objective range [3e-01, 2e+01]
Bounds range [1e+00, 1e+00]
RHS range [1e+00, 3e+03]
Found heuristic solution: objective 95.0700000
Presolve removed 6248430 rows and 1063632 columns (presolve time = 33s) ...
Presolve removed 6248430 rows and 1063632 columns (presolve time = 81s) ...
Presolve removed 6248430 rows and 1063632 columns
Presolve time: 7199.51s

Explored 0 nodes (0 simplex iterations) in 7432.19 seconds
Thread count was 1 (of 12 available processors)

Solution count 1: 95.07

Time limit reached
Best objective 9.507000000000e+01, best bound -, gap -

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 03:12 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?.
• 

  Matthias Miltenberger

  • Gurobi Staff

  May 18, 2020 17:26

  Hey Liam,

  You are trying to solve a pretty huge model, containing over 6 million binary variables and more than 30 million nonzeroes. You may want to reduce the number of presolving rounds via PrePasses=1 or Presolve=1 to reduce the time spent in presolving.

  Cheers,
  Matthias

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