Gurobi presolve mistakenly reports infeasibility for a feasible instance

回答済み

Xintong Zhou

2025年06月20日 03:38

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Hi,

I am working on this small LP instance:

\* feasible *\
Minimize
OBJ: 55.59 x0 + 20.64 x1
Subject To
_C1: - 33.55 x0 + 55.79 x1 <= 4326
_C2: - 49.31 x0 + 39.55 x1 <= 3259.61
_C3: - 76.66 x0 - 42.31 x1 >= -3572.51
_C4: 79.08 x0 + 58.17 x1 >= 2720.42
_C5: 62.57 x0 - 74.56 x1 <= -343.64
_C6: 82.76 x0 - 40.36 x1 <= 855.48
Bounds
 -100 <= x0 <= 200
 -100 <= x1 <= 200
End

which is feasible, with an optimal solution (obj = 588.67) returned by gurobi by default.

However, more aggressive presolve (Presolve=2) in Gurobi reports infeasible for the same instance.

Is this expected? Any comments are appreciated. Thanks!

The log:

$> gurobi_cl Presolve=2 seed.lp
Set parameter Username
Set parameter LicenseID to value 2667871
Set parameter LogFile to value "gurobi.log"
Set parameter Presolve to value 2
Using license file /home/x27zhou/gurobi.lic
Academic license - for non-commercial use only - expires 2026-05-18

Gurobi Optimizer version 12.0.2 build v12.0.2rc0 (linux64 - "Ubuntu 22.04.5 LTS")
Copyright (c) 2025, Gurobi Optimization, LLC

Read LP format model from file seed.lp
Reading time = 0.00 seconds
OBJ: 6 rows, 2 columns, 12 nonzeros

Using Gurobi shared library /home/x27zhou/gurobi1202/linux64/lib/libgurobi.so.12.0.2

CPU model: Intel(R) Xeon(R) Gold 6348 CPU @ 2.60GHz, instruction set [SSE2|AVX|AVX2|AVX512]
Thread count: 56 physical cores, 112 logical processors, using up to 32 threads

Non-default parameters:
Presolve  2

Optimize a model with 6 rows, 2 columns and 12 nonzeros
Model fingerprint: 0x404d2dfd
Coefficient statistics:
  Matrix range     [3e+01, 8e+01]
  Objective range  [2e+01, 6e+01]
  Bounds range     [1e+02, 2e+02]
  RHS range        [3e+02, 4e+03]
Presolve removed 6 rows and 0 columns
Presolve time: 0.00s

Solved in 0 iterations and 0.00 seconds (0.00 work units)
Infeasible model

 

 

 

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  Riley Clement

  • Gurobi Staff

  2025年06月20日 04:43

  Hi Xintong,

  This is definitely unexpected.  I think the easiest way to handle this will be for me to open up a ticket in our Help Center.  You will receive an email related to this shortly - please keep an eye on junk/spam folders.

  - Riley

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  Xintong Zhou

  2025年06月20日 04:46

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  Hi Riley,

  Many thanks for your prompt reply! I will follow up the ticket.

  Xintong

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  Eli Towle

  • Gurobi Staff

  2026年03月09日 17:23

  This issue was fixed in Gurobi 12.0.3. Thanks for letting us know about it.

  0

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