Incorrectly detected infeasibility due to presolve

[peterlietz]

Dear all,

I have encountered the following issue.

model.mps.txt
model.sol.txt

Highs 1.14.0 incorrectly declares the above problem to be infeasible.

Executing

highs model.mps

results in Status=Infeasible, while both

highs --read_solution_file model.sol model.mps

and

highs --presolve=off model.mps

result in Status=Optimal.

The model is small and well-conditioned, in my opinion.

Running HiGHS 1.14.0 (git hash: n/a): Copyright (c) 2026 under MIT licence terms
Command line parsed using CLI11 2.5.0: Copyright (c) 2017-2025 University of Cincinnati
Number of BV entries in BOUNDS section is 96
MIP model has 73 rows; 112 cols; 177 nonzeros; 96 integer variables (96 binary)
Coefficient ranges:
  Matrix  [1e+00, 1e+02]
  Cost    [0e+00, 0e+00]
  Bound   [1e+00, 2e+01]
  RHS     [1e+00, 6e+02]

Props to my coworker Ricardo Euler for first reproducing this phenomenon.

[fwesselm]

@peterlietz, thank you for reporting this. I will try to have a closer look next week.

[Opt-Mucca]

@fwesselm Sorry, I saw the PR before this issue. The proposed PR looks good to me, but dominatedColumns is always confusing to look at.

[EamonHetherton]

@Opt-Mucca just a courtesy FYI, #3091 already merged but this was not closed. looks like an oversight. I'm just going through some of the open issues.

[Opt-Mucca]

@EamonHetherton thanks!