Skip to content

Wrong solution on MILP with HiGHS >= 1.13 #2980

@fontanf

Description

@fontanf

Hi,

With 1.12

Running HiGHS 1.12.0 (git hash: 755a8e027a): Copyright (c) 2025 HiGHS under MIT licence terms
Set option log_file to "HiGHS.log"
Number of BV entries in BOUNDS section is 60
Number of LI entries in BOUNDS section is 41
MIP model has 150 rows; 101 cols; 645 nonzeros; 101 integer variables (60 binary)
Coefficient ranges:
  Matrix  [1e+00, 6e+02]
  Cost    [1e+00, 1e+00]
  Bound   [1e+00, 8e+01]
  RHS     [1e+00, 2e+03]
Presolving model
140 rows, 91 cols, 615 nonzeros  0s
123 rows, 79 cols, 570 nonzeros  0s
Presolve reductions: rows 123(-27); columns 79(-22); nonzeros 570(-75) 
Objective function is integral with scale 1

Solving MIP model with:
   123 rows
   79 cols (50 binary, 29 integer, 0 implied int., 0 continuous, 0 domain fixed)
   570 nonzeros

Src: B => Branching; C => Central rounding; F => Feasibility pump; H => Heuristic;
     I => Shifting; J => Feasibility jump; L => Sub-MIP; P => Empty MIP; R => Randomized rounding;
     S => Solve LP; T => Evaluate node; U => Unbounded; X => User solution; Y => HiGHS solution;
     Z => ZI Round; l => Trivial lower; p => Trivial point; u => Trivial upper; z => Trivial zero

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work      
Src  Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

         0       0         0   0.00%   78              inf                  inf        0      0      0         0     0.0s
         0       0         0   0.00%   78              inf                  inf        0      0      3        39     0.0s
 H       0       0         0   0.00%   90.99999        167               45.51%      433     57    249       312     0.1s
 H       0       0         0   0.00%   90.99999        164               44.51%      433     57    251       312     0.1s
 H       0       0         0   0.00%   90.99999        158               42.41%      433     57    255       312     0.1s
 H       0       0         0   0.00%   90.99999        157               42.04%      433     57    261       312     0.1s
 L       0       0         0   0.00%   90.99999        119               23.53%      445     24    263       532     0.2s
        87       0        28 100.00%   119             119                0.00%      486     32    422      1942     0.2s

Solving report
  Model             model
  Status            Optimal
  Primal bound      119
  Dual bound        119
  Gap               0% (tolerance: 0.01%)
  P-D integral      0.0357993761546
  Solution status   feasible
                    119 (objective)
                    0 (bound viol.)
                    5.68434188608e-14 (int. viol.)
                    0 (row viol.)
  Timing            0.18
  Max sub-MIP depth 1
  Nodes             87
  Repair LPs        0
  LP iterations     1942
                    119 (strong br.)
                    303 (separation)
                    1183 (heuristics)

With 1.13 or 1.14

Running HiGHS 1.13.1 (git hash: 3be639f037): 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 60
Number of LI entries in BOUNDS section is 41
MIP model has 150 rows; 101 cols; 645 nonzeros; 101 integer variables (60 binary)
Coefficient ranges:
  Matrix  [1e+00, 6e+02]
  Cost    [1e+00, 1e+00]
  Bound   [1e+00, 8e+01]
  RHS     [1e+00, 2e+03]
Presolving model
140 rows, 91 cols, 615 nonzeros  0s
123 rows, 79 cols, 570 nonzeros  0s
Presolve reductions: rows 123(-27); columns 79(-22); nonzeros 570(-75) 
Objective function is integral with scale 1

Solving MIP model with:
   123 rows
   79 cols (50 binary, 29 integer, 0 implied int., 0 continuous, 0 domain fixed)
   570 nonzeros

Src: B => Branching; C => Central rounding; F => Feasibility pump; H => Heuristic;
     I => Shifting; J => Feasibility jump; L => Sub-MIP; P => Empty MIP; R => Randomized rounding;
     S => Solve LP; T => Evaluate node; U => Unbounded; X => User solution; Y => HiGHS solution;
     Z => ZI Round; l => Trivial lower; p => Trivial point; u => Trivial upper; z => Trivial zero

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work      
Src  Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

         0       0         0   0.00%   78              inf                  inf        0      0      0         0     0.0s
         0       0         0   0.00%   78              inf                  inf        0      0      3        39     0.0s
 H       0       0         0   0.00%   91.99999        319               71.16%      422     24    693      1637     0.1s
 H       0       0         0   0.00%   91.99999        286               67.83%      422     24    695      1637     0.1s
 H       0       0         0   0.00%   91.99999        235               60.85%      422     24    696      1637     0.1s
 H       0       0         0   0.00%   91.99999        205               55.12%      422     24    698      1637     0.1s
 H       0       0         0   0.00%   91.99999        201               54.23%      422     24    699      1637     0.1s
 T      19       0         4   0.07%   91.99999        194               52.58%      422     24    734      1923     0.2s
 T      28       0         6   0.08%   91.99999        193               52.33%      422     24    739      1946     0.2s
 T      32       0         8   0.08%   91.99999        186               50.54%      422     24    742      1955     0.2s
 T      41       3        11   0.09%   91.99999        185               50.27%      422     24    757      1980     0.2s
 T      43       4        12   0.09%   91.99999        184               50.00%      422     24    758      1990     0.2s
 T      53       4        13   0.09%   91.99999        171               46.20%      422     24    760      2024     0.2s
 T      68       5        18   0.15%   91.99999        163               43.56%      422     24    801      2067     0.2s
 T      88       2        25   0.40%   91.99999        156               41.03%      422     24    850      2121     0.2s
 L     104       9        29   0.71%   91.99999        128               28.13%      560     50    862      2306     0.3s
 T     269      24        78  47.80%   91.99999        122               24.59%      588     55   1057      4262     0.3s
 T     463      11       153  76.56%   93              120               22.50%      666     38   1331      5433     0.3s
       531       0       182 100.00%   120             120                0.00%      574     27   1408      5698     0.4s

Solving report
  Model             model
  Status            Optimal
  Primal bound      120
  Dual bound        120
  Gap               0% (tolerance: 0.01%)
  P-D integral      0.0775699879077
  Solution status   feasible
                    120 (objective)
                    0 (bound viol.)
                    6.39488462184e-14 (int. viol.)
                    0 (row viol.)
  Timing            0.37
  Max sub-MIP depth 1
  Nodes             531
  Repair LPs        0
  LP iterations     5698
                    2 (strong br.)
                    673 (separation)
                    2834 (heuristics)

model.txt

Metadata

Metadata

Assignees

Labels

No labels
No labels

Type

No type

Projects

No projects

Milestone

No milestone

Relationships

None yet

Development

No branches or pull requests

Issue actions