Gurobi reports UNKNOWN_RESULT_STATUS when Solution count = 10

WalterMadelim
Fri, 12 Sep 2025 05:18:40 +0000
Optimization (Mathematical)

I cannot figure out why the JuMP.primal_status(model) is UNKNOWN_RESULT_STATUS here

julia> model # a model that is solved before and modified
A JuMP Model
├ solver: Gurobi
├ objective_sense: MIN_SENSE
│ └ objective_function_type: JuMP.AffExpr
├ num_variables: 284616
├ num_constraints: 431774
│ ├ ...
...

julia> JuMP.optimize!(model)
Gurobi Optimizer version 12.0.2 build v12.0.2rc0 (win64 - Windows 11.0 (26100.2))

CPU model: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz, instruction set [SSE2|AVX|AVX2|AVX512]
Thread count: 4 physical cores, 8 logical processors, using up to 8 threads

Non-default parameters:
TimeLimit  120

Optimize a model with 154408 rows, 284616 columns and 882830 nonzeros
Model fingerprint: 0x154f3acc
Variable types: 174000 continuous, 110616 integer (110616 binary)
Coefficient statistics:
  Matrix range     [9e-01, 2e+01]
  Objective range  [1e+01, 3e+01]
  Bounds range     [1e+00, 6e+01]
  RHS range        [1e+00, 1e+05]

Processing MIP start from previous solve: 0 nodes explored in subMIP, total elapsed time 5s
MIP start from previous solve produced solution with objective 3.60589e+06 (5.04s)
MIP start from previous solve produced solution with objective 3.60589e+06 (5.09s)
Loaded MIP start from previous solve with objective 3.60589e+06
Processed MIP start in 5.10 seconds (4.05 work units)

Presolve removed 1905 rows and 5225 columns
Presolve time: 1.55s
Presolved: 152503 rows, 279391 columns, 863091 nonzeros
Variable types: 172314 continuous, 107077 integer (107077 binary)
Deterministic concurrent LP optimizer: primal simplex, dual simplex, and barrier
Showing barrier log only...

Root barrier log...

Ordering time: 0.08s

Barrier statistics:
 AA' NZ     : 4.064e+05
 Factor NZ  : 2.694e+06 (roughly 150 MB of memory)
 Factor Ops : 1.249e+08 (less than 1 second per iteration)
 Threads    : 2

                  Objective                Residual
Iter       Primal          Dual         Primal    Dual     Compl     Time
   0   1.86652623e+10 -1.75398155e+08  2.11e+08 0.00e+00  2.07e+06     8s
......
  30   3.53257740e+06  3.53257740e+06  9.80e-12 1.42e-13  1.88e-11    11s

Barrier solved model in 30 iterations and 11.04 seconds (9.03 work units)
Optimal objective 3.53257740e+06


Root crossover log...

   11696 DPushes remaining with DInf 0.0000000e+00                11s
       0 DPushes remaining with DInf 0.0000000e+00                11s

   18701 PPushes remaining with PInf 0.0000000e+00                11s
       0 PPushes remaining with PInf 0.0000000e+00                12s

  Push phase complete: Pinf 0.0000000e+00, Dinf 9.6187894e-11     12s


Root simplex log...

Iteration    Objective       Primal Inf.    Dual Inf.      Time
   29843    3.5325774e+06   0.000000e+00   0.000000e+00     12s
Concurrent spin time: 0.61s (can be avoided by choosing Method=3)

Solved with barrier
   29843    3.5325774e+06   0.000000e+00   0.000000e+00     13s

Root relaxation: objective 3.532577e+06, 29843 iterations, 5.63 seconds (3.26 work units)
Total elapsed time = 15.49s (DegenMoves)

    Nodes    |    Current Node    |     Objective Bounds      |     Work
 Expl Unexpl |  Obj  Depth IntInf | Incumbent    BestBd   Gap | It/Node Time

     0     0 3532577.40    0 5404 3605888.90 3532577.40  2.03%     -   16s
H    0     0                    3548146.6821 3532577.40  0.44%     -   17s
     0     0 3533464.00    0 5928 3548146.68 3533464.00  0.41%     -   22s
H    0     0                    3547803.3639 3533464.00  0.40%     -   24s
H    0     0                    3547721.3895 3533464.00  0.40%     -   25s
     0     0 3533938.63    0 6123 3547721.39 3533938.63  0.39%     -   27s
     0     0 3534118.30    0 6225 3547721.39 3534118.30  0.38%     -   29s
     0     0 3534348.21    0 6312 3547721.39 3534348.21  0.38%     -   31s
     0     0 3534363.63    0 6393 3547721.39 3534363.63  0.38%     -   32s
     0     0 3534364.65    0 6419 3547721.39 3534364.65  0.38%     -   34s
     0     0 3534364.88    0 6433 3547721.39 3534364.88  0.38%     -   35s
     0     0 3535004.49    0 6191 3547721.39 3535004.49  0.36%     -   41s
H    0     0                    3544867.0580 3535004.55  0.28%     -   42s
     0     0 3535167.41    0 6125 3544867.06 3535167.41  0.27%     -   45s
     0     0 3535261.79    0 6180 3544867.06 3535261.79  0.27%     -   47s
     0     0 3535316.12    0 6357 3544867.06 3535316.12  0.27%     -   48s
     0     0 3535322.42    0 6424 3544867.06 3535322.42  0.27%     -   49s
     0     0 3535323.29    0 6461 3544867.06 3535323.29  0.27%     -   50s
     0     0 3535490.20    0 6092 3544867.06 3535490.20  0.26%     -   60s
H    0     0                    3543860.8838 3535490.22  0.24%     -   62s
H    0     0                    3543833.9358 3535490.22  0.24%     -   64s
     0     0 3535532.34    0 6307 3543833.94 3535532.34  0.23%     -   65s
     0     0 3535559.39    0 6304 3543833.94 3535559.39  0.23%     -   66s
     0     0 3535565.03    0 6378 3543833.94 3535565.03  0.23%     -   67s
     0     0 3535566.11    0 6439 3543833.94 3535566.11  0.23%     -   67s
     0     0 3535670.38    0 6126 3543833.94 3535670.38  0.23%     -   79s
H    0     0                    3542615.0971 3535670.38  0.20%     -   81s
H    0     0                    3542344.1418 3535670.38  0.19%     -   84s
     0     0 3535702.72    0 6146 3542344.14 3535702.72  0.19%     -   85s
     0     0 3535718.84    0 6228 3542344.14 3535718.84  0.19%     -   86s
     0     0 3535722.77    0 6310 3542344.14 3535722.77  0.19%     -   86s
     0     0 3535723.49    0 6345 3542344.14 3535723.49  0.19%     -   87s
     0     0 3535749.91    0 6304 3542344.14 3535749.91  0.19%     -   92s
     0     0 3535761.89    0 6384 3542344.14 3535761.89  0.19%     -   95s
     0     0 3535763.94    0 6468 3542344.14 3535763.94  0.19%     -   96s
     0     0 3535764.43    0 6505 3542344.14 3535764.43  0.19%     -   96s
     0     0 3535785.44    0 6344 3542344.14 3535785.44  0.19%     -  101s
H    0     0                    3542148.8408 3535785.45  0.18%     -  109s
     0     0 3535790.28    0 6352 3542148.84 3535790.28  0.18%     -  110s
     0     0 3535791.24    0 6435 3542148.84 3535791.24  0.18%     -  111s
     0     0 3535804.07    0 6325 3542148.84 3535804.07  0.18%     -  116s

Cutting planes:
  Learned: 1
  Gomory: 108
  Cover: 247
  Implied bound: 129
  Clique: 25
  MIR: 9707
  StrongCG: 9
  Flow cover: 6221
  GUB cover: 8
  Zero half: 7
  Mod-K: 1
  RLT: 130
  Relax-and-lift: 588
  BQP: 1

Explored 1 nodes (135082 simplex iterations) in 120.13 seconds (115.52 work units)
Thread count was 8 (of 8 available processors)

Solution count 10: 3.54215e+06 3.54234e+06 3.54262e+06 ... 3.60589e+06

Time limit reached
Warning: max constraint violation (1.9111e-06) exceeds tolerance
Warning: max bound violation (1.2831e-06) exceeds tolerance
Best objective 3.542148840800e+06, best bound 3.535804097091e+06, gap 0.1791%

User-callback calls 8145, time in user-callback 0.03 sec

julia> JuMP.termination_status(model), JuMP.primal_status(model)
(MathOptInterface.TIME_LIMIT, MathOptInterface.UNKNOWN_RESULT_STATUS)

As you can see, although TimeLimit is reached, 10 solutions are already available.

To introduce the model above before optimize!, run this source
Summary (click for more details)
In less than 20 minutes, you can see ERROR: man interrupt (me introduced manual ERROR to facilitate debugging). Then you type model in REPL to recover the aforesaid phenomenon.

4 posts - 2 participants