[BUG] Incorrect post-solve results for supportcase42

[nguidotti]

In the supportcase42 from the MIPLIB dataset, the post-solve reports the violation of constraints as well as an incorrect objective. This can be replicated by running the main branch with a short time limit.

cuopt-ref/cpp/build/solve_MIP --path datasets/miplib2017/supportcase42.mps.bz2 --time-limit 50
running file supportcase42.mps.bz2 on gpu : 0
cuOpt version: 25.10.0, git hash: ef90a38, host arch: x86_64, device archs: 90a-real
CPU: Intel(R) Xeon(R) Silver 4314 CPU @ 2.40GHz, threads (physical/logical): 16/32, RAM: 158.26 GiB
CUDA 13.0, device: NVIDIA H100 (ID 0), VRAM: 95.07 GiB
CUDA device UUID: 524162ffffffe7-5702-7fffffff8f-fffff

Unpresolved problem:: 18439 constraints, 19466 variables, 435653 nonzeros
Presolve status:: reduced the problem
Presolve removed:: 282 constraints, 283 variables, 564 nonzeros
Presolved problem:: 18157 constraints, 19183 variables, 435089 nonzeros
Third party presolve time: 0.221451
Solving a problem with 18157 constraints 19183 variables (1026 integers) and 435089 nonzeros
Objective offset -26775.000000 scaling_factor 1.000000
Free variable found! Make sure the correct bounds are given.
Running presolve!
After trivial presolve #constraints 18157 #variables 20069 objective offset -26775.000000.
Using 4 CPU threads for B&B
Solving LP root relaxation
Scaling matrix. Maximum column norm 5.562658e+01
Dual Simplex Phase 1
CPUFJ added a solution to population, solution queue size 0 with objective 39.9999
Dual feasible solution found.
Dual Simplex Phase 2
 Iter     Objective           Num Inf.  Sum Inf.     Perturb  Time
    1 +0.0000000000000000e+00       2 3.33333333e+02 1.00e-07 0.08
CPUFJ added a solution to population, solution queue size 0 with objective -26735
Failed to remove perturbation of 1.85e-04.

Root relaxation solution found in 504 iterations and 0.38s
Root relaxation objective +7.34366096e+00

Strong branching using 4 threads and 174 fractional variables
New solution from primal heuristics. Objective +1.199713e+01. Time 0.71
Running FP alone!
CPUFJ added a solution to population, solution queue size 0 with objective 38.9999
CPUFJ added a solution to population, solution queue size 0 with objective 37.9999
CPUFJ added a solution to population, solution queue size 0 with objective 36.9998
CPUFJ added a solution to population, solution queue size 0 with objective 35.9999
CPUFJ added a solution to population, solution queue size 0 with objective 34.9999
CPUFJ added a solution to population, solution queue size 0 with objective 33.9999
CPUFJ added a solution to population, solution queue size 0 with objective 32.9999
CPUFJ added a solution to population, solution queue size 0 with objective 31.9999
CPUFJ added a solution to population, solution queue size 0 with objective 30.9999
CPUFJ added a solution to population, solution queue size 0 with objective 29.9999
CPUFJ added a solution to population, solution queue size 0 with objective 28.9999
CPUFJ added a solution to population, solution queue size 0 with objective 27.9999
CPUFJ added a solution to population, solution queue size 0 with objective 26.9999
CPUFJ added a solution to population, solution queue size 0 with objective 25.9999
CPUFJ added a solution to population, solution queue size 0 with objective 24.9999
| Explored | Unexplored | Objective   |    Bound    | Depth | Iter/Node |  Gap   |    Time 
        1        1       +1.199713e+01  +7.343661e+00      1   0.0e+00     38.8%      2.08
CPUFJ added a solution to population, solution queue size 0 with objective 24.238
CPUFJ added a solution to population, solution queue size 0 with objective 23.238
CPUFJ added a solution to population, solution queue size 0 with objective 22.238
CPUFJ added a solution to population, solution queue size 0 with objective 22.2379
       48       48       +1.199713e+01  +7.343661e+00     14   4.2e-01     38.8%      3.09
CPUFJ added a solution to population, solution queue size 0 with objective 22.2378
       97       97       +1.199713e+01  +7.343661e+00     22   2.1e-01     38.8%      4.11
      146      146       +1.199713e+01  +7.343661e+00     29   1.4e-01     38.8%      5.13
      194      194       +1.199713e+01  +7.343661e+00     35   1.0e-01     38.8%      6.13
      242      242       +1.199713e+01  +7.343661e+00     41   8.3e-02     38.8%      7.14
      289      289       +1.199713e+01  +7.343661e+00     47   6.9e-02     38.8%      8.16
      337      337       +1.199713e+01  +7.343661e+00     52   5.9e-02     38.8%      9.17
      383      383       +1.199713e+01  +7.343661e+00     57   5.2e-02     38.8%     10.19
      423      423       +1.199713e+01  +7.343661e+00     60   4.7e-02     38.8%     11.21
      468      468       +1.199713e+01  +7.343661e+00     65   4.3e-02     38.8%     12.21
      516      516       +1.199713e+01  +7.343661e+00     72   3.9e-02     38.8%     13.22
      564      564       +1.199713e+01  +7.343661e+00     77   3.5e-02     38.8%     14.23
      612      612       +1.199713e+01  +7.343661e+00     82   3.3e-02     38.8%     15.24
      660      660       +1.199713e+01  +7.343661e+00     75   3.0e-02     38.8%     16.25
      708      708       +1.199713e+01  +7.343661e+00     91   2.8e-02     38.8%     17.25
      756      756       +1.199713e+01  +7.343661e+00     96   2.6e-02     38.8%     18.26
      804      804       +1.199713e+01  +7.343661e+00    101   2.5e-02     38.8%     19.27
      852      852       +1.199713e+01  +7.343661e+00    106   2.3e-02     38.8%     20.27
      900      900       +1.199713e+01  +7.343661e+00     99   2.2e-02     38.8%     21.29
      948      948       +1.199713e+01  +7.343661e+00    115   2.1e-02     38.8%     22.30
      996      996       +1.199713e+01  +7.343661e+00    120   2.0e-02     38.8%     23.31
     2000     2000       +1.199713e+01  +7.343661e+00    173   1.0e-02     38.8%     44.74
     2218     2218       +1.199713e+01  +7.343661e+00    180   9.0e-03     38.8%     49.28
Hit time limit. Stopping
FP alone finished!
Explored 2218 nodes in 49.32s.
Absolute Gap 4.653474e+00 Objective 1.1997134856410412e+01 Lower Bound 7.3436609543532541e+00
oob var 18605 val 0.000000 l 255.000000 u inf integer 1
oob var 18606 val 0.000000 l 255.000000 u inf integer 1
oob var 18863 val 0.000000 l 255.000000 u inf integer 1
oob var 18670 val 0.000000 l 255.000000 u inf integer 1
oob var 18927 val 0.000000 l 255.000000 u inf integer 1
oob var 18928 val 0.000000 l 255.000000 u inf integer 1
oob var 18929 val 0.000000 l 255.000000 u inf integer 1
oob var 19118 val 0.000000 l 255.000000 u inf integer 1
oob var 19119 val 0.000000 l 255.000000 u inf integer 1
oob var 19087 val 0.000000 l 255.000000 u inf integer 1
oob var 18637 val 0.000000 l 255.000000 u inf integer 1
oob var 18638 val 0.000000 l 255.000000 u inf integer 1
oob var 18991 val 0.000000 l 255.000000 u inf integer 1
oob var 18992 val 0.000000 l 255.000000 u inf integer 1
oob var 19181 val 0.000000 l 255.000000 u inf integer 1
oob var 19182 val 0.000000 l 255.000000 u inf integer 1
oob var 18959 val 0.000000 l 255.000000 u inf integer 1
oob var 18960 val 0.000000 l 255.000000 u inf integer 1
oob var 18702 val 0.000000 l 255.000000 u inf integer 1
oob var 18734 val 0.000000 l 255.000000 u inf integer 1
oob var 19150 val 0.000000 l 255.000000 u inf integer 1
oob var 19151 val 0.000000 l 255.000000 u inf integer 1
oob var 19055 val 0.000000 l 255.000000 u inf integer 1
oob var 19023 val 0.000000 l 255.000000 u inf integer 1
oob var 18895 val 0.000000 l 255.000000 u inf integer 1
oob var 18896 val 0.000000 l 255.000000 u inf integer 1
oob var 18897 val 0.000000 l 255.000000 u inf integer 1
oob var 18898 val 0.000000 l 255.000000 u inf integer 1
oob var 18899 val 0.000000 l 255.000000 u inf integer 1
oob var 18356 val 0.000000 l 255.000000 u inf integer 1
oob var 18323 val 0.000000 l 255.000000 u inf integer 1
oob var 18324 val 0.000000 l 255.000000 u inf integer 1
oob var 18325 val 0.000000 l 255.000000 u inf integer 1
oob var 18176 val 0.000000 l 255.000000 u inf integer 1
oob var 18177 val 0.000000 l 255.000000 u inf integer 1
oob var 18178 val 0.000000 l 255.000000 u inf integer 1
oob var 18179 val 0.000000 l 255.000000 u inf integer 1
oob var 18180 val 0.000000 l 255.000000 u inf integer 1
oob var 18181 val 0.000000 l 255.000000 u inf integer 1
oob var 18182 val 0.000000 l 255.000000 u inf integer 1
oob var 18183 val 0.000000 l 255.000000 u inf integer 1
oob var 18184 val 0.000000 l 255.000000 u inf integer 1
oob var 18185 val 0.000000 l 255.000000 u inf integer 1
oob var 18186 val 0.000000 l 255.000000 u inf integer 1
oob var 18187 val 0.000000 l 255.000000 u inf integer 1
oob var 18188 val 0.000000 l 255.000000 u inf integer 1
oob var 18189 val 0.000000 l 255.000000 u inf integer 1
oob var 18190 val 0.000000 l 255.000000 u inf integer 1
oob var 18191 val 0.000000 l 255.000000 u inf integer 1
oob var 18192 val 0.000000 l 255.000000 u inf integer 1
oob var 18193 val 0.000000 l 255.000000 u inf integer 1
oob var 18194 val 0.000000 l 255.000000 u inf integer 1
oob var 18195 val 0.000000 l 255.000000 u inf integer 1
oob var 18196 val 0.000000 l 255.000000 u inf integer 1
oob var 18197 val 0.000000 l 255.000000 u inf integer 1
oob var 18198 val 0.000000 l 255.000000 u inf integer 1
oob var 18199 val 0.000000 l 255.000000 u inf integer 1
oob var 18200 val 0.000000 l 255.000000 u inf integer 1
oob var 18201 val 0.000000 l 255.000000 u inf integer 1
oob var 18202 val 0.000000 l 255.000000 u inf integer 1
oob var 18203 val 0.000000 l 255.000000 u inf integer 1
oob var 18204 val 0.000000 l 255.000000 u inf integer 1
oob var 18255 val 0.000000 l 255.000000 u inf integer 1
oob var 18256 val 0.000000 l 255.000000 u inf integer 1
oob var 18257 val 0.000000 l 255.000000 u inf integer 1
oob var 18258 val 0.000000 l 255.000000 u inf integer 1
oob var 18259 val 0.000000 l 255.000000 u inf integer 1
oob var 18260 val 0.000000 l 255.000000 u inf integer 1
oob var 18261 val 0.000000 l 255.000000 u inf integer 1
oob var 18262 val 0.000000 l 255.000000 u inf integer 1
oob var 18263 val 0.000000 l 255.000000 u inf integer 1
oob var 18264 val 0.000000 l 255.000000 u inf integer 1
oob var 18265 val 0.000000 l 255.000000 u inf integer 1
oob var 18266 val 0.000000 l 255.000000 u inf integer 1
oob var 18267 val 0.000000 l 255.000000 u inf integer 1
oob var 18268 val 0.000000 l 255.000000 u inf integer 1
oob var 18269 val 0.000000 l 255.000000 u inf integer 1
oob var 18287 val 0.000000 l 255.000000 u inf integer 1
oob var 18288 val 0.000000 l 255.000000 u inf integer 1
oob var 18289 val 0.000000 l 255.000000 u inf integer 1
oob var 18290 val 0.000000 l 255.000000 u inf integer 1
oob var 18291 val 0.000000 l 255.000000 u inf integer 1
oob var 18292 val 0.000000 l 255.000000 u inf integer 1
oob var 18293 val 0.000000 l 255.000000 u inf integer 1
oob var 18294 val 0.000000 l 255.000000 u inf integer 1
oob var 18295 val 0.000000 l 255.000000 u inf integer 1
oob var 18300 val 0.000000 l 255.000000 u inf integer 1
oob var 18301 val 0.000000 l 255.000000 u inf integer 1
oob var 18159 val 0.000000 l 255.000000 u inf integer 1
oob var 18160 val 0.000000 l 255.000000 u inf integer 1
oob var 18161 val 0.000000 l 255.000000 u inf integer 1
oob var 18162 val 0.000000 l 255.000000 u inf integer 1
oob var 18163 val 0.000000 l 255.000000 u inf integer 1
oob var 18164 val 0.000000 l 255.000000 u inf integer 1
oob var 18165 val 0.000000 l 255.000000 u inf integer 1
oob var 18166 val 0.000000 l 255.000000 u inf integer 1
oob var 18167 val 0.000000 l 255.000000 u inf integer 1
oob var 18168 val 0.000000 l 255.000000 u inf integer 1
oob var 18169 val 0.000000 l 255.000000 u inf integer 1
oob var 18170 val 0.000000 l 255.000000 u inf integer 1
oob var 18171 val 0.000000 l 255.000000 u inf integer 1
oob var 18172 val 0.000000 l 255.000000 u inf integer 1
oob var 18173 val 0.000000 l 255.000000 u inf integer 1
oob var 18174 val 0.000000 l 255.000000 u inf integer 1
oob var 18175 val 0.000000 l 255.000000 u inf integer 1
Post-solve status:: Post solved solution violates constraints. This is most likely due to different tolerances.
Solution objective: -26735.000000 , relative_mip_gap 1.000275 solution_bound 7.343661 presolve_time 0.249292 total_solve_time 50.200501 max constraint violation 0.000000 max int violation 0.000000 max var bounds violation 255.000000 nodes 2218 simplex_iterations 20
first obj: 0.000000 last improvement of best feasible: 50.096296 last improvement after recombination: 0.000000
run_solver 50305
supportcase42.mps.bz2: solution found, obj: -26735.000000

[anandhkb]

@akifcorduk @nguidotti @rg20 Is this a MUST FIX for 25.10 or can be deferred for a hot fix ? Thanks!

@afender @chris-maes for viz

[nguidotti]

I would say that it can be a hot fix unless the solution is straightforward. If I remember correctly, supportcase42 is known to have some numerical issues.

[rg20]

Looks like its not the issue of the post solve. The variables are violating limits on the presolved problem

[rg20]

This is coming from FJ.

I am also seeing the same issue in CI.

/tmp/conda-bld-output/bld/rattler-build_libmps-parser/work/cpp/src/mip/local_search/rounding/simple_rounding_kernels.cuh:196: void cuopt::linear_programming::detail::random_rounding_kernel(cuopt::linear_programming::detail::solution_t<i_t, f_t>::view_t, unsigned long, i_t *, i_t *, i_t) [with i_t = int; f_t = double]: block: [0,0,0], thread: [0,0,0] Assertion solution.problem.check_variable_within_bounds(var_id, rounding_val)&& "Var must be within bounds" failed.