[BUG] Incorrect "MIP Infeasible" report and hanging until time limit #1021
Description
cuOpt (version 26.2.0) incorrectly reports a MIP problem as MIP Infeasible at the root relaxation stage with PDLP and concurrent mode, while the same model is successfully solved (feasible) by Gurobi. Additionally, even after declaring the status as "Infeasible", the solver fails to terminate and continues to hang until the time_limit is reached.
I put the code in the repo https://github.com/dreamaker0224/cuopt-pdlp-infeasibility-bug
Expected behavior
- cuOpt should identify the problem as Feasible, consistent with Gurobi's results.
- The solver should terminate immediately upon reaching a definitive status (Optimal/Infeasible/Error) instead of hanging until the
time_limitexpires.
Environment details:
- Environment location: Bare-metal
- OS: Ubuntu 24.04 LTS
- Hardware: AMD Ryzen 9 9900X, NVIDIA GeForce RTX 5060 Ti
- CUDA Version: 13.1
- Method of cuOpt install: pip
- cuOpt Version: 26.2.0 (git hash: f73da24)
log
Setting parameter method to 1
Setting parameter pdlp_solver_mode to 1
Setting parameter time_limit to 6.000000e+01
Setting parameter num_cpu_threads to 19
cuOpt version: 26.2.0, git hash: f73da24d, host arch: x86_64, device archs: 75-real,80-real,86-real,90a-real,100f-real,120a-real,120
CPU: AMD Ryzen 9 9900X 12-Core Processor, threads (physical/logical): 20/20, RAM: 4.28 GiB
CUDA 13.1, device: NVIDIA GeForce RTX 5060 Ti (ID 0), VRAM: 15.48 GiB
CUDA device UUID: 1e77ffffffc456-0effffff87-7dffffff92
Solving a problem with 4557 constraints, 7909 variables (1677 integers), and 2029894 nonzeros
Problem scaling:
Objective coefficents range: [3e-03, 1e+00]
Constraint matrix coefficients range: [1e-08, 1e+00]
Constraint rhs / bounds range: [0e+00, 1e+00]
Variable bounds range: [0e+00, 1e+00]
Warning: input problem contains a large range of coefficients: consider reformulating to avoid numerical difficulties.
Original problem: 4557 constraints, 7909 variables, 2029894 nonzeros
Calling Papilo presolver (git hash 741a2b9c)
Presolve status: reduced the problem
Presolve removed: 0 constraints, 1 variables, 1 nonzeros
Presolved problem: 4557 constraints, 7908 variables, 2029893 nonzeros
Papilo presolve time: 0.94
Objective offset 0.000500 scaling_factor -1.000000
Model fingerprint: 0x191824b5
Running presolve!
After cuOpt presolve: 4557 constraints, 7908 variables, objective offset 0.000500.
cuOpt presolve time: 4.64
Solving LP root relaxation in concurrent mode
Skipping column scaling
Dual Simplex Phase 1
Dual feasible solution found.
Dual Simplex Phase 2
Iter Objective Num Inf. Sum Inf. Perturb Time
0 +1.7835954622320474e-01 1917 3.11372028e+05 0.00e+00 5.88
1 +1.7815919456141577e-01 583 4.84388225e-01 0.00e+00 5.89
1000 +1.7699493384547565e-01 525 4.00978135e+00 0.00e+00 6.18
2000 -4.6686123164201447e+00 766 3.16348771e+06 0.00e+00 7.47
3000 -9.8320261494715027e+01 778 1.64323315e+09 1.00e-07 9.36
No entering variable found. Iter 3150
Scaled infeasibility 5.442293e-07
Dual infeasibility after removing perturbation 0.000000e+00
Removed perturbation of 8.58e-05.
Updated primal infeasibility: 3.825715e+08
Continuing with perturbation removed and steepest edge norms reset
No entering variable found. Iter 3150
Scaled infeasibility 5.442293e-07
Dual infeasibility 0.000000e+00
Primal infeasibility 3.825715e+08
Updates 90
Steepest edge 5.442293e-07
Root relaxation returned: INFEASIBLE
MIP Infeasible
# [Bug: Solver hangs here until 60s time_limit is reached]