[BUG] cuOpt MIP solver log does not report final solution

[bbozkaya]

cuOpt MIP solver log (in log file or on screen) does not report the final feasible solution upon time limit running out when root node solution process (Dual Simplex Phase 2) is still unfinished, but the primal heuristics has found a feasible solution.

This issue was encountered with a private file shared by a user, but I suspect it can be replicated when

• the MIP problem is sufficiently large or difficult and root node solve takes considerable time
• the solver is provided with a short time budget that does not allow root node solve to finish, but primal heuristics can still generate a feasible solution.

Expectation:
Log file or screen log showing the final feasible solution found by the Primal Heuristics.

This was observed when running a MIP MPS file on H100 80GB HBM3 with:

• 101983 constraints 34467 variables (34296 integers) and 303046 nonzeros

cuOpt was built from source and cuopt_cli was executed as follows:
cuopt_cli --presolve t --mip-heuristics-only f --log-file <file_name> --time-limit 900 <mps_file_name>

[nguidotti]

This can be reproduced by solving the supportcase12 instance with a very short time limit:

cuopt/cpp/build/solve_MIP --path datasets/miplib2017/supportcase12.mps.bz2 --time-limit 10