test(c_api): skip flaky TimeLimitTestFixture MIP case (#1135)

[ramakrishnap-nv]

Summary

• Skip the c_api/TimeLimitTestFixture.time_limit/2 parametric instance (/mip/supportcase22.mps, 15s, CUOPT_METHOD_DUAL_SIMPLEX) via GTEST_SKIP().
• LP cases /0 and /1 remain enabled.

Why

The MIP case intermittently overshoots the 3s excess_allowed_time tolerance on CPU-thread-constrained CI runners. cuOptGetSolveTime() for MIP returns mip_solution_t::get_total_solve_time(), which is set in cpp/src/mip_heuristics/solver.cu:489 from a timer started in cpp/src/mip_heuristics/solve.cu:306 — before Papilo presolve. So solve_time includes Papilo presolve (OpenMP-parallel) and the post-B&B serial wind-down (branch_and_bound_status_future.get(), compute_feasibility, test_variable_bounds), neither of which is bounded by the user's time_limit setting.

On a 12-thread-visible CI runner, observed solve_time = 18.398s vs the 18s bar (15s + 3s tolerance). Solver itself respected the limit (Explored 0 nodes in 15.01s).

Full investigation and proposed fixes (measure inside the time-limited region only, or per-case tolerances) are in the issue.

Tracking: #1135.

Test plan

• Pre-commit clean (clang-format, verify-copyright, etc.)
• Local rebuild of C_API_TEST succeeds
• Verified /2 is reported as [ SKIPPED ] Disabled pending NVIDIA/cuopt#1135; /0 and /1 are unchanged in behavior
• CI green

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Reviewing files that changed from the base of the PR and between 16fb3fb and 548f611.

📒 Files selected for processing (1)

• cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp

🚧 Files skipped from review as they are similar to previous changes (1)

• cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp

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📝 Walkthrough

Walkthrough

A parameterized test in TimeLimitTestFixture.time_limit now skips a single parameter instance by calling GTEST_SKIP() when the first GetParam() string equals "/mip/supportcase22.mps", leaving other parameter cases and solver logic unchanged.

Changes

Cohort / File(s)	Summary
Test Skip Logic cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp	Added a conditional GTEST_SKIP() in TimeLimitTestFixture.time_limit to skip the specific parameter instance whose GetParam() equals "/mip/supportcase22.mps", bypassing subsequent solve and assertions for that case.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~7 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: skipping a flaky MIP test case in the C API tests with a reference to the tracking issue.
Description check	✅ Passed	The description provides clear context about why the test is being skipped, including the root cause, observed behavior on CI runners, and references to the tracking issue.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

🧹 Nitpick comments (1)

cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp (1)

54-56: Scope the skip to the single flaky parameter, not all MIP paths.

Line 54 currently skips any case with "/mip/" in the path. That’s broader than the PR intent (only /mip/supportcase22.mps with dual simplex) and could hide future MIP regressions if more params are added.

Proposed narrowing

-  if (filename.find("/mip/") != std::string::npos) {
+  const auto& relative_path = std::get<0>(GetParam());
+  if (relative_path == "/mip/supportcase22.mps" && method == CUOPT_METHOD_DUAL_SIMPLEX) {
     GTEST_SKIP() << "Disabled pending NVIDIA/cuopt#1135";
   }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp` around lines 54 -
56, The current skip checks any path containing "/mip/" via the filename
variable and is too broad; change it to only skip the specific flaky case by
checking filename for "supportcase22.mps" AND the test parameter that selects
the dual-simplex solver/method (e.g., inspect the test's solver/method parameter
or option that indicates "dual simplex" or DUAl_SIMPLEX) so only when
filename.find("supportcase22.mps") != std::string::npos && method==DUAL_SIMPLEX
(or parameter string contains "dual") you call GTEST_SKIP().

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp`:
- Around line 54-56: The current skip checks any path containing "/mip/" via the
filename variable and is too broad; change it to only skip the specific flaky
case by checking filename for "supportcase22.mps" AND the test parameter that
selects the dual-simplex solver/method (e.g., inspect the test's solver/method
parameter or option that indicates "dual simplex" or DUAl_SIMPLEX) so only when
filename.find("supportcase22.mps") != std::string::npos && method==DUAL_SIMPLEX
(or parameter string contains "dual") you call GTEST_SKIP().

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 0c002b6 and 16fb3fb.

📒 Files selected for processing (1)

• cpp/tests/linear_programming/c_api_tests/c_api_tests.cpp

[chris-maes]

LGTM

[ramakrishnap-nv]

/merge