Fix GF2 incorrectly treating some one-sided rows as equality

[aliceb-nv]

The GF2 presolver was using the wrong test to check if a Papilo row was an equality. This PR fixes this by checking the proper flags. The timeout for one GF2 test was also very slightly increased to be more robust w.r.t. CI.

Description

Issue

Checklist

• I am familiar with the Contributing Guidelines.
• Testing
  • New or existing tests cover these changes
  • Added tests
  • Created an issue to follow-up
  • NA
• Documentation
  • The documentation is up to date with these changes
  • Added new documentation
  • NA

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[aliceb-nv]

/ok to test 7558040

[coderabbitai]

📝 Walkthrough

Walkthrough

GF2 presolve now supports pinned equations and one-sided rows, validates their integer values, retains full right-hand sides, and applies parity conversion when building the binary system. GF2 termination tests use longer time limits.

Changes

GF2 presolve row handling

Layer / File(s)	Summary
Pinned-row validation cpp/src/mip_heuristics/presolve/gf2_presolve.hpp, cpp/src/mip_heuristics/presolve/gf2_presolve.cpp	GF2 presolve derives fixed row values from equality flags or exact one-sided activities. It rejects redundant, nonfinite, noninteger, and oversized values.
Parity conversion and reconstruction cpp/src/mip_heuristics/presolve/gf2_presolve.cpp, cpp/tests/mip/termination_test.cu	GF2 constraints retain full integer right-hand sides, convert them to parity when building the binary system, and use them for key-variable reconstruction. GF2 test time limits increase from 0.5 to 1.5 seconds.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested reviewers: bubullzz, nguidotti, mlubin

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 11.11% 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 clearly identifies the GF2 presolver issue and the fix for incorrect one-sided row classification.
Description check	✅ Passed	The description accurately explains the equality-row detection fix and the test timeout increase.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@cpp/src/mip_heuristics/presolve/gf2_presolve.cpp`:
- Around line 203-217: Add regression cases in gf2_presolve_test.cpp covering
pinned_row_value for RHS-pinned rows, LHS-pinned rows, and equality rows, plus a
non-pinned row that is rejected. Assert the expected pinned value or rejection
behavior while preserving the existing equality-row coverage.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

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Run ID: cc535af1-061f-48a5-aa24-d9b9129008a8

📥 Commits

Reviewing files that changed from the base of the PR and between 6f164ae and 7558040.

📒 Files selected for processing (3)

• cpp/src/mip_heuristics/presolve/gf2_presolve.cpp
• cpp/src/mip_heuristics/presolve/gf2_presolve.hpp
• cpp/tests/mip/termination_test.cu

[aliceb-nv]

/merge

[github-actions]

CI Test Summary

✅ All 31 test job(s) passed.