Fix asynchronous clique table handoff

[hlinsen]

The root-cut generator could retain a stale null snapshot of the clique table while that table was being constructed asynchronously.

Race sequence:

• branch_and_bound_t::clique_table_ is initially null.
• An asynchronous task starts building the table.
• cut_generation_t is constructed and copies the still-null shared_ptr.
• The asynchronous task publishes the completed table.
• Root separation waits for the task, but its copied pointer remains null.
• Conflict-graph clique cuts and the conflict-graph portion of Zero-Half cuts are skipped.

Metric	Main	Clique fix	Change
Root completion	167	166	-1
Total root-time geomean, N=160	3.760 s	3.987 s	+6.02%
Total root-time mean	23.879 s	27.087 s	+3.208 s
Root gap closed, N=159	30.955%	30.986%	+0.030 pp
Root-gap better/tied/worse	—	11/140/8	Essentially neutral

Instance	Root time: main → fix	Ratio	Root gap: main → fix	Change
ns1208400	4.06 → 54.05 s	13.31×	0.000% → 0.000%	0.000 pp
proteindesign122trx11p8	7.34 → 21.46 s	2.92×	20.667% → 23.961%	+3.293 pp
proteindesign121hz512p9	10.01 → 24.29 s	2.43×	16.683% → 18.288%	+1.605 pp
comp21-2idx	14.46 → 23.62 s	1.63×	50.676% → 54.248%	+3.573 pp

Three regressions bought stronger root bounds. ns1208400 incurred the largest cost without any root-gap improvement.

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📥 Commits

Reviewing files that changed from the base of the PR and between 0d4538c and 7ce3eb2.

📒 Files selected for processing (2)

• cpp/src/cuts/cuts.hpp
• cpp/tests/mip/cuts_test.cu

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📝 Walkthrough

Walkthrough

The cut generator now retains a reference to the caller-owned clique-table pointer. A MIP regression test verifies asynchronous clique cuts on a triangle set-packing problem.

Changes

Clique-table lifecycle

Layer / File(s)	Summary
Caller-owned clique-table contract cpp/src/cuts/cuts.hpp	cut_generation_t now requires a non-const shared-pointer reference and stores that reference instead of moving a separate pointer.
Root-node clique-cut regression cpp/tests/mip/cuts_test.cu	The test configures CPU threads and verifies root LP bounds before and after asynchronous clique cuts.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 7ce3e

This localized concurrency fix ensures root separation sees the asynchronously completed clique table, restoring the intended clique and Zero-Half cut behavior without changing external interfaces or deployment requirements. No actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: aliceb-nv, mlubin, akifcorduk

🚥 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%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 2 files.	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, "Fix asynchronous clique table handoff," clearly and concisely describes the primary change.
Description check	✅ Passed	The description directly explains the asynchronous clique-table race, the affected cut generation, the fix objective, and benchmark results.
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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[hlinsen]

/ok to test 7ce3eb2

[github-actions]

CI Test Summary

✅ All 31 test job(s) passed.

[hlinsen]

/merge