Exploit dual degeneracy to reduce the number of integer infeasibilities; add primal simplex - #1685

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chris-maes wants to merge 38 commits into

NVIDIA:mainfrom

chris-maes:dual_degenerate

Commits on Jul 20, 2026

Fix bugs causing primal simplex to cycle. Enable primal simplex cleanup after dual simplex
chris-maes
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63d1ba4

Commits on Jul 21, 2026

Primal simplex pivots on dual degenerate problems to reduce integer infeasibility
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8b1e60b
First stab at using the feasibility pump on a reduced problem on the optimal face
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17b2725

Commits on Jul 24, 2026

Add check for fast pivot using slacks
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ff6f460
Merge remote-tracking branch 'origin/main' into dual_degenerate
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5e31f6c

Commits on Jul 27, 2026

Enable primal simplex. Solves 85/93 NETLIB LPs in under 1 minute
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900805a

Commits on Jul 28, 2026

Use primal simplex to remove a perturbation from dual simplex
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efc9fb0

Commits on Jul 29, 2026

Clean up logging of degenerate feasibility pump
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cf3d4d4
Add work estimates to primal simplex
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a7cfd19
Display work estimate and simplex iterations
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6dfebbf

Commits on Aug 4, 2026

Primal in crossover. Crossover tolerance mismatch fix. Pipe work estimates for root relaxation. Add initial perturbation parameter
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99d7ead

Commits on Aug 6, 2026

Merge remote-tracking branch 'cuopt-nvidia/main' into dual_degenerate
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adcb8c2
Address coderabbit review comments
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0cfc746
Address coderabbit review comments
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1c2c01a
Use tight tol for reduced costs zero check
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b2de00d
Try to clean up normalization
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a92825c
Remove AI slop
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31436ba
Style fixes
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ef75207
Fix work estimate bug in BFRT. And improve work estimates
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117b2b4

Commits on Aug 7, 2026

Harris ratio test; timers in primal; limit feasibility pump to do less work than root relaxation
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99207b2

Commits on Aug 8, 2026

Add reduced cost bounds table. Change objective in feasibility pump. Fix work limit in feasibility pump. Check for reduced cost violation before calling primal simplex. Check if we reduced number o…
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eb47c20

Commits on Aug 12, 2026

V3 of pump and pivots, better work estimates, also exploit primal degeneracy
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7641ad3

Commits on Aug 14, 2026

Devex pricing in primal; try to remove perturbations in dual
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39cb576

Commits on Aug 26, 2026

Commits on Aug 27, 2026

Have BFRT decide on bound flips
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36ca4d3

Commits on Aug 28, 2026

Improve BFRT work estimates
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75a1e97
Merge remote-tracking branch 'cuopt-nvidia/main' into dual_degenerate
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47e0848

Commits on Aug 29, 2026

Fix bug in not handling concurrent halt. Use zero_tol in step-length computation to try to remain dual feasible
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d983159

Commits on Sep 3, 2026

Style fixes
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bfcbb15
Prefer large pivots with Harris ratio buckets
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c3a0251
Add parameters to control degenerate pivots
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ef5ff66
Style fixes
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2e02e23

Commits on Sep 4, 2026

Snapshot slack columns for branch-and-bound workers
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0f95053