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Feat/956 compute iis highs - #957

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@lisazeyen

@lisazeyen lisazeyen commented Sep 15, 2026

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Closes #956 (if applicable).

Changes proposed in this Pull Request

Adds HiGHS support to Model.compute_infeasibilities(), which previously only worked with
Gurobi and Xpress. HiGHS's IIS (irreducible infeasible subsystem) computation
is documented at
HiGHS: Advanced features — IIS
and exposed in highspy via Highs.getIis().

Extended testing in test/test_infeasibility.py and test/test_optimization.py::test_infeasible_model for Highs

Checklist

  • AI-generated content is marked (see AGENTS.md).
  • Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
  • Unit tests for new features were added (if applicable).
  • A note for the release notes doc/release_notes.rst of the upcoming release is included.
  • I consent to the release of this PR's code under the MIT license.

@github-actions

github-actions Bot commented Sep 15, 2026

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Build cost — v1 vs legacy

v1 build peak & time relative to legacy, on this commit — not a comparison against master (that is CodSpeed).

peak — v1 / legacy time — v1 / legacy
peak v1/legacy time v1/legacy
Full table (time + peak, mean)
benchmarks/drivers/test_build.py::test_build[basic-n=10]
                  time (s)         peak (KiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.08815 (1.08)   │   15.03 (1.00) 
 (v1)        0.08145 (1.0)   │    15.00 (1.0) 

benchmarks/drivers/test_build.py::test_build[basic-n=250]
                  time (s)         peak (MiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.09454 (1.08)   │   12.04 (1.00) 
 (v1)        0.08746 (1.0)   │    12.04 (1.0) 

benchmarks/drivers/test_build.py::test_build[cumsum-severity=0]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.03813 (1.09)   │   15.20 (1.0) 
 (v1)        0.03487 (1.0)   │   15.20 (1.0) 

benchmarks/drivers/test_build.py::test_build[cumsum-severity=100]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.05415 (1.12)   │   44.93 (1.0) 
 (v1)        0.04838 (1.0)   │   44.93 (1.0) 

benchmarks/drivers/test_build.py::test_build[cumsum-severity=50]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.04183 (1.10)   │   11.51 (1.0) 
 (v1)        0.03815 (1.0)   │   11.51 (1.0) 

benchmarks/drivers/test_build.py::test_build[expression_arithmetic-n=10]
                  time (s)         peak (KiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.09874 (1.05)   │   24.34 (1.06) 
 (v1)        0.09373 (1.0)   │    23.04 (1.0) 

benchmarks/drivers/test_build.py::test_build[expression_arithmetic-n=250]
                 time (s)         peak (MiB) 
 name                mean   │           mean 
─────────────────────────────────────────────
 (legacy)   0.1086 (1.06)   │   16.12 (1.00) 
 (v1)        0.1025 (1.0)   │    16.12 (1.0) 

benchmarks/drivers/test_build.py::test_build[knapsack-n=10000]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.02353 (1.06)   │   752.18 (1.10) 
 (v1)        0.02213 (1.0)   │    685.15 (1.0) 

benchmarks/drivers/test_build.py::test_build[knapsack-n=100]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.02311 (1.06)   │   3.12 (1.33) 
 (v1)        0.02175 (1.0)   │    2.34 (1.0) 

benchmarks/drivers/test_build.py::test_build[kvl_cycles-severity=0]
                  time (s)          peak (MiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.06407 (1.24)   │   126.16 (1.44) 
 (v1)        0.05186 (1.0)   │     87.71 (1.0) 

benchmarks/drivers/test_build.py::test_build[kvl_cycles-severity=100]
                  time (s)          peak (MiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.06296 (1.23)   │   126.16 (1.44) 
 (v1)        0.05118 (1.0)   │     87.71 (1.0) 

benchmarks/drivers/test_build.py::test_build[kvl_cycles-severity=50]
                  time (s)          peak (MiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.06347 (1.23)   │   126.16 (1.44) 
 (v1)        0.05179 (1.0)   │     87.71 (1.0) 

benchmarks/drivers/test_build.py::test_build[masked-n=100]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.05442 (1.02)   │    715.12 (1.0) 
 (v1)        0.05338 (1.0)   │   787.73 (1.10) 

benchmarks/drivers/test_build.py::test_build[masked-n=10]
                 time (s)        peak (KiB) 
 name                mean   │          mean 
────────────────────────────────────────────
 (legacy)   0.0531 (1.10)   │   4.54 (1.27) 
 (v1)       0.04847 (1.0)   │    3.57 (1.0) 

benchmarks/drivers/test_build.py::test_build[merge_balance-severity=0]
                 time (s)          peak (KiB) 
 name                mean   │            mean 
──────────────────────────────────────────────
 (legacy)   0.3725 (1.04)   │   704.12 (1.09) 
 (v1)        0.3581 (1.0)   │    643.85 (1.0) 

benchmarks/drivers/test_build.py::test_build[merge_balance-severity=100]
                 time (s)        peak (MiB) 
 name                mean   │          mean 
────────────────────────────────────────────
 (legacy)   0.3913 (1.04)   │   18.34 (1.0) 
 (v1)        0.3769 (1.0)   │   18.34 (1.0) 

benchmarks/drivers/test_build.py::test_build[merge_balance-severity=50]
                 time (s)       peak (MiB) 
 name                mean   │         mean 
───────────────────────────────────────────
 (legacy)   0.3875 (1.05)   │   9.54 (1.0) 
 (v1)        0.3705 (1.0)   │   9.54 (1.0) 

benchmarks/drivers/test_build.py::test_build[milp-n=10]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.07464 (1.08)   │   3.77 (1.12) 
 (v1)        0.06916 (1.0)   │    3.37 (1.0) 

benchmarks/drivers/test_build.py::test_build[milp-n=50]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.07793 (1.12)   │   216.59 (1.10) 
 (v1)        0.06953 (1.0)   │    196.23 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance-severity=0]
                  time (s)         peak (KiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.03819 (1.09)   │   938.49 (1.0) 
 (v1)        0.03504 (1.0)   │   938.49 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance-severity=100]
                  time (s)       peak (MiB) 
 name                 mean   │         mean 
────────────────────────────────────────────
 (legacy)   0.03916 (1.09)   │   9.66 (1.0) 
 (v1)        0.03595 (1.0)   │   9.66 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance-severity=50]
                  time (s)       peak (MiB) 
 name                 mean   │         mean 
────────────────────────────────────────────
 (legacy)   0.03896 (1.10)   │   5.32 (1.0) 
 (v1)        0.03553 (1.0)   │   5.32 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance_sparse-severity=0]
                  time (s)       peak (MiB) 
 name                 mean   │         mean 
────────────────────────────────────────────
 (legacy)   0.02118 (1.01)   │   1.47 (1.0) 
 (v1)        0.02094 (1.0)   │   1.47 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance_sparse-severity=100]
                  time (s)       peak (MiB) 
 name                 mean   │         mean 
────────────────────────────────────────────
 (legacy)   0.02109 (1.01)   │   1.47 (1.0) 
 (v1)        0.02087 (1.0)   │   1.47 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance_sparse-severity=50]
                 time (s)       peak (MiB) 
 name                mean   │         mean 
───────────────────────────────────────────
 (legacy)   0.0211 (1.01)   │   1.47 (1.0) 
 (v1)       0.02094 (1.0)   │   1.47 (1.0) 

benchmarks/drivers/test_build.py::test_build[piecewise-n=1000]
                 time (s)          peak (KiB) 
 name                mean   │            mean 
──────────────────────────────────────────────
 (legacy)   0.1871 (1.05)   │   946.85 (1.06) 
 (v1)        0.1784 (1.0)   │    891.54 (1.0) 

benchmarks/drivers/test_build.py::test_build[piecewise-n=10]
                 time (s)         peak (KiB) 
 name                mean   │           mean 
─────────────────────────────────────────────
 (legacy)   0.1826 (1.04)   │   12.01 (1.00) 
 (v1)        0.1756 (1.0)   │    11.99 (1.0) 

benchmarks/drivers/test_build.py::test_build[qp-n=1000]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.04743 (1.07)   │   147.70 (1.06) 
 (v1)        0.04449 (1.0)   │    139.87 (1.0) 

benchmarks/drivers/test_build.py::test_build[qp-n=10]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.04681 (1.07)   │   2.60 (1.09) 
 (v1)        0.04386 (1.0)   │    2.38 (1.0) 

benchmarks/drivers/test_build.py::test_build[rolling-severity=0]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.03876 (1.08)   │   696.75 (1.03) 
 (v1)        0.03597 (1.0)   │    673.70 (1.0) 

benchmarks/drivers/test_build.py::test_build[rolling-severity=100]
                  time (s)         peak (MiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.08287 (1.01)   │   137.97 (1.0) 
 (v1)        0.08196 (1.0)   │   137.97 (1.0) 

benchmarks/drivers/test_build.py::test_build[rolling-severity=50]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.05971 (1.08)   │   69.22 (1.0) 
 (v1)         0.0551 (1.0)   │   69.22 (1.0) 

benchmarks/drivers/test_build.py::test_build[sos-n=1000]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.04543 (1.11)   │   402.33 (1.00) 
 (v1)        0.04107 (1.0)   │    402.30 (1.0) 

benchmarks/drivers/test_build.py::test_build[sos-n=10]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.04465 (1.10)   │   3.19 (1.19) 
 (v1)        0.04041 (1.0)   │    2.69 (1.0) 

benchmarks/drivers/test_build.py::test_build[sparse_network-n=10]
                  time (s)         peak (KiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.04933 (1.08)   │   29.00 (1.54) 
 (v1)        0.04579 (1.0)   │    18.84 (1.0) 

benchmarks/drivers/test_build.py::test_build[sparse_network-n=250]
                  time (s)         peak (MiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.05904 (1.11)   │   37.95 (1.43) 
 (v1)        0.05307 (1.0)   │    26.51 (1.0) 

benchmarks/drivers/test_build.py::test_build[storage-n=10]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)    0.09338 (1.0)   │    410.93 (1.0) 
 (v1)       0.09561 (1.02)   │   427.84 (1.04) 

benchmarks/drivers/test_build.py::test_build[storage-n=250]
                 time (s)         peak (MiB) 
 name                mean   │           mean 
─────────────────────────────────────────────
 (legacy)   0.09881 (1.0)   │     9.94 (1.0) 
 (v1)       0.1019 (1.03)   │   10.22 (1.03) 

📊 Interactive plots + CSV: download the semantics-report-v1-vs-legacy artifact from this run.

Report-only · not a gate · refreshed on every push · obsolete once legacy is dropped.

@codspeed

codspeed Bot commented Sep 15, 2026

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Merging this PR will degrade performance by 1.86%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 2 improved benchmarks
❌ 3 regressed benchmarks
✅ 176 untouched benchmarks
⏩ 181 skipped benchmarks1

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

Benchmark BASE HEAD Efficiency
test_to_lp[nodal_balance_sparse-severity=50] 2.8 MB 3.8 MB -27.31%
test_to_lp[qp-n=1000] 1.9 MB 2.6 MB -24.93%
test_to_lp[merge_balance-severity=0] 2.7 MB 3.3 MB -18.25%
test_to_lp[sparse_network-n=10] 1,338.9 KB 733.8 KB +82.47%
test_to_lp[expression_arithmetic-n=250] 46.7 MB 41.7 MB +11.84%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.


Comparing feat/956-compute-IIS-highs (2c22b9a) with master (718c0c1)

Open in CodSpeed

Footnotes

  1. 181 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports.

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Compute IIS with highs

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