fix: sum() over a dimension crashes when a sibling dimension is empty by FBumann · Pull Request #907 · PyPSA/linopy

FBumann · 2026-08-27T07:59:21Z

Closes #906.

Note

The following content was generated by AI.

Dataset.stack reshapes with an inferred -1, which numpy cannot resolve once the array has zero elements — e.g. x.sum('line') when x also carries an empty cycle dimension. An empty expression has no terms, so it is now stacked onto a _term dimension of size 0, consistent with x.sum('cycle') and LinearExpression.from_constant(...) over the kept coordinates.

Three commits, best reviewed one by one:

strict-xfail regression test
pure refactor: extract _stack_into_term_dim from BaseExpression._sum (no behaviour change)
the edge case inside _stack_into_term_dim, un-xfail, release note

🤖 Generated with Claude Code

github-actions · 2026-08-27T08:02:40Z

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

Full table (time + peak, mean)

benchmarks/drivers/test_build.py::test_build[basic-n=10]
                  time (s)           peak (KiB) 
 name                 mean   │             mean 
────────────────────────────────────────────────
 (legacy)   0.06872 (1.09)   │      13.33 (1.0) 
 (v1)         0.0631 (1.0)   │   269.30 (20.20) 

benchmarks/drivers/test_build.py::test_build[basic-n=250]
                  time (s)         peak (MiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.07548 (1.11)   │   11.09 (1.00) 
 (v1)        0.06828 (1.0)   │    11.09 (1.0) 

benchmarks/drivers/test_build.py::test_build[cumsum-severity=0]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.02944 (1.11)   │   15.17 (1.0) 
 (v1)        0.02652 (1.0)   │   15.17 (1.0) 

benchmarks/drivers/test_build.py::test_build[cumsum-severity=100]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.04283 (1.11)   │   44.93 (1.0) 
 (v1)        0.03854 (1.0)   │   44.93 (1.0) 

benchmarks/drivers/test_build.py::test_build[cumsum-severity=50]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.03251 (1.09)   │   11.51 (1.0) 
 (v1)        0.02975 (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)   0.07877 (1.07)   │   24.23 (1.10) 
 (v1)        0.07377 (1.0)   │    22.05 (1.0) 

benchmarks/drivers/test_build.py::test_build[expression_arithmetic-n=250]
                  time (s)         peak (MiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.08844 (1.08)   │   15.64 (1.00) 
 (v1)         0.0822 (1.0)   │    15.64 (1.0) 

benchmarks/drivers/test_build.py::test_build[knapsack-n=10000]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.01895 (1.08)   │   752.15 (1.10) 
 (v1)        0.01759 (1.0)   │    685.11 (1.0) 

benchmarks/drivers/test_build.py::test_build[knapsack-n=100]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.01862 (1.08)   │   3.09 (1.34) 
 (v1)         0.0173 (1.0)   │    2.30 (1.0) 

benchmarks/drivers/test_build.py::test_build[kvl_cycles-severity=0]
                  time (s)          peak (MiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.05409 (1.26)   │   126.16 (1.44) 
 (v1)        0.04277 (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)   0.05324 (1.27)   │   126.16 (1.44) 
 (v1)        0.04188 (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)   0.05495 (1.31)   │   126.16 (1.44) 
 (v1)         0.0421 (1.0)   │     87.71 (1.0) 

benchmarks/drivers/test_build.py::test_build[masked-n=100]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.04099 (1.02)   │    714.28 (1.0) 
 (v1)        0.04022 (1.0)   │   785.32 (1.10) 

benchmarks/drivers/test_build.py::test_build[masked-n=10]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.04331 (1.21)   │   4.40 (1.34) 
 (v1)        0.03581 (1.0)   │    3.27 (1.0) 

benchmarks/drivers/test_build.py::test_build[merge_balance-severity=0]
                 time (s)          peak (KiB) 
 name                mean   │            mean 
──────────────────────────────────────────────
 (legacy)   0.3108 (1.05)   │   702.97 (1.10) 
 (v1)         0.296 (1.0)   │    639.22 (1.0) 

benchmarks/drivers/test_build.py::test_build[merge_balance-severity=100]
                 time (s)        peak (MiB) 
 name                mean   │          mean 
────────────────────────────────────────────
 (legacy)   0.3275 (1.06)   │   18.34 (1.0) 
 (v1)        0.3097 (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)   0.3235 (1.05)   │   9.54 (1.0) 
 (v1)        0.3093 (1.0)   │   9.54 (1.0) 

benchmarks/drivers/test_build.py::test_build[milp-n=10]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.05851 (1.10)   │   3.64 (1.14) 
 (v1)        0.05313 (1.0)   │    3.20 (1.0) 

benchmarks/drivers/test_build.py::test_build[milp-n=50]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.05871 (1.10)   │   216.15 (1.10) 
 (v1)        0.05323 (1.0)   │    195.76 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance-severity=0]
                  time (s)         peak (KiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.02887 (1.10)   │   935.30 (1.0) 
 (v1)         0.0262 (1.0)   │   935.30 (1.0) 

benchmarks/drivers/test_build.py::test_build[nodal_balance-severity=100]
                 time (s)       peak (MiB) 
 name                mean   │         mean 
───────────────────────────────────────────
 (legacy)   0.0299 (1.08)   │   9.66 (1.0) 
 (v1)       0.02779 (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)   0.03033 (1.12)   │   5.32 (1.0) 
 (v1)        0.02706 (1.0)   │   5.32 (1.0) 

benchmarks/drivers/test_build.py::test_build[piecewise-n=1000]
                 time (s)          peak (KiB) 
 name                mean   │            mean 
──────────────────────────────────────────────
 (legacy)   0.1427 (1.06)   │   891.72 (1.07) 
 (v1)        0.1343 (1.0)   │    836.28 (1.0) 

benchmarks/drivers/test_build.py::test_build[piecewise-n=10]
                 time (s)         peak (KiB) 
 name                mean   │           mean 
─────────────────────────────────────────────
 (legacy)   0.1407 (1.05)   │   11.02 (1.03) 
 (v1)        0.1339 (1.0)   │    10.67 (1.0) 

benchmarks/drivers/test_build.py::test_build[qp-n=1000]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.03997 (1.08)   │   147.66 (1.06) 
 (v1)         0.0369 (1.0)   │    139.84 (1.0) 

benchmarks/drivers/test_build.py::test_build[qp-n=10]
                  time (s)        peak (KiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.03934 (1.07)   │   2.57 (1.09) 
 (v1)        0.03673 (1.0)   │    2.35 (1.0) 

benchmarks/drivers/test_build.py::test_build[rolling-severity=0]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.02989 (1.10)   │   696.72 (1.14) 
 (v1)        0.02723 (1.0)   │    611.13 (1.0) 

benchmarks/drivers/test_build.py::test_build[rolling-severity=100]
                  time (s)         peak (MiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.07296 (1.10)   │   137.97 (1.0) 
 (v1)        0.06638 (1.0)   │   137.97 (1.0) 

benchmarks/drivers/test_build.py::test_build[rolling-severity=50]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)   0.04776 (1.06)   │   69.22 (1.0) 
 (v1)        0.04489 (1.0)   │   69.22 (1.0) 

benchmarks/drivers/test_build.py::test_build[sos-n=1000]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)   0.03388 (1.14)   │   377.39 (1.04) 
 (v1)         0.0297 (1.0)   │    363.14 (1.0) 

benchmarks/drivers/test_build.py::test_build[sos-n=10]
                 time (s)        peak (KiB) 
 name                mean   │          mean 
────────────────────────────────────────────
 (legacy)   0.0334 (1.14)   │   3.10 (1.41) 
 (v1)       0.02942 (1.0)   │    2.20 (1.0) 

benchmarks/drivers/test_build.py::test_build[sparse_network-n=10]
                  time (s)         peak (KiB) 
 name                 mean   │           mean 
──────────────────────────────────────────────
 (legacy)   0.03867 (1.10)   │   28.94 (1.61) 
 (v1)        0.03513 (1.0)   │    17.97 (1.0) 

benchmarks/drivers/test_build.py::test_build[sparse_network-n=250]
                 time (s)         peak (MiB) 
 name                mean   │           mean 
─────────────────────────────────────────────
 (legacy)   0.0498 (1.14)   │   37.95 (1.43) 
 (v1)       0.04383 (1.0)   │    26.51 (1.0) 

benchmarks/drivers/test_build.py::test_build[storage-n=10]
                  time (s)          peak (KiB) 
 name                 mean   │            mean 
───────────────────────────────────────────────
 (legacy)    0.07682 (1.0)   │    397.39 (1.0) 
 (v1)       0.07753 (1.01)   │   414.56 (1.04) 

benchmarks/drivers/test_build.py::test_build[storage-n=250]
                  time (s)        peak (MiB) 
 name                 mean   │          mean 
─────────────────────────────────────────────
 (legacy)    0.08181 (1.0)   │    9.62 (1.0) 
 (v1)       0.08536 (1.04)   │   9.90 (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-hq · 2026-08-27T08:03:12Z

Merging this PR will regress 4 benchmarks

⚠️

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

⚡ 5 improved benchmarks
❌ 4 regressed benchmarks
✅ 166 untouched benchmarks
⏩ 175 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Memory	`test_to_lp[milp-n=50]`	2 MB	2.6 MB	-23.36%
❌	Memory	`test_to_lp[nodal_balance-severity=50]`	2.8 MB	3.3 MB	-15.08%
❌	Memory	`test_to_lp[rolling-severity=0]`	2.7 MB	3.1 MB	-12.55%
❌	Memory	`test_to_lp[nodal_balance-severity=0]`	3.3 MB	3.7 MB	-10.29%
⚡	Memory	`test_to_lp[knapsack-n=10000]`	2.8 MB	2.2 MB	+26.3%
⚡	Memory	`test_to_lp[cumsum-severity=100]`	208.7 MB	172 MB	+21.37%
⚡	Memory	`test_to_lp[storage-n=250]`	35.4 MB	29.6 MB	+19.68%
⚡	Memory	`test_to_lp[rolling-severity=50]`	429.7 MB	367.7 MB	+16.88%
⚡	Memory	`test_to_lp[storage-n=10]`	2.9 MB	2.6 MB	+10.79%

Tip

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

_{Comparing fix/sum-empty-sibling-dim (3f2c50a) with master (09c34dd)²}

175 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. ↩
No successful run was found on master (570ff2e) during the generation of this report, so 09c34dd was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

FBumann added the bug Something isn't working label Aug 27, 2026

test: xfail sum() over a dim when a sibling dim is empty (#906)

8e74964

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

FBumann force-pushed the fix/sum-empty-sibling-dim branch from f64b8a0 to f90d3d9 Compare August 27, 2026 08:49

refactor: extract _stack_into_term_dim from BaseExpression._sum

a990667

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

FBumann force-pushed the fix/sum-empty-sibling-dim branch from f90d3d9 to ffc6bb5 Compare August 27, 2026 08:53

fix: sum() over a dim when a sibling dim is empty (#906)

653160d

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

FBumann force-pushed the fix/sum-empty-sibling-dim branch from ffc6bb5 to 653160d Compare August 27, 2026 09:13

FBumann requested a review from FabianHofmann August 27, 2026 09:14

This was referenced Aug 27, 2026

refactor(linopy): a grouped sum's empty group is filled by the caller rather than by a hand-written storage row fluxopt/lpspec#1375

Merged

the linopy lane builds through linopy's public surface, not its storage layout fluxopt/lpspec#1367

Open

Merge branch 'master' into fix/sum-empty-sibling-dim

3f2c50a

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fix: sum() over a dimension crashes when a sibling dimension is empty - #907

fix: sum() over a dimension crashes when a sibling dimension is empty#907
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Build cost — v1 vs legacy

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Merging this PR will regress 4 benchmarks

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