Fix 2114

[jajhall]

Highs::getCols and (Highs::getRows) now should run in linear time if the matrix is stored column-wise (row-wise). Achieved without duplicated code by creating row/column agnostic getSubVectors and getSubVectorsTranspose in HighsLpUtils

[galabovaa]

Great! The failing workflows are fixed by #2112, please review it :)

[jajhall]

This was meant to be a draft PR

[odow]

This branch is faster, but I still get (using my benchmark from #2114):

Running HiGHS 1.9.0 (git hash: 8787bebac): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 1000  0.02s user 0.01s system 89% cpu 0.026 total
Running HiGHS 1.9.0 (git hash: 8787bebac): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 2000  0.03s user 0.01s system 94% cpu 0.035 total
Running HiGHS 1.9.0 (git hash: 8787bebac): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 4000  0.08s user 0.01s system 97% cpu 0.094 total
Running HiGHS 1.9.0 (git hash: 8787bebac): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 8000  0.30s user 0.02s system 98% cpu 0.321 total
Running HiGHS 1.9.0 (git hash: 8787bebac): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 16000  1.03s user 0.04s system 99% cpu 1.068 total
Running HiGHS 1.9.0 (git hash: 8787bebac): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 32000  4.66s user 0.07s system 99% cpu 4.738 total

Ideally, if the matrix is stored in row-major, querying the row function should be O(1)? I want this benchmark to have O(N) scaling.

[odow]

Muuuuuch better! This looks great.

Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 1000  0.01s user 0.01s system 82% cpu 0.023 total
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 2000  0.01s user 0.00s system 91% cpu 0.018 total
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 4000  0.02s user 0.00s system 93% cpu 0.024 total
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 8000  0.03s user 0.01s system 95% cpu 0.037 total
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 16000  0.06s user 0.01s system 95% cpu 0.066 total
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 32000  0.11s user 0.01s system 96% cpu 0.120 total
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 64000  0.21s user 0.01s system 98% cpu 0.224 total
(base) oscar@MacBookPro HiGHS % time ./examples/main 128000
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 128000  0.42s user 0.02s system 98% cpu 0.444 total
(base) oscar@MacBookPro HiGHS % time ./examples/main 256000
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 256000  0.88s user 0.04s system 98% cpu 0.931 total
(base) oscar@MacBookPro HiGHS % time ./examples/main 512000
Running HiGHS 1.9.0 (git hash: a5f01ca95): Copyright (c) 2025 HiGHS under MIT licence terms
./examples/main 512000  1.62s user 0.07s system 98% cpu 1.704 total