ENH: delegate kron function.

[Enderdead]

This merge request introduces the kron delegate function (#100).

All supported backends already implement the kron function. However, I wasn’t able to add support for the sparse backend because it requires all input sparse matrices to have a fill_value equal to zero (not the case in the test) - likely to avoid generating a large dense matrix.

If you’d like to discuss potential support for kron in PyData Sparse, please let me know!

Feedback is welcome.

[Enderdead]

The test fails with the tests-numpy1 environment. I’m not able to reproduce this behavior on my machine (weird...).
The issue occurs when an input shape contains a zero.

I can update my delegation strategy to avoid delegating when the product of the shape elements equals zero (when using NumPy).

What do you think about this?

[lucascolley]

pixi run -e tests-numpy1 tests does reproduce the failures on my machine

[Enderdead]

@lucascolley I'm a bit confused, even with your command, I still can't reproduce the issue.

~/array-api-extra$ pixi run -e tests-numpy1 tests tests/test_funcs.py::TestKron::test_kron_shape[numpy-shape_a3-shape_b3]
✨ Pixi task (tests in tests-numpy1): pytest -v tests/test_funcs.py::TestKron::test_kron_shape[numpy-shape_a3-shape_b3]: (Run tests)                                     
========================================================================== test session starts ==========================================================================
platform linux -- Python 3.10.19, pytest-7.4.4, pluggy-1.4.0 -- /home/francois/array-api-extra/.pixi/envs/tests-numpy1/bin/python3.10
cachedir: .pytest_cache
hypothesis profile 'default'
rootdir: /home/francois/array-api-extra
configfile: pyproject.toml
plugins: typeguard-2.13.3, hypothesis-6.142.3, cov-7.0.0
collected 1 item                                                                                                                                                        

tests/test_funcs.py::TestKron::test_kron_shape[numpy-shape_a3-shape_b3] PASSED

[lucascolley]

what is your pixi list? For both me locally and CI, I see pytest is version 8.4.2, but your output shows pytest-7.4.4.

Maybe pixi run --locked makes a difference?

[Enderdead]

Here is the information you requested:

~/array-api-extra$ pixi reinstall -e tests-numpy1
✔ The tests-numpy1 environment has been re-installed.

~/array-api-extra$ pixi list
Package           Version     Build               Size       Kind   Source
_libgcc_mutex     0.1         conda_forge         2.5 KiB    conda  https://prefix.dev/conda-forge/
_openmp_mutex     4.5         2_gnu               23.1 KiB   conda  https://prefix.dev/conda-forge/
array-api-compat  1.12.0      pyhe01879c_0        44.7 KiB   conda  https://prefix.dev/conda-forge/
array_api_extra   0.9.1.dev0                                 pypi    (editable)
bzip2             1.0.8       hda65f42_8          254.2 KiB  conda  https://prefix.dev/conda-forge/
ca-certificates   2025.10.5   hbd8a1cb_0          152.3 KiB  conda  https://prefix.dev/conda-forge/
ld_impl_linux-64  2.44        ha97dd6f_2          729.6 KiB  conda  https://prefix.dev/conda-forge/
libexpat          2.7.1       hecca717_0          73.1 KiB   conda  https://prefix.dev/conda-forge/
libffi            3.5.2       h9ec8514_0          56.5 KiB   conda  https://prefix.dev/conda-forge/
libgcc            15.2.0      h767d61c_7          803.3 KiB  conda  https://prefix.dev/conda-forge/
libgomp           15.2.0      h767d61c_7          437.4 KiB  conda  https://prefix.dev/conda-forge/
liblzma           5.8.1       hb9d3cd8_2          110.2 KiB  conda  https://prefix.dev/conda-forge/
libmpdec          4.0.0       hb9d3cd8_0          89 KiB     conda  https://prefix.dev/conda-forge/
libsqlite         3.50.4      h0c1763c_0          910.7 KiB  conda  https://prefix.dev/conda-forge/
libuuid           2.41.2      he9a06e4_0          36.3 KiB   conda  https://prefix.dev/conda-forge/
libzlib           1.3.1       hb9d3cd8_2          59.5 KiB   conda  https://prefix.dev/conda-forge/
ncurses           6.5         h2d0b736_3          870.7 KiB  conda  https://prefix.dev/conda-forge/
openssl           3.5.4       h26f9b46_0          3 MiB      conda  https://prefix.dev/conda-forge/
python            3.13.9      hc97d973_101_cp313  35.5 MiB   conda  https://prefix.dev/conda-forge/
python_abi        3.13        8_cp313             6.8 KiB    conda  https://prefix.dev/conda-forge/
readline          8.2         h8c095d6_2          275.9 KiB  conda  https://prefix.dev/conda-forge/
tk                8.6.13      noxft_hd72426e_102  3.1 MiB    conda  https://prefix.dev/conda-forge/
tzdata            2025b       h78e105d_0          120.1 KiB  conda  https://prefix.dev/conda-forge/

~/array-api-extra$ pixi run --locked -e tests-numpy1 tests tests/test_funcs.py::TestKron::test_kron_shape[numpy-shape_a3-shape_b3]
✨ Pixi task (tests in tests-numpy1): pytest -v tests/test_funcs.py::TestKron::test_kron_shape[numpy-shape_a3-shape_b3]: (Run tests)                                     
========================================================================== test session starts ==========================================================================
platform linux -- Python 3.10.19, pytest-7.4.4, pluggy-1.4.0 -- /home/francois/array-api-extra/.pixi/envs/tests-numpy1/bin/python3.10
cachedir: .pytest_cache
hypothesis profile 'default'
rootdir: /home/francois/array-api-extra
configfile: pyproject.toml
plugins: typeguard-2.13.3, hypothesis-6.142.3, cov-7.0.0
collected 1 item                                                                                                                                                        

tests/test_funcs.py::TestKron::test_kron_shape[numpy-shape_a3-shape_b3] PASSED  

~/array-api-extra$ git status
Sur la branche kron_delegate
Votre branche est à jour avec 'origin/kron_delegate'.

rien à valider, la copie de travail est propre

[lucascolley]

ah sorry, I meant pixi list -e tests-numpy1

[Enderdead]

This is the pixi list. I just want to mention that I have the same behaviour with two different computer using kubuntu.

pixi list -e tests-numpy1
Environment: tests-numpy1
Package            Version     Build                 Size       Kind   Source
_libgcc_mutex      0.1         conda_forge           2.5 KiB    conda  https://prefix.dev/conda-forge/
_openmp_mutex      4.5         2_gnu                 23.1 KiB   conda  https://prefix.dev/conda-forge/
array-api-compat   1.12.0      pyhe01879c_0          44.7 KiB   conda  https://prefix.dev/conda-forge/
array-api-strict   2.4.1       pyhe01879c_0          61.1 KiB   conda  https://prefix.dev/conda-forge/
array_api_extra    0.9.1.dev0                                   pypi    (editable)
attrs              25.4.0      pyh71513ae_0          58.7 KiB   conda  https://prefix.dev/conda-forge/
bzip2              1.0.8       hda65f42_8            254.2 KiB  conda  https://prefix.dev/conda-forge/
ca-certificates    2025.10.5   hbd8a1cb_0            152.3 KiB  conda  https://prefix.dev/conda-forge/
click              8.3.0       pyh707e725_0          89.5 KiB   conda  https://prefix.dev/conda-forge/
colorama           0.4.6       pyhd8ed1ab_1          26.4 KiB   conda  https://prefix.dev/conda-forge/
coverage           7.11.0      py310h3406613_0       298.7 KiB  conda  https://prefix.dev/conda-forge/
exceptiongroup     1.3.0       pyhd8ed1ab_0          20.8 KiB   conda  https://prefix.dev/conda-forge/
hypothesis         6.142.3     pyha770c72_0          370.7 KiB  conda  https://prefix.dev/conda-forge/
iniconfig          2.3.0       pyhd8ed1ab_0          13.1 KiB   conda  https://prefix.dev/conda-forge/
ld_impl_linux-64   2.44        ha97dd6f_2            729.6 KiB  conda  https://prefix.dev/conda-forge/
libblas            3.9.0       37_h4a7cf45_openblas  17.1 KiB   conda  https://prefix.dev/conda-forge/
libcblas           3.9.0       37_h0358290_openblas  17.1 KiB   conda  https://prefix.dev/conda-forge/
libexpat           2.7.1       hecca717_0            73.1 KiB   conda  https://prefix.dev/conda-forge/
libffi             3.5.2       h9ec8514_0            56.5 KiB   conda  https://prefix.dev/conda-forge/
libgcc             15.2.0      h767d61c_7            803.3 KiB  conda  https://prefix.dev/conda-forge/
libgcc-ng          15.2.0      h69a702a_7            28.6 KiB   conda  https://prefix.dev/conda-forge/
libgfortran        15.2.0      h69a702a_7            28.6 KiB   conda  https://prefix.dev/conda-forge/
libgfortran5       15.2.0      hcd61629_7            1.5 MiB    conda  https://prefix.dev/conda-forge/
libgomp            15.2.0      h767d61c_7            437.4 KiB  conda  https://prefix.dev/conda-forge/
liblapack          3.9.0       37_h47877c9_openblas  17.1 KiB   conda  https://prefix.dev/conda-forge/
liblzma            5.8.1       hb9d3cd8_2            110.2 KiB  conda  https://prefix.dev/conda-forge/
libnsl             2.0.1       hb9d3cd8_1            32.9 KiB   conda  https://prefix.dev/conda-forge/
libopenblas        0.3.30      pthreads_h94d23a6_2   5.7 MiB    conda  https://prefix.dev/conda-forge/
libsqlite          3.50.4      h0c1763c_0            910.7 KiB  conda  https://prefix.dev/conda-forge/
libstdcxx          15.2.0      h8f9b012_7            3.7 MiB    conda  https://prefix.dev/conda-forge/
libstdcxx-ng       15.2.0      h4852527_7            28.7 KiB   conda  https://prefix.dev/conda-forge/
libuuid            2.41.2      he9a06e4_0            36.3 KiB   conda  https://prefix.dev/conda-forge/
libxcrypt          4.4.36      hd590300_1            98 KiB     conda  https://prefix.dev/conda-forge/
libzlib            1.3.1       hb9d3cd8_2            59.5 KiB   conda  https://prefix.dev/conda-forge/
ncurses            6.5         h2d0b736_3            870.7 KiB  conda  https://prefix.dev/conda-forge/
numpy              1.22.0      py310h454958d_1       19.4 MiB   conda  https://prefix.dev/conda-forge/
openssl            3.5.4       h26f9b46_0            3 MiB      conda  https://prefix.dev/conda-forge/
packaging          25.0        pyh29332c3_1          61 KiB     conda  https://prefix.dev/conda-forge/
pluggy             1.6.0       pyhd8ed1ab_0          23.7 KiB   conda  https://prefix.dev/conda-forge/
pygments           2.19.2      pyhd8ed1ab_0          868.4 KiB  conda  https://prefix.dev/conda-forge/
pytest             8.4.2       pyhd8ed1ab_0          270.2 KiB  conda  https://prefix.dev/conda-forge/
pytest-cov         7.0.0       pyhcf101f3_1          28.3 KiB   conda  https://prefix.dev/conda-forge/
python             3.10.19     h3c07f61_2_cpython    24.1 MiB   conda  https://prefix.dev/conda-forge/
python_abi         3.10        8_cp310               6.8 KiB    conda  https://prefix.dev/conda-forge/
readline           8.2         h8c095d6_2            275.9 KiB  conda  https://prefix.dev/conda-forge/
setuptools         80.9.0      pyhff2d567_0          731.2 KiB  conda  https://prefix.dev/conda-forge/
sortedcontainers   2.4.0       pyhd8ed1ab_1          28 KiB     conda  https://prefix.dev/conda-forge/
tk                 8.6.13      noxft_hd72426e_102    3.1 MiB    conda  https://prefix.dev/conda-forge/
tomli              2.3.0       pyhcf101f3_0          20.5 KiB   conda  https://prefix.dev/conda-forge/
typing_extensions  4.15.0      pyhcf101f3_0          50.5 KiB   conda  https://prefix.dev/conda-forge/
tzdata             2025b       h78e105d_0            120.1 KiB  conda  https://prefix.dev/conda-forge/

[lucascolley]

Do you have pytest installed globally? There is definitely a problem if pytest-7.4.4 is being used in your test runs, since your pixi list shows 8.4.2.