Missing siphash24 support generates warnings in numba

[JC3]

See numba/numba#9994 for details.

Basically, when using numba with any of the builds here, numba always prints the following message on startup:

.../lib/python3.10/site-packages/numba/cpython/old_hashing.py:477: UserWarning: FNV hashing is not implemented in Numba. See PEP 456 https://www.python.org/dev/peps/pep-0456/ for rationale over not using FNV. Numba will continue to work, but hashes for built in types will be computed using siphash24. This will permit e.g. dictionaries to continue to behave as expected, however anything relying on the value of the hash opposed to hash as a derived property is likely to not work as expected.

I don't fully understand it but the explanation given in the above linked issue is:

this usually happens when Python has been built with FNV hashing instead of siphash24, which can happen due to configuration / setup errors at build time of the Python interpreter.

It was determined there that it's not an issue with numba but rather some missing option or configuration when creating the Python build.

Is it possible to update the builds to include siphash24 support? Apparently this is the default starting at 3.4 but the builds here don't have support for it, I'm not sure why.

A little research seems to suggest that calling configure with:

--with-hash-algorithm=siphash24

... will enable the algorithm, but again I'm not sure why the > 3.4 builds here don't seem to use it.

Sorry I don't know more about it.

[zanieb]

Hm, we do appear to include siphash24?

❯ uvx --managed-python python@3.10 -c "import sys; print(sys.hash_info.algorithm)"
siphash24

[zanieb]

That's macOS though, and from the linked thread it looks like you're on Ubuntu?

[zanieb]

❯ docker run -it astral/uv:bookworm-slim uvx --managed-python python@3.10 -c "import sys; print(sys.hash_info.algorithm)"
fnv

That does seem wrong indeed. I'll investigate.

[zanieb]

Hm, if I specify the architecture it's fine

❯ docker run --platform linux/amd64 -it astral/uv:bookworm-slim uvx --managed-python python@3.10 -c "import sys; print(sys.hash_info.algorithm)"
siphash24
❯ docker run --platform linux/aarch64 -it astral/uv:bookworm-slim uvx --managed-python python@3.10 -c "import sys; print(sys.hash_info.algorithm)"
siphash24

The first one downloads the artifact cpython-3.10.18-20250702-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz

[zanieb]

I think I may have been on an old image for the first example. Can you provide me with a reproduction?