Using built-in Python hash for sorting goes against reproducibility

[wolfv]

Checklist

• [X] I added a descriptive title
• [X] I searched open reports and couldn't find a duplicate

What happened?

I've looked a bit into properly (byte-for-byte) reproducing the compressed artifacts in mamba and noticed that for the file-sorting the builtin hash function is used.

I think that's not a great choice because it makes the tarball less reproducible (e.g. from other programming languages, but also across different python versions). E.g. Python 4.x might decide to use a different string hashing algorithm.

I would propose to use some easy-to-implement string hashing algorithm instead (e.g. djb2: http://www.cse.yorku.ca/~oz/hash.html) or do away with it for sorting.

Conda Info

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Conda Config

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Conda list

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Additional Context

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[wolfv]

I tried to implement one of the simple hashing algorithms from the WWW but unfortunately it's a bit tricky in Python because it doesn't have integer overflow :) With numpy it's simple, but I don't think anyone would want numpy as dependency for that.

[wolfv]

Actually, this code seems to work:

# https://stackoverflow.com/a/14246007
def to_system_integer(value, bits, signed):
    base = 1 << bits
    value %= base
    return value - base if signed and value.bit_length() == bits else value

# from https://gist.github.com/amakukha/7854a3e910cb5866b53bf4b2af1af968
def hash_fnv1a_32(s):
    hash = 0x811c9dc5
    for x in s:
        hash = (ord(x) ^ hash) * 0x01000193
        hash = to_system_integer(hash, 64, 1)
    return hash

[mbargull]

Is this issue distinct from gh-181?

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