Reference Issues/PRs

Fix #19602.

What does this implement/fix? Explain your changes.

This makes it possible to save a decision tree pickle on a 64bit machine and load it on a 32bit machine (as well as the other way around although this is probably not that useful in practice).

The test uses a similar approach as #21539: it checks that a pickle containing arrays of a different bitness (e.g. 64bit arrays on a 32bit machine) can be loaded fine. This is not exactly what we want to test, i.e. generating a pickle on 64bit machine and load it on a 32 bit machine but is close enough.

If we want, we could have an additional test that is exactly the use case we are aiming to support. We can generate pickle bytes on a 64 bit machine (we can put a comment indicating how to generate it if we need to regenerate it) and load it on the 32 bit CI.

Any other comments?

#21539 should be merged first, putting this one in draft for now.

• once Test decision tree pickle for different endianness #21539 is merged, I think that the endianness test should pass with joblib < 1.1 so I can remove pytest.mark.skipif

Testing a similar thing for more/other estimators is left for a future PR.