Fix progressbar bug for parallel SMC sampling

[jucor]

See discussion in #7078 (comment)

Description

As discussed in #7078, running parallel SMC sampling (cores > 1) from within a notebook crashes. The package progressbar throws an error because it is not finding HTML. That error only occurs when running multiple chains in parallel from within a jupyter notebook.

This is because the progressbar module conditionally imports HTML at import time if it detects that it is imported from a notebook process, which is the case when the progress bar is created before the multi-chain forking. When the subprocess corresponding to one chain then tries to update the progress bar, it does so from a process that was not a notebook process when it imported the progressbar module after forking, and thus HTML is not imported.

The simplest fix, that I have implemented, is to force the use of a non-HTML (aka console, i.e. text mode) progressbar when sample_smc is running parallel chains. 2-lines fix :)

While I discovered this bug while investing another behaviour in #7078, it is also the underlying issue to #5855 and #5980, which were closed but not really fixed.

I wish I could add a unit test, but not easy way as this behavior occurs only when pymc.smc_sample is called from within a jupyter notebook. A test would therefore have to run a jupyter server then run a notebook then catch the error.

No documentation update needed.

Related Issue

• Closes NameError: name 'HTML' is not defined #5855
• Closes name 'HTML' is not define with pm.sample_smc() #5980
• Related to BUG: as_op not pickled, making parallel SMC crash #7078

Checklist

• Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Type of change

• New feature / enhancement
• Bug fix
• Documentation
• Maintenance
• Other (please specify):

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📚 Documentation preview 📚: https://pymc--7079.org.readthedocs.build/en/7079/

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (118be0f) 92.21% compared to head (843ad7c) 92.21%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7079   +/-   ##
=======================================
  Coverage   92.21%   92.21%           
=======================================
  Files         101      101           
  Lines       16912    16913    +1     
=======================================
+ Hits        15595    15596    +1     
  Misses       1317     1317           

Files	Coverage Δ
pymc/smc/sampling.py	99.30% <100.00%> (+<0.01%)	⬆️

[jucor]

👋 Hi @aloctavodia, Sorry to bother you, would you have any time for reviewing this one-line change, please?
Thanks @twiecki !

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]
Congrats on merging your first pull request! 🎉 We here at PyMC are proud of you! 💖 Thank you so much for your contribution 🎁

[twiecki]

👋 Hi @aloctavodia, Sorry to bother you, would you have any time for reviewing this one-line change, please?
Thanks @twiecki !

Thanks for the contribution!