fix: avoid unnecessary recursion if not needed#3611
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ianna merged 11 commits intoscikit-hep:mainfrom Aug 26, 2025
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ikrommyd
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Aug 20, 2025
Co-authored-by: Iason Krommydas <iason.krom@gmail.com>
ikrommyd
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Fixes scikit-hep/coffea#1364 too |
This was referenced Aug 20, 2025
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Fixes scikit-hep/coffea#1389 |
ianna
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@pfackeldey - looks great! Thank you! Just a minor comment - I personally find the name of the flag confusing. Why not wrap_generator? Thanks
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@pfackeldey - Great! Thanks for addressing the comments!
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This PR avoids unnecessary recursion for VirtualArray transformations in case they are no-ops. Otherwise in rare cases we may descend down the call stack hell and discover circles of hell that even Dante Alighieri didn't know about...
There are no infinity recursions here; but because Python has a limit on the recursion depth we try to avoid them as much as possible. This wouldn't be an issue if Python would have had tail recursion optimization (but it doesn't). This issue is a language limitation...
To completely avoid recursion we could use a FIFO stack to track all operations and run them in order in the materialization, but that turns out to be harder to implement and will be very much unreadable, harder to maintain, and harder to reason about, which is why this PR doesn't do that now.
If anyone runs into this ever again (and that should be really weird edge cases), one can always increase Pythons recursion depth limit with
sys.setrecursionlimit(some_large_value). (Or we can revise the stack approach.)