Specialize adapt_structure for small tuples

[charleskawczynski]

Closes #79.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 92.85%. Comparing base (9c1b146) to head (5e85c7c).

Files	Patch %	Lines
src/base.jl	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
- Coverage   93.65%   92.85%   -0.80%     
==========================================
  Files           6        6              
  Lines          63       70       +7     
==========================================
+ Hits           59       65       +6     
- Misses          4        5       +1     

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[maleadt]

Can't you do this with a simple if, assuming it would get compiled away, instead of inserting many methods?

This also reminds me of JuliaLang/julia#53665.

[charleskawczynski]

I was going to suggest that we could use an if-statement, is that your preference?

[maleadt]

Yes, you're now putting additional pressure on the dispatch system where the compiler should be able to handle this just fine.

[charleskawczynski]

Alright, I've updated the PR. This passes inference for me in the #79 example. Does 20 qualify as "small", @maleadt?

[charleskawczynski]

bump 🙂

[maleadt]

I don't like that we don't have a test for this, but OK I guess.

Seeing how you went with the if approach, I take it using afold (which handles this in Base, https://github.com/JuliaLang/julia/blob/bc7ba3d5c8b2dab1c0e19537739b67c2da902d11/base/operators.jl#L579-L625) didn't solve the allocations?

[charleskawczynski]

I don't like that we don't have a test for this, but OK I guess.

Seeing how you went with the if approach, I take it using afold (which handles this in Base, https://github.com/JuliaLang/julia/blob/bc7ba3d5c8b2dab1c0e19537739b67c2da902d11/base/operators.jl#L579-L625) didn't solve the allocations?

Thank you for merging!

Yeah, I agree about the tests. I did try to write a simple reproducer, but I wasn't able to recreate the failure. I'm not sure what ingredients are needed. I'll take another look to see if I can cook something up.

I tend to try to avoid using Julia internals, but I can check to see if afold works if you prefer that over the existing solution.

[maleadt]

I tend to try to avoid using Julia internals

Yeah, that's fair.

[charleskawczynski]

I've updated, and I'll try to continue updating/simplifying, the reproducer in #79. It's drastically simpler now, although there's still a lot more to go.

[charleskawczynski]

Thanks again for fixing this! This fixed 955 inference failures per timestep 😬 found by JET! 🚀