[blegat]

Needs this one to be merged first, I'll rebase afterwards (so at the moment the diff contains both):

• Speed up CSC substitution decompression for stars #354

Add @inbounds to the CSC recovery loops and propagate it through the shared write helper with Base.@propagate_inbounds.

Fresh median timings for the same benchmark as #354:

Implementation	Recovery only	Full Hessian
Legacy MOI	98.07 μs	507.54 μs
SMC main	243.47 μs	666.90 μs
#354	137.98 μs	520.81 μs
This PR	88.59 μs	502.87 μs

On Julia 1.13.1 with Intel i7-12700K.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.38%. Comparing base (d88e142) to head (3cc18b5).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #355   +/-   ##
=======================================
  Coverage   99.37%   99.38%           
=======================================
  Files          22       22           
  Lines        2577     2592   +15     
=======================================
+ Hits         2561     2576   +15     
  Misses         16       16           

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[gdalle]

We've had this discussion with @amontoison in the past and I'm very uncomfortable adding @inbounds to a loop without previously checking that all indexing falls in the proper range. However I think this could be an opportunity to tighten our typing, and maybe put Vectors everywhere we can, to simplify this kind of verification (there are lots of places where AbstractVectors are accepted but really shouldn't be).

[blegat]

The tricky thing is to check that the CSC structure is satisfied. I tried adding an explicit loop and a first step but that was too expensive. What's best is to check bounds just for nzA and keep @inbounds for the others:

Pattern	Current	Checks bounds just for nzA	Verify nzA upfront
Chain, 65,536 vertices	186.4	188.9	277.6
Random, 4,096 vertices	124.0	123.8	173.8
Star, 65,536 vertices	60.6	60.8	112.