Comment by shoo
8 days ago
what a great talk with many little highlights: code archaeology of a codebase passed between many teams & companies with the full revision history being lost somewhere along the way, detective work figuring out there had been an accidental regression in floating point precision when SIMD was enabled, obtaining higher performance by specialising/simplifying the 2d geometry algorithm to axis-aligned rectangular obstacles instead of the prior convex hull code, automatically fuzz-testing the proposed "obviously valid" algorithm by AI vs AI matches & using logging/invariants to identify and harvest nasty counterexamples, growing a unit test suite of 100 harvested nasty counterexamples while fixing the identified defects in the new algorithm, finally shipping it and receiving player feedback
My first job out of school was on one of the HD expansions at SkyBox Labs. It was mostly grunt feature work and desync fixes, but I remember that some of the handcoded ASM from the legacy pathfinding had been one-to-one translated to C++.
I always wondered if that contributed to the pathfinding regressions that were talked about online. Or, you learn about compiler-induced accidental UB in school, and part of me wondered if something was happening there.