A detailed technical walkthrough of profiling and optimizing a headless Unity simulation from 21 to 25 FPS — covering NVENC GPU encoding, batch camera rendering, GPU instancing, static batching, and the failed URP migration. Every measurement, every dead end, every lesson.
How a simple erase-remove in every add_timer() call turned entity registration into a quadratic bottleneck — and the 71x speedup from moving cleanup to the right place.
Eigen’s blocked Householder path only existed for left-side application. I added the right-side equivalent, upgrading M*Q from O(n) rank-1 updates to cache-friendly blocked matrix multiplies.
A performance optimization in Eigen’s fill path assumed all scalar types are equal. GCC’s libstdc++ disagreed — and AutoDiffScalar paid the price.