Create and run benchmarks

I need to measure whether the latest refactor improved performance for the collision system. Build a small harness that runs the new and old implementations back-to-back on the same inputs and reports mean, median and 95th percentile times in milliseconds over 10,000 iterations. Use the existing test scene from Tests/Scenes/arena.csv, pin the thread to one core, and seed the RNG with 42. Produce a CSV with columns: implementation,iteration,ms. Ladder L1

Before I hand this benchmark to QA, make the results easy to interpret: put the percent difference from baseline and a clear statement about statistical significance up top, highlight any input sizes where the new code is slower, and add a short note on whether the harness pins threads and warms caches. Keep the harness runnable as a single .cpp with command-line flags for iterations and input file. Ladder L2

I ran the benchmark against the arena scene with 10,000 iterations and the new refactor shows a 7% improvement in mean time but the 95th percentile is 55% worse. I fear the change introduces occasional expensive branches under specific object layouts. I cannot easily inspect runtime object geometry in the harness. What is the likely cause and the best next experiment to narrow it down? Ladder L5

Across multiple refactors I keep shipping faster averages but with unpredictable worst-case spikes that users complain about. Where am I going wrong in how I design microbenchmarks and CI signals, and what habit should I change to avoid these tail regressions becoming production incidents? Suggest one concrete change to the harness, one CI policy change, and one simple developer habit. Ladder L6