Skill: performance-optimization

Measure First — the gate every optimization passes through

Profile before optimizing — intuition about hot spots is measurably wrong more often than right:

• Correctness before speed -- make it work, then make it fast
• <4% of code causes >50% of runtime (Knuth 1971) -- find the hot spot before touching anything
• >50% of optimizations produce negligible or negative results -- measurement prevents wasted effort

Optimization proceeds only from a measurement — unmeasured "optimizations" are edits with a coin-flip chance of helping.

Scope Limitations

This skill covers single-threaded, single-process code tuning for general-purpose computing.