0x5F3759DF
Fast inverse square root constant
The bit-level constant from Quake III Arena's Q_rsqrt: subtracting (i >> 1) from it gives a remarkably good first guess at 1/sqrt(x). Famously annotated "what the f...?" in the original source.
Similar magic numbers
| value | name | category |
|---|---|---|
| 5F 27 A8 89 | Jar archive | file-signature |
| 5F 43 41 53 45 5F | EnCase case file | file-signature |