Fast InvSqrt()

1 photo · 👩🏼 Vlada Votrina

Fast Inverse Square Root is an algorithm(based on magic number 0x5f3759df) that quickly(3–4 times faster, but loss of accuracy <~1%) estimates the inverse of the square root of a float variable. Method was developed by Cleve Moler and Gregory Walsh in 1986. This optimization was used in Interstate '76 and Quake 3 Arena video games in late 90s