Fast InvSqrt()

Fast InvSqrt()

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

Exey Panteleev | CC BY 2.0