GPL, written by Greg Walsh
0
fast-inverse-square-root.c
1float Q_rsqrt( float number )
2{
3 long i;
4 float x2, y;
5 const float threehalfs = 1.5F;
6
7 x2 = number * 0.5F;
8 y = number;
9 i = * ( long * ) &y; // evil floating point bit level hacking
10 i = 0x5f3759df - ( i >> 1 ); // what the fuck?
11 y = * ( float * ) &i;
12 y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration
13// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed
14
15 return y;
16}