2 releases
0.1.1 | Jun 27, 2022 |
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0.1.0 | Jun 27, 2022 |
#1040 in Math
4KB
This is a implementation of the fast inverse square root function from quake 3.
It can be up to three times as fast as using the .sqrt()
method on a float32
Keep in mind that fast inverse square root is only accurate within a one percent margin of error
Here's the original implementation:
float Q_rsqrt( float number )
{
long i;
float x2, y;
const float threehalfs = 1.5F;
x2 = number * 0.5F;
y = number;
i = * ( long * ) &y; // evil floating point bit level hacking
i = 0x5f3759df - ( i >> 1 ); // what the fuck?
y = * ( float * ) &i;
y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration
// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed
return y;
}