0x5f3759df and the fast inverse square root (2012)(h14s.p5r.org)

    fn fast_inv_sqrt(x: f32) -> f32 {
        let f: f32 = unsafe {
            let i: i32 = std::mem::transmute(x);
            std::mem::transmute(0x5f3759df - (i >> 1))
        };
        f * (1.5 - 0.5 * x * f * f)
    }

    println!("{}", fast_inv_sqrt(1.0));
      //=> 0.998307
    println!("{}", fast_inv_sqrt(255.0));
      //=> 0.062517