快速平方根倒数算法

[未完成]

#include <iostream>
using namespace std;

/*
** float q_rsqrt( float number )
*/
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;
}

int main() {
    float temp;
    cin >> temp;
    cout << Q_rsqrt(temp) << endl;

    system("pause");
    return 0;
}