【黑科技】快速开方

版权声明：转载请声明出处，谢谢配合。 https://blog.csdn.net/zxyoi_dreamer/article/details/82148356

一个很玄学的代码片。。
实测比cmath里面的sqrt要快

float qsqrt(float x) { 
    if(x == 0) return 0; 
    float result = x; 
    float xhalf = 0.5f*result; 
    int i = *(int*)&result; 
    i = 0x5f375a86- (i>>1); 
    result = *(float*)&i; 
    result = result*(1.5f-xhalf*result*result); 
    result = result*(1.5f-xhalf*result*result); 
    return 1.0f/result; 
}