计算机算平方根用牛顿迭代。。。或者。。。下面这个fuck的方法
float InvSqrt(float x)
{
float xhalf = 0.5f*x;
int i = *(int*)&x; // get bits for floating VALUE
i = 0x5f375a86- (i>>1); // gives initial guess y0
x = *(float*)&i; // convert bits BACK to float
x = x*(1.5f-xhalf*x*x); // Newton step, repeating increases accuracy
return x;
}
参考：一个sqrt函数引发的血案
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InvSqrt.pdf
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