Fast Inverse Square Root

Fast inverse square root explained

    float InvSqrt(float x){
        float xhalf = 0.5f * x;
        int i = *(int*)&x;            // store floating-point bits in integer
        i = 0x5f3759df - (i >> 1);    // initial guess for Newton's method
        x = *(float*)&i;              // convert new bits into float
        x = x*(1.5f - xhalf*x*x);     // One round of Newton's method
        return x;
    }

Source: betterexplained.com

Fast Inverse Square Root

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;
}

Source: en.wikipedia.org

Similar codes

0 vote289 views1 answer
Static cast char c++
C++
20 votes282 views5 answers
Char * to string c++
C++
1 vote307 views4 answers
Sum vector c++
C++
-1 vote318 views2 answers
Inline function in cpp
C++
0 vote326 views1 answer
How to set a variable to infinity in c++
C++
0 vote279 views1 answer
Clear qlayout
C++
1 vote319 views1 answer
Joining two vectors in c++
C++
5 votes286 views2 answers
C++ return multiple values
C++
35 votes301 views6 answers
Ellipsis
C++
0 vote314 views1 answer
Skip headers while reading text
C++