r/ProgrammerHumor - Found this in Doom's code. is actually in the Quake III Arena code for calculating the inverse square root. Dating hacker girls. Follow the procedure to estimate the reciprocal of square root of given decimal the reciprocal of the square root For given c) Magic number (5FDF) Fast inverse square root, sometimes referred to as Fast InvSqrt or by the hexadecimal constant 0x5FDF, is an algorithm that estimates {\displaystyle {\frac {1}{\sqrt {x}}}}, the reciprocal of the square root of a bit floating-point number x. Found this in Doom's code. This is actually in the Quake III Arena code for calculating the inverse square root. float Q_rsqrt (float number) { long i; float x2, y; const float threehalfs = F; x2 = number * F; y = number; i = * (long *) &y; // evil floating point bit level hacking i = 0x5fdf - (i >> 1); // what the fuck? y = * (float *) &i; y = y * (threehalfs - (x2 * y * y)); // 1st iteration // y = y * . · The Fast Inverse Square Root function is a beautiful bit of code. I am both inspired and mesmerized by it. The world has Greg Walsh, the artist, and Estimated Reading Time: 6 mins. John Carmack has a special function in the Quake III source code which calculates the inverse square root of a float, 4x faster than regular (float)(/sqrt(x)), including a .
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