牛顿迭代法-续
[cpp]
程序代码：
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
#ifndef Q3_VM #
ifdef __linux__ assert( !isnan(y) ); // bk010122 - FPE?
#endif
#endif return y;
}
一发不可收拾，请问有人可以说说里面的那句迷之代码的原理？
i = 0x5f3759df - ( i >> 1 );
引用自：
http://blog.
[此贴子已经被作者于2017-1-21 14:30编辑过]
