- 论坛徽章:
- 8
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- 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;
- }
复制代码 1、what the fuck那行,那个magic number是怎么得来的?如果以后遇到了类似问题,我该怎么自己找出这类数字?
2、为何2nd iteration can be removed? |
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