关于平方根的计算,在linux内核中也有实现,就像math.h数学库里的sqrt这个函数一样。
平方根的公式定义:
假设一个非负数x的平方等于a。即
。
,那么这个非负数x叫做a的算术平方根。a的算术平方根记为
,读作“根号a”,a叫做被开方数(radicand)。求一个非负数a的平方根的运算叫做开平方。结论:被开方数越大,相应的算术平方根也越大(对全部正数都成立)。
![](http://a.hiphotos.baidu.com/baike/s%3D43/sign=50bb6fea0bf79052eb1f463d0df3ed9a/e1fe9925bc315c6044b777168fb1cb134954772c.jpg)
![](http://g.hiphotos.baidu.com/baike/s%3D45/sign=684da21db11c8701d2b6b3e3267fb7b9/5882b2b7d0a20cf47793e22674094b36adaf99c3.jpg)
![](http://b.hiphotos.baidu.com/baike/s%3D20/sign=3924b9b4be315c6047956cef8cb10f1a/aec379310a55b319321e97d441a98226cefc17af.jpg)
哈哈。小学生都懂。不解释不解释,直接来看代码:![大笑](http://static.blog.csdn.net/xheditor/xheditor_emot/default/laugh.gif)
![大笑](http://static.blog.csdn.net/xheditor/xheditor_emot/default/laugh.gif)
一样的。从内核里把代码取出来:
#include <stdio.h> #ifdef CONFIG_64BIT #define BITS_PER_LONG 64 #else #define BITS_PER_LONG 32 #endif /** * int_sqrt - rough approximation to sqrt * @x: integer of which to calculate the sqrt * * A very rough approximation to the sqrt() function. */ unsigned long int_sqrt(unsigned long x) { unsigned long op, res, one; op = x; res = 0; one = 1UL << (BITS_PER_LONG - 2); while (one > op) one >>= 2; while (one != 0) { if (op >= res + one) { op = op - (res + one); res = res + 2 * one; } res /= 2; one /= 4; } return res; } int main(void) { printf("%d ",int_sqrt(16)) ; return 0 ; }执行结果: