sqrt.c

#include <stdio.h>

float InvSqrt(float x)
{
    float xhalf = 0.5f * x;
    int i = *(int*)&x;
    i = 0x5f375a86 - (i>>1);
    printf("%d", i);
    x = *(float*)&i;
    printf("%f", x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    x = x*(1.5f - xhalf*x*x);
    return x;
}


int main(int argc, char *argv[])
{
    printf("%f\n", 1.0f / InvSqrt(15.3f));
    return 0;
}