fast inverse square root (approximate)
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#include <stdio.h>
float Q_sqrt(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;
}
// test
int main(void) {
printf("%f",Q_sqrt(226.0f)); // real answer: ~0.06651901...
return 0;
}
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