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  1. #include <stdio.h>
  2.  
  3. double fisr(double number);
  4.  
  5. int main(void) {
  6. 	double a = 2;
  7. 	//scanf("%lf", &a);
  8. 	printf("%lfn", fisr(a));
  9.  
  10. 	return 0;
  11. }
  12.  
  13. double fisr(double number) {
  14. 	long i;
  15. 	float x2, y;
  16. 	const float threehalfs = 1.5F;
  17.  
  18. 	x2 = number * 0.5F;
  19. 	y  = number;
  20. 	i  = * ( long * ) &y;                       // evil floating point bit level hacking
  21. 	i  = 0x5f3759df - ( i >> 1 );               // what the fuck? 
  22. 	y  = * ( float * ) &i;
  23. 	y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
  24. //	y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed
  25.  
  26. 	return y;
  27. }
Success #stdin #stdout 0s 9424KB
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https://ideone.com/cx0Zx3
language:
C (gcc 8.3)
created:
5 years ago
visibility:
public

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