fork(1) download
copy 
  1. #include <iostream>
  2. #include <chrono>
  3. #include <cmath>
  4.  
  5. using namespace std;
  6.  
  7. #define ITERATIONS 5000
  8.  
  9. static double	_t;
  10. static double	_i;
  11. static double	_f;
  12.  
  13. inline double my_fmod( double y, double x ) {
  14. 	double r;
  15. 	__asm__ __volatile__ (
  16. 		"0:				\n"
  17. 		"fprem			\n"
  18. 		"fstsw	%%ax	\n"
  19. 		"sahf			\n"
  20. 		"jp		0b		\n"
  21. 		: "=t" (r) : "0" (y), "u" (x) : "ax" );
  22. 	return r;
  23. }
  24.  
  25. inline double my_modf( double x, double *iptr ) {
  26. 	double fmod_result = my_fmod( x, 1 );
  27. 	*iptr = x - fmod_result;
  28. 	return fmod_result;
  29. }
  30.  
  31. inline double my_floor( double x ) {
  32. 	double r;
  33. 	__asm__ __volatile__ (
  34. 		"mov	$0x04, %%ah		\n"
  35. 		"xor	%%ecx, %%ecx	\n"
  36. 		"mov	%%ah, %%ch		\n"
  37. 		"push	%%eax			\n"
  38. 		"fstcw	(%%esp)			\n"
  39. 		"mov	(%%esp), %%ax	\n"
  40. 		"and	$0x03, %%ah		\n"
  41. 		"or		%%ecx, %%eax	\n"
  42. 		"mov	%%ax, 2(%%esp)	\n"
  43. 		"fldcw	2(%%esp)		\n"
  44. 		"frndint				\n"
  45. 		"fldcw	(%%esp)			\n"
  46. 		"pop	%%eax			\n"
  47. 		: "=t" (r) : "0" (x) : "ax" );
  48. 	return r;
  49. }
  50.  
  51.  
  52. void native_floor() {
  53. 	_i = floor( _t );
  54. 	_f = (_t - _i) * 0x100000000;
  55. }
  56.  
  57. void custom_floor() {
  58. 	_i = my_floor( _t );
  59. 	_f = (_t - _i) * 0x100000000;
  60. }
  61.  
  62. void native_modf() {
  63. 	_f = modf( _t, &_i );
  64. }
  65.  
  66. void custom_modf() {
  67. 	_f = my_modf( _t, &_i );
  68. }
  69.  
  70. #define MEASURE( func )										\
  71. 	a = chrono::system_clock::now();						\
  72. 	for ( unsigned i = 0; i < ITERATIONS; i++ ) {			\
  73. 		for ( unsigned j = 0; j < ITERATIONS; j++ ) {		\
  74. 			func();											\
  75. 		}													\
  76. 	}														\
  77. 	b = chrono::system_clock::now();						\
  78. 	cout << #func << " : " << chrono::duration_cast< chrono::milliseconds >( b - a ).count() << " ms." << endl;
  79.  
  80.  
  81. int main()
  82. {
  83. 	chrono::system_clock::time_point a, b;
  84.  
  85. 	_t = (double)(rand() % RAND_MAX) / RAND_MAX * 1000;
  86.  
  87. 	MEASURE( native_floor );
  88. 	MEASURE( custom_floor );
  89. 	MEASURE( native_modf );
  90. 	MEASURE( custom_modf );
  91.  
  92. 	return 0;
  93. }
Success #stdin #stdout 2.05s 3340KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
native_floor : 667 ms.
custom_floor : 548 ms.
native_modf : 596 ms.
custom_modf : 241 ms.
https://ideone.com/lUBX1A
Small benchmark for standart floor and modf functions.
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!