Last change
on this file since 1893 was
1893,
checked in by sam, 7 years ago

math: refactor real number constant declarations so that they are only
computed on demand with static initialisation.


Property svn:keywords set to
Id

File size:
1.3 KB

Line  

1  // 

2  // Lol Engine  Sample math program: compute Pi 

3  // 

4  // Copyright: (c) 20052011 Sam Hocevar <sam@hocevar.net> 

5  // This program is free software; you can redistribute it and/or 

6  // modify it under the terms of the Do What The Fuck You Want To 

7  // Public License, Version 2, as published by Sam Hocevar. See 

8  // http://sam.zoy.org/projects/COPYING.WTFPL for more details. 

9  // 

10  

11  #if defined HAVE_CONFIG_H 

12  # include "config.h" 

13  #endif 

14  

15  #include <cstdio> 

16  

17  #include "core.h" 

18  

19  using std::printf; 

20  using std::sqrt; 

21  

22  using lol::real; 

23  

24  int main(int argc, char **argv) 

25  { 

26  printf("Pi: "); real::R_PI().print(); 

27  printf("e: "); real::R_E().print(); 

28  printf("ln(2): "); real::R_LN2().print(); 

29  printf("sqrt(2): "); real::R_SQRT2().print(); 

30  printf("sqrt(1/2): "); real::R_SQRT1_2().print(); 

31  

32  /* GaussLegendre computation of Pi  doesn't work well at all, 

33  * probably because we use finite precision. */ 

34  real a = 1.0, b = sqrt((real)0.5), t = 0.25, p = 1.0; 

35  

36  for (int i = 0; i < 3; i++) 

37  { 

38  real a2 = (a + b) * (real)0.5; 

39  real b2 = sqrt(a * b); 

40  real tmp = a  a2; 

41  real t2 = t  p * tmp * tmp; 

42  real p2 = p + p; 

43  a = a2; b = b2; t = t2; p = p2; 

44  } 

45  

46  real sum = a + b; 

47  sum = sum * sum / ((real)4 * t); 

48  sum.print(); 

49  

50  return EXIT_SUCCESS; 

51  } 

52  

Note: See
TracBrowser
for help on using the repository browser.