# source:trunk/test/math/pi.cpp@1893Tweet

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) 2005-2011 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
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
19using std::printf;
20using std::sqrt;
21
22using lol::real;
23
24int 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    /* Gauss-Legendre 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
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