source: trunk/test/math/pi.cpp @ 2297

Last change on this file since 2297 was 2297, checked in by sam, 8 years ago

base: implement UNUSED() macro and put it here and there.

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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
7//   Public License, Version 2, as published by Sam Hocevar. See
8//   http://www.wtfpl.net/ 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    UNUSED(argc, argv);
27
28    printf("Pi: "); real::R_PI().print();
29    printf("e: "); real::R_E().print();
30    printf("ln(2): "); real::R_LN2().print();
31    printf("sqrt(2): "); real::R_SQRT2().print();
32    printf("sqrt(1/2): "); real::R_SQRT1_2().print();
33
34    /* Gauss-Legendre computation of Pi -- doesn't work well at all,
35     * probably because we use finite precision. */
36    real a = 1.0, b = sqrt((real)0.5), t = 0.25, p = 1.0;
37
38    for (int i = 0; i < 3; i++)
39    {
40        real a2 = (a + b) * (real)0.5;
41        real b2 = sqrt(a * b);
42        real tmp = a - a2;
43        real t2 = t - p * tmp * tmp;
44        real p2 = p + p;
45        a = a2; b = b2; t = t2; p = p2;
46    }
47
48    real sum = a + b;
49    sum = sum * sum / ((real)4 * t);
50    sum.print();
51
52    return EXIT_SUCCESS;
53}
54
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