f.cpp revision d312b224b6759fd9b206d4c19450f6a4dfe53311 
1/**************************************************************************
2 *
3 * (C) Copyright VMware, Inc 2010.
4 * (C) Copyright John Maddock 2006.
5 * Use, modification and distribution are subject to the
6 * Boost Software License, Version 1.0. (See accompanying file
7 * LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8 *
9 **************************************************************************/
10
11
12/*
13 * This file allows to compute the minimax polynomial coefficients we use
14 * for fast exp2/log2.
15 *
16 * How to use this source:
17 *
18 * - Download and build the NTL library from
19 *   http://shoup.net/ntl/download.html , or install libntl-dev package if on
20 *   Debian.
21 *
22 * - Download boost source code matching to your distro.
23 *
24 * - Goto libs/math/minimax and replace f.cpp with this file.
25 *
26 * - Build as
27 *
28 *   g++ -o minimax -I /path/to/ntl/include main.cpp f.cpp /path/to/ntl/src/ntl.a
29 *
30 * - Run as
31 *
32 *    ./minimax
33 *
34 * - For example, to compute exp2 5th order polynomial between [0, 1] do:
35 *
36 *    variant 0
37 *    range 0 1
38 *    order 5 0
39 *    step 200
40 *    info
41 *
42 *  and take the coefficients from the P = { ... } array.
43 *
44 * - To compute log2 5th order polynomial between [1, 2] do:
45 *
46 *    variant 1
47 *    range 1 2
48 *    order 5 0
49 *    step 200
50 *    info
51 *
52 * - For more info see
53 * http://www.boost.org/doc/libs/1_47_0/libs/math/doc/sf_and_dist/html/math_toolkit/toolkit/internals2/minimax.html
54 */
55
56#define L22
57#include <boost/math/bindings/rr.hpp>
58#include <boost/math/tools/polynomial.hpp>
59
60#include <cmath>
61
62boost::math::ntl::RR exp2(const boost::math::ntl::RR& x)
63{
64      return exp(x*log(2.0));
65}
66
67boost::math::ntl::RR log2(const boost::math::ntl::RR& x)
68{
69      return log(x)/log(2.0);
70}
71
72boost::math::ntl::RR f(const boost::math::ntl::RR& x, int variant)
73{
74   switch(variant)
75   {
76   case 0:
77      return exp2(x);
78
79   case 1:
80      return log2(x)/(x - 1.0);
81   }
82
83   return 0;
84}
85
86
87void show_extra(
88   const boost::math::tools::polynomial<boost::math::ntl::RR>& n,
89   const boost::math::tools::polynomial<boost::math::ntl::RR>& d,
90   const boost::math::ntl::RR& x_offset,
91   const boost::math::ntl::RR& y_offset,
92   int variant)
93{
94   switch(variant)
95   {
96   default:
97      // do nothing here...
98      ;
99   }
100}
101
102