f.cpp revision 3464ebd5 
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 abuild the NTL library from
19 *   http://shoup.net/ntl/download.html
20 *
21 * - Download boost source code matching to your distro.
22 *
23 * - Goto libs/math/minimax and replace f.cpp with this file.
24 *
25 * - Build as
26 *
27 *   g++ -o minimax -I /path/to/ntl/include main.cpp f.cpp /path/to/ntl/src/ntl.a -lboost_math_tr1
28 *
29 * - Run as
30 *
31 *    ./minimax
32 *
33 * - For example, to compute exp2 5th order polynomial between [0, 1] do:
34 *
35 *    variant 1
36 *    range 0 1
37 *    order 5 0
38 *    steps 200
39 *    info
40 *
41 * - For more info see
42 * http://www.boost.org/doc/libs/1_36_0/libs/math/doc/sf_and_dist/html/math_toolkit/toolkit/internals2/minimax.html
43 */
44
45#define L22
46#include <boost/math/bindings/rr.hpp>
47#include <boost/math/tools/polynomial.hpp>
48
49#include <cmath>
50
51
52boost::math::ntl::RR f(const boost::math::ntl::RR& x, int variant)
53{
54   static const boost::math::ntl::RR tiny = boost::math::tools::min_value<boost::math::ntl::RR>() * 64;
55
56   switch(variant)
57   {
58   case 0:
59      // log2(x)/(x - 1)
60      return log(x)/log(2.0)/(x - 1.0);
61
62   case 1:
63      // exp2(x)
64      return exp(x*log(2.0));
65   }
66
67   return 0;
68}
69
70
71void show_extra(
72   const boost::math::tools::polynomial<boost::math::ntl::RR>& n,
73   const boost::math::tools::polynomial<boost::math::ntl::RR>& d,
74   const boost::math::ntl::RR& x_offset,
75   const boost::math::ntl::RR& y_offset,
76   int variant)
77{
78   switch(variant)
79   {
80   default:
81      // do nothing here...
82      ;
83   }
84}
85
86