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/**************************************************************************
*
* (C) Copyright VMware, Inc 2010.
* (C) Copyright John Maddock 2006.
* Use, modification and distribution are subject to the
* Boost Software License, Version 1.0. (See accompanying file
* LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*
**************************************************************************/
/*
* This file allows to compute the minimax polynomial coefficients we use
* for fast exp2/log2.
*
* How to use this source:
*
* - Download and build the NTL library from
* http://shoup.net/ntl/download.html , or install libntl-dev package if on
* Debian.
*
* - Download boost source code matching to your distro.
*
* - Goto libs/math/minimax and replace f.cpp with this file.
*
* - Build as
*
* g++ -o minimax -I /path/to/ntl/include main.cpp f.cpp /path/to/ntl/src/ntl.a
*
* - Run as
*
* ./minimax
*
* - For example, to compute log2 5th order polynomial between [1, 2] do:
*
* variant 0
* range 1 2
* order 5 0
* step 200
* info
*
* and take the coefficients from the P = { ... } array.
*
* - To compute exp2 5th order polynomial between [0, 1] do:
*
* variant 1
* range 0 1
* order 5 0
* step 200
* info
*
* - For more info see
* http://www.boost.org/doc/libs/1_47_0/libs/math/doc/sf_and_dist/html/math_toolkit/toolkit/internals2/minimax.html
*/
#define L22
#include <boost/math/bindings/rr.hpp>
#include <boost/math/tools/polynomial.hpp>
#include <cmath>
boost::math::ntl::RR f(const boost::math::ntl::RR& x, int variant)
{
static const boost::math::ntl::RR tiny = boost::math::tools::min_value<boost::math::ntl::RR>() * 64;
switch(variant)
{
case 0:
// log2(x)/(x - 1)
return log(x)/log(2.0)/(x - 1.0);
case 1:
// exp2(x)
return exp(x*log(2.0));
}
return 0;
}
void show_extra(
const boost::math::tools::polynomial<boost::math::ntl::RR>& n,
const boost::math::tools::polynomial<boost::math::ntl::RR>& d,
const boost::math::ntl::RR& x_offset,
const boost::math::ntl::RR& y_offset,
int variant)
{
switch(variant)
{
default:
// do nothing here...
;
}
}
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