ceph/src/boost/boost/math/special_functions/ulp.hpp

   1 //  (C) Copyright John Maddock 2015.
   2 //  Use, modification and distribution are subject to the
   3 //  Boost Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef BOOST_MATH_SPECIAL_ULP_HPP
   7 #define BOOST_MATH_SPECIAL_ULP_HPP
   8
   9 #ifdef _MSC_VER
  10 #pragma once
  11 #endif
  12
  13 #include <boost/math/special_functions/math_fwd.hpp>
  14 #include <boost/math/policies/error_handling.hpp>
  15 #include <boost/math/special_functions/fpclassify.hpp>
  16 #include <boost/math/special_functions/next.hpp>
  17
  18 namespace boost{ namespace math{ namespace detail{
  19
  20 template <class T, class Policy>
  21 T ulp_imp(const T& val, const mpl::true_&, const Policy& pol)
  22 {
  23    BOOST_MATH_STD_USING
  24    int expon;
  25    static const char* function = "ulp<%1%>(%1%)";
  26
  27    int fpclass = (boost::math::fpclassify)(val);
  28
  29    if(fpclass == (int)FP_NAN)
  30    {
  31       return policies::raise_domain_error<T>(
  32          function,
  33          "Argument must be finite, but got %1%", val, pol);
  34    }
  35    else if((fpclass == (int)FP_INFINITE) || (fabs(val) >= tools::max_value<T>()))
  36    {
  37       return (val < 0 ? -1 : 1) * policies::raise_overflow_error<T>(function, 0, pol);
  38    }
  39    else if(fpclass == FP_ZERO)
  40       return detail::get_smallest_value<T>();
  41    //
  42    // This code is almost the same as that for float_next, except for negative integers,
  43    // where we preserve the relation ulp(x) == ulp(-x) as does Java:
  44    //
  45    frexp(fabs(val), &expon);
  46    T diff = ldexp(T(1), expon - tools::digits<T>());
  47    if(diff == 0)
  48       diff = detail::get_smallest_value<T>();
  49    return diff;
  50 }
  51 // non-binary version:
  52 template <class T, class Policy>
  53 T ulp_imp(const T& val, const mpl::false_&, const Policy& pol)
  54 {
  55    BOOST_STATIC_ASSERT(std::numeric_limits<T>::is_specialized);
  56    BOOST_STATIC_ASSERT(std::numeric_limits<T>::radix != 2);
  57    BOOST_MATH_STD_USING
  58    int expon;
  59    static const char* function = "ulp<%1%>(%1%)";
  60
  61    int fpclass = (boost::math::fpclassify)(val);
  62
  63    if(fpclass == (int)FP_NAN)
  64    {
  65       return policies::raise_domain_error<T>(
  66          function,
  67          "Argument must be finite, but got %1%", val, pol);
  68    }
  69    else if((fpclass == (int)FP_INFINITE) || (fabs(val) >= tools::max_value<T>()))
  70    {
  71       return (val < 0 ? -1 : 1) * policies::raise_overflow_error<T>(function, 0, pol);
  72    }
  73    else if(fpclass == FP_ZERO)
  74       return detail::get_smallest_value<T>();
  75    //
  76    // This code is almost the same as that for float_next, except for negative integers,
  77    // where we preserve the relation ulp(x) == ulp(-x) as does Java:
  78    //
  79    expon = 1 + ilogb(fabs(val));
  80    T diff = scalbn(T(1), expon - std::numeric_limits<T>::digits);
  81    if(diff == 0)
  82       diff = detail::get_smallest_value<T>();
  83    return diff;
  84 }
  85
  86 }
  87
  88 template <class T, class Policy>
  89 inline typename tools::promote_args<T>::type ulp(const T& val, const Policy& pol)
  90 {
  91    typedef typename tools::promote_args<T>::type result_type;
  92    return detail::ulp_imp(static_cast<result_type>(val), mpl::bool_<!std::numeric_limits<result_type>::is_specialized || (std::numeric_limits<result_type>::radix == 2)>(), pol);
  93 }
  94
  95 template <class T>
  96 inline typename tools::promote_args<T>::type ulp(const T& val)
  97 {
  98    return ulp(val, policies::policy<>());
  99 }
 100
 101
 102 }} // namespaces
 103
 104 #endif // BOOST_MATH_SPECIAL_ULP_HPP
 105