102 lines · plain
1// (C) Copyright John Maddock 2006.2// (C) Copyright Matt Borland 2024.3// Use, modification and distribution are subject to the4// Boost Software License, Version 1.0. (See accompanying file5// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)6 7#ifndef BOOST_MATH_POWM18#define BOOST_MATH_POWM19 10#ifdef _MSC_VER11#pragma once12#pragma warning(push)13#pragma warning(disable:4702) // Unreachable code (release mode only warning)14#endif15 16#include <boost/math/tools/config.hpp>17#include <boost/math/special_functions/math_fwd.hpp>18#include <boost/math/special_functions/log1p.hpp>19#include <boost/math/special_functions/expm1.hpp>20#include <boost/math/special_functions/trunc.hpp>21#include <boost/math/special_functions/sign.hpp>22#include <boost/math/tools/assert.hpp>23 24namespace boost{ namespace math{ namespace detail{25 26template <class T, class Policy>27BOOST_MATH_GPU_ENABLED inline T powm1_imp(const T x, const T y, const Policy& pol)28{29 BOOST_MATH_STD_USING30 constexpr auto function = "boost::math::powm1<%1%>(%1%, %1%)";31 32 if ((fabs(y * (x - 1)) < T(0.5)) || (fabs(y) < T(0.2)))33 {34 // We don't have any good/quick approximation for log(x) * y35 // so just try it and see:36 T l = y * log(x);37 if (l < T(0.5))38 return boost::math::expm1(l, pol);39 if (l > boost::math::tools::log_max_value<T>())40 return boost::math::policies::raise_overflow_error<T>(function, nullptr, pol);41 // fall through....42 }43 44 T result = pow(x, y) - 1;45 if((boost::math::isinf)(result))46 return result < 0 ? -boost::math::policies::raise_overflow_error<T>(function, nullptr, pol) : boost::math::policies::raise_overflow_error<T>(function, nullptr, pol);47 if((boost::math::isnan)(result))48 return boost::math::policies::raise_domain_error<T>(function, "Result of pow is complex or undefined", x, pol);49 return result;50}51 52template <class T, class Policy>53BOOST_MATH_GPU_ENABLED inline T powm1_imp_dispatch(const T x, const T y, const Policy& pol)54{55 BOOST_MATH_STD_USING56 57 if ((boost::math::signbit)(x)) // Need to error check -0 here as well58 {59 constexpr auto function = "boost::math::powm1<%1%>(%1%, %1%)";60 61 // y had better be an integer:62 if (boost::math::trunc(y) != y)63 return boost::math::policies::raise_domain_error<T>(function, "For non-integral exponent, expected base > 0 but got %1%", x, pol);64 if (boost::math::trunc(y / 2) == y / 2)65 return powm1_imp(T(-x), T(y), pol);66 }67 68 return powm1_imp(T(x), T(y), pol);69}70 71} // detail72 73template <class T1, class T2>74BOOST_MATH_GPU_ENABLED inline typename tools::promote_args<T1, T2>::type75 powm1(const T1 a, const T2 z)76{77 typedef typename tools::promote_args<T1, T2>::type result_type;78 return detail::powm1_imp_dispatch(static_cast<result_type>(a), static_cast<result_type>(z), policies::policy<>());79}80 81template <class T1, class T2, class Policy>82BOOST_MATH_GPU_ENABLED inline typename tools::promote_args<T1, T2>::type83 powm1(const T1 a, const T2 z, const Policy& pol)84{85 typedef typename tools::promote_args<T1, T2>::type result_type;86 return detail::powm1_imp_dispatch(static_cast<result_type>(a), static_cast<result_type>(z), pol);87}88 89} // namespace math90} // namespace boost91 92#ifdef _MSC_VER93#pragma warning(pop)94#endif95 96#endif // BOOST_MATH_POWM197 98 99 100 101 102