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ecency-mobile/ios/Pods/boost-for-react-native/boost/math/tools/roots.hpp

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// (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)
#ifndef BOOST_MATH_TOOLS_NEWTON_SOLVER_HPP
#define BOOST_MATH_TOOLS_NEWTON_SOLVER_HPP
#ifdef _MSC_VER
#pragma once
#endif
#include <utility>
#include <boost/config/no_tr1/cmath.hpp>
#include <stdexcept>
#include <boost/math/tools/config.hpp>
#include <boost/cstdint.hpp>
#include <boost/assert.hpp>
#include <boost/throw_exception.hpp>
#ifdef BOOST_MSVC
#pragma warning(push)
#pragma warning(disable: 4512)
#endif
#include <boost/math/tools/tuple.hpp>
#ifdef BOOST_MSVC
#pragma warning(pop)
#endif
#include <boost/math/special_functions/sign.hpp>
#include <boost/math/tools/toms748_solve.hpp>
#include <boost/math/policies/error_handling.hpp>
namespace boost{ namespace math{ namespace tools{
namespace detail{
namespace dummy{
template<int n, class T>
typename T::value_type get(const T&) BOOST_MATH_NOEXCEPT(T);
}
template <class Tuple, class T>
void unpack_tuple(const Tuple& t, T& a, T& b) BOOST_MATH_NOEXCEPT(T)
{
using dummy::get;
// Use ADL to find the right overload for get:
a = get<0>(t);
b = get<1>(t);
}
template <class Tuple, class T>
void unpack_tuple(const Tuple& t, T& a, T& b, T& c) BOOST_MATH_NOEXCEPT(T)
{
using dummy::get;
// Use ADL to find the right overload for get:
a = get<0>(t);
b = get<1>(t);
c = get<2>(t);
}
template <class Tuple, class T>
inline void unpack_0(const Tuple& t, T& val) BOOST_MATH_NOEXCEPT(T)
{
using dummy::get;
// Rely on ADL to find the correct overload of get:
val = get<0>(t);
}
template <class T, class U, class V>
inline void unpack_tuple(const std::pair<T, U>& p, V& a, V& b) BOOST_MATH_NOEXCEPT(T)
{
a = p.first;
b = p.second;
}
template <class T, class U, class V>
inline void unpack_0(const std::pair<T, U>& p, V& a) BOOST_MATH_NOEXCEPT(T)
{
a = p.first;
}
template <class F, class T>
void handle_zero_derivative(F f,
T& last_f0,
const T& f0,
T& delta,
T& result,
T& guess,
const T& min,
const T& max) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
if(last_f0 == 0)
{
// this must be the first iteration, pretend that we had a
// previous one at either min or max:
if(result == min)
{
guess = max;
}
else
{
guess = min;
}
unpack_0(f(guess), last_f0);
delta = guess - result;
}
if(sign(last_f0) * sign(f0) < 0)
{
// we've crossed over so move in opposite direction to last step:
if(delta < 0)
{
delta = (result - min) / 2;
}
else
{
delta = (result - max) / 2;
}
}
else
{
// move in same direction as last step:
if(delta < 0)
{
delta = (result - max) / 2;
}
else
{
delta = (result - min) / 2;
}
}
}
} // namespace
template <class F, class T, class Tol, class Policy>
std::pair<T, T> bisect(F f, T min, T max, Tol tol, boost::uintmax_t& max_iter, const Policy& pol) BOOST_NOEXCEPT_IF(policies::is_noexcept_error_policy<Policy>::value && BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
T fmin = f(min);
T fmax = f(max);
if(fmin == 0)
{
max_iter = 2;
return std::make_pair(min, min);
}
if(fmax == 0)
{
max_iter = 2;
return std::make_pair(max, max);
}
//
// Error checking:
//
static const char* function = "boost::math::tools::bisect<%1%>";
if(min >= max)
{
return boost::math::detail::pair_from_single(policies::raise_evaluation_error(function,
"Arguments in wrong order in boost::math::tools::bisect (first arg=%1%)", min, pol));
}
if(fmin * fmax >= 0)
{
return boost::math::detail::pair_from_single(policies::raise_evaluation_error(function,
"No change of sign in boost::math::tools::bisect, either there is no root to find, or there are multiple roots in the interval (f(min) = %1%).", fmin, pol));
}
//
// Three function invocations so far:
//
boost::uintmax_t count = max_iter;
if(count < 3)
count = 0;
else
count -= 3;
while(count && (0 == tol(min, max)))
{
T mid = (min + max) / 2;
T fmid = f(mid);
if((mid == max) || (mid == min))
break;
if(fmid == 0)
{
min = max = mid;
break;
}
else if(sign(fmid) * sign(fmin) < 0)
{
max = mid;
fmax = fmid;
}
else
{
min = mid;
fmin = fmid;
}
--count;
}
max_iter -= count;
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Bisection iteration, final count = " << max_iter << std::endl;
static boost::uintmax_t max_count = 0;
if(max_iter > max_count)
{
max_count = max_iter;
std::cout << "Maximum iterations: " << max_iter << std::endl;
}
#endif
return std::make_pair(min, max);
}
template <class F, class T, class Tol>
inline std::pair<T, T> bisect(F f, T min, T max, Tol tol, boost::uintmax_t& max_iter) BOOST_NOEXCEPT_IF(policies::is_noexcept_error_policy<policies::policy<> >::value && BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
return bisect(f, min, max, tol, max_iter, policies::policy<>());
}
template <class F, class T, class Tol>
inline std::pair<T, T> bisect(F f, T min, T max, Tol tol) BOOST_NOEXCEPT_IF(policies::is_noexcept_error_policy<policies::policy<> >::value && BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
boost::uintmax_t m = (std::numeric_limits<boost::uintmax_t>::max)();
return bisect(f, min, max, tol, m, policies::policy<>());
}
template <class F, class T>
T newton_raphson_iterate(F f, T guess, T min, T max, int digits, boost::uintmax_t& max_iter) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
BOOST_MATH_STD_USING
T f0(0), f1, last_f0(0);
T result = guess;
T factor = static_cast<T>(ldexp(1.0, 1 - digits));
T delta = tools::max_value<T>();
T delta1 = tools::max_value<T>();
T delta2 = tools::max_value<T>();
boost::uintmax_t count(max_iter);
do{
last_f0 = f0;
delta2 = delta1;
delta1 = delta;
detail::unpack_tuple(f(result), f0, f1);
--count;
if(0 == f0)
break;
if(f1 == 0)
{
// Oops zero derivative!!!
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Newton iteration, zero derivative found" << std::endl;
#endif
detail::handle_zero_derivative(f, last_f0, f0, delta, result, guess, min, max);
}
else
{
delta = f0 / f1;
}
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Newton iteration, delta = " << delta << std::endl;
#endif
if(fabs(delta * 2) > fabs(delta2))
{
// last two steps haven't converged, try bisection:
delta = (delta > 0) ? (result - min) / 2 : (result - max) / 2;
}
guess = result;
result -= delta;
if(result <= min)
{
delta = 0.5F * (guess - min);
result = guess - delta;
if((result == min) || (result == max))
break;
}
else if(result >= max)
{
delta = 0.5F * (guess - max);
result = guess - delta;
if((result == min) || (result == max))
break;
}
// update brackets:
if(delta > 0)
max = guess;
else
min = guess;
}while(count && (fabs(result * factor) < fabs(delta)));
max_iter -= count;
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Newton Raphson iteration, final count = " << max_iter << std::endl;
static boost::uintmax_t max_count = 0;
if(max_iter > max_count)
{
max_count = max_iter;
std::cout << "Maximum iterations: " << max_iter << std::endl;
}
#endif
return result;
}
template <class F, class T>
inline T newton_raphson_iterate(F f, T guess, T min, T max, int digits) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
boost::uintmax_t m = (std::numeric_limits<boost::uintmax_t>::max)();
return newton_raphson_iterate(f, guess, min, max, digits, m);
}
namespace detail{
struct halley_step
{
template <class T>
static T step(const T& /*x*/, const T& f0, const T& f1, const T& f2) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T))
{
using std::fabs;
T denom = 2 * f0;
T num = 2 * f1 - f0 * (f2 / f1);
T delta;
BOOST_MATH_INSTRUMENT_VARIABLE(denom);
BOOST_MATH_INSTRUMENT_VARIABLE(num);
if((fabs(num) < 1) && (fabs(denom) >= fabs(num) * tools::max_value<T>()))
{
// possible overflow, use Newton step:
delta = f0 / f1;
}
else
delta = denom / num;
return delta;
}
};
template <class Stepper, class F, class T>
T second_order_root_finder(F f, T guess, T min, T max, int digits, boost::uintmax_t& max_iter) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
BOOST_MATH_STD_USING
T f0(0), f1, f2;
T result = guess;
T factor = static_cast<T>(ldexp(1.0, 1 - digits));
T delta = (std::max)(T(10000000 * guess), T(10000000)); // arbitarily large delta
T last_f0 = 0;
T delta1 = delta;
T delta2 = delta;
bool out_of_bounds_sentry = false;
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Second order root iteration, limit = " << factor << std::endl;
#endif
boost::uintmax_t count(max_iter);
do{
last_f0 = f0;
delta2 = delta1;
delta1 = delta;
detail::unpack_tuple(f(result), f0, f1, f2);
--count;
BOOST_MATH_INSTRUMENT_VARIABLE(f0);
BOOST_MATH_INSTRUMENT_VARIABLE(f1);
BOOST_MATH_INSTRUMENT_VARIABLE(f2);
if(0 == f0)
break;
if(f1 == 0)
{
// Oops zero derivative!!!
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Second order root iteration, zero derivative found" << std::endl;
#endif
detail::handle_zero_derivative(f, last_f0, f0, delta, result, guess, min, max);
}
else
{
if(f2 != 0)
{
delta = Stepper::step(result, f0, f1, f2);
if(delta * f1 / f0 < 0)
{
// Oh dear, we have a problem as Newton and Halley steps
// disagree about which way we should move. Probably
// there is cancelation error in the calculation of the
// Halley step, or else the derivatives are so small
// that their values are basically trash. We will move
// in the direction indicated by a Newton step, but
// by no more than twice the current guess value, otherwise
// we can jump way out of bounds if we're not careful.
// See https://svn.boost.org/trac/boost/ticket/8314.
delta = f0 / f1;
if(fabs(delta) > 2 * fabs(guess))
delta = (delta < 0 ? -1 : 1) * 2 * fabs(guess);
}
}
else
delta = f0 / f1;
}
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Second order root iteration, delta = " << delta << std::endl;
#endif
T convergence = fabs(delta / delta2);
if((convergence > 0.8) && (convergence < 2))
{
// last two steps haven't converged, try bisection:
delta = (delta > 0) ? (result - min) / 2 : (result - max) / 2;
if(fabs(delta) > result)
delta = sign(delta) * result; // protect against huge jumps!
// reset delta2 so that this branch will *not* be taken on the
// next iteration:
delta2 = delta * 3;
BOOST_MATH_INSTRUMENT_VARIABLE(delta);
}
guess = result;
result -= delta;
BOOST_MATH_INSTRUMENT_VARIABLE(result);
// check for out of bounds step:
if(result < min)
{
T diff = ((fabs(min) < 1) && (fabs(result) > 1) && (tools::max_value<T>() / fabs(result) < fabs(min))) ? T(1000) : T(result / min);
if(fabs(diff) < 1)
diff = 1 / diff;
if(!out_of_bounds_sentry && (diff > 0) && (diff < 3))
{
// Only a small out of bounds step, lets assume that the result
// is probably approximately at min:
delta = 0.99f * (guess - min);
result = guess - delta;
out_of_bounds_sentry = true; // only take this branch once!
}
else
{
delta = (guess - min) / 2;
result = guess - delta;
if((result == min) || (result == max))
break;
}
}
else if(result > max)
{
T diff = ((fabs(max) < 1) && (fabs(result) > 1) && (tools::max_value<T>() / fabs(result) < fabs(max))) ? T(1000) : T(result / max);
if(fabs(diff) < 1)
diff = 1 / diff;
if(!out_of_bounds_sentry && (diff > 0) && (diff < 3))
{
// Only a small out of bounds step, lets assume that the result
// is probably approximately at min:
delta = 0.99f * (guess - max);
result = guess - delta;
out_of_bounds_sentry = true; // only take this branch once!
}
else
{
delta = (guess - max) / 2;
result = guess - delta;
if((result == min) || (result == max))
break;
}
}
// update brackets:
if(delta > 0)
max = guess;
else
min = guess;
} while(count && (fabs(result * factor) < fabs(delta)));
max_iter -= count;
#ifdef BOOST_MATH_INSTRUMENT
std::cout << "Second order root iteration, final count = " << max_iter << std::endl;
#endif
return result;
}
}
template <class F, class T>
T halley_iterate(F f, T guess, T min, T max, int digits, boost::uintmax_t& max_iter) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
return detail::second_order_root_finder<detail::halley_step>(f, guess, min, max, digits, max_iter);
}
template <class F, class T>
inline T halley_iterate(F f, T guess, T min, T max, int digits) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
boost::uintmax_t m = (std::numeric_limits<boost::uintmax_t>::max)();
return halley_iterate(f, guess, min, max, digits, m);
}
namespace detail{
struct schroder_stepper
{
template <class T>
static T step(const T& x, const T& f0, const T& f1, const T& f2) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T))
{
T ratio = f0 / f1;
T delta;
if(ratio / x < 0.1)
{
delta = ratio + (f2 / (2 * f1)) * ratio * ratio;
// check second derivative doesn't over compensate:
if(delta * ratio < 0)
delta = ratio;
}
else
delta = ratio; // fall back to Newton iteration.
return delta;
}
};
}
template <class F, class T>
T schroder_iterate(F f, T guess, T min, T max, int digits, boost::uintmax_t& max_iter) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
return detail::second_order_root_finder<detail::schroder_stepper>(f, guess, min, max, digits, max_iter);
}
template <class F, class T>
inline T schroder_iterate(F f, T guess, T min, T max, int digits) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
boost::uintmax_t m = (std::numeric_limits<boost::uintmax_t>::max)();
return schroder_iterate(f, guess, min, max, digits, m);
}
//
// These two are the old spelling of this function, retained for backwards compatibity just in case:
//
template <class F, class T>
T schroeder_iterate(F f, T guess, T min, T max, int digits, boost::uintmax_t& max_iter) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
return detail::second_order_root_finder<detail::schroder_stepper>(f, guess, min, max, digits, max_iter);
}
template <class F, class T>
inline T schroeder_iterate(F f, T guess, T min, T max, int digits) BOOST_NOEXCEPT_IF(BOOST_MATH_IS_FLOAT(T) && noexcept(std::declval<F>()(std::declval<T>())))
{
boost::uintmax_t m = (std::numeric_limits<boost::uintmax_t>::max)();
return schroder_iterate(f, guess, min, max, digits, m);
}
} // namespace tools
} // namespace math
} // namespace boost
#endif // BOOST_MATH_TOOLS_NEWTON_SOLVER_HPP
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