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			635 lines
		
	
	
		
			22 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
|   | //  Copyright 2014 Marco Guazzone (marco.guazzone@gmail.com) | ||
|  | // | ||
|  | //  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 module implements the Hyper-Exponential distribution. | ||
|  | // | ||
|  | // References: | ||
|  | // - "Queueing Theory in Manufacturing Systems Analysis and Design" by H.T. Papadopolous, C. Heavey and J. Browne (Chapman & Hall/CRC, 1993) | ||
|  | // - http://reference.wolfram.com/language/ref/HyperexponentialDistribution.html | ||
|  | // - http://en.wikipedia.org/wiki/Hyperexponential_distribution | ||
|  | // | ||
|  | 
 | ||
|  | #ifndef BOOST_MATH_DISTRIBUTIONS_HYPEREXPONENTIAL_HPP | ||
|  | #define BOOST_MATH_DISTRIBUTIONS_HYPEREXPONENTIAL_HPP | ||
|  | 
 | ||
|  | 
 | ||
|  | #include <boost/config.hpp> | ||
|  | #include <boost/math/distributions/complement.hpp> | ||
|  | #include <boost/math/distributions/detail/common_error_handling.hpp> | ||
|  | #include <boost/math/distributions/exponential.hpp> | ||
|  | #include <boost/math/policies/policy.hpp> | ||
|  | #include <boost/math/special_functions/fpclassify.hpp> | ||
|  | #include <boost/math/tools/precision.hpp> | ||
|  | #include <boost/math/tools/roots.hpp> | ||
|  | #include <boost/range/begin.hpp> | ||
|  | #include <boost/range/end.hpp> | ||
|  | #include <boost/range/size.hpp> | ||
|  | #include <boost/type_traits/has_pre_increment.hpp> | ||
|  | #include <cstddef> | ||
|  | #include <iterator> | ||
|  | #include <limits> | ||
|  | #include <numeric> | ||
|  | #include <utility> | ||
|  | #include <vector> | ||
|  | 
 | ||
|  | #if !defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST) | ||
|  | # include <initializer_list> | ||
|  | #endif | ||
|  | 
 | ||
|  | #ifdef _MSC_VER | ||
|  | # pragma warning (push) | ||
|  | # pragma warning(disable:4127) // conditional expression is constant | ||
|  | # pragma warning(disable:4389) // '==' : signed/unsigned mismatch in test_tools | ||
|  | #endif // _MSC_VER | ||
|  | 
 | ||
|  | namespace boost { namespace math { | ||
|  | 
 | ||
|  | namespace detail { | ||
|  | 
 | ||
|  | template <typename Dist> | ||
|  | typename Dist::value_type generic_quantile(const Dist& dist, const typename Dist::value_type& p, const typename Dist::value_type& guess, bool comp, const char* function); | ||
|  | 
 | ||
|  | } // Namespace detail | ||
|  | 
 | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | class hyperexponential_distribution; | ||
|  | 
 | ||
|  | 
 | ||
|  | namespace /*<unnamed>*/ { namespace hyperexp_detail { | ||
|  | 
 | ||
|  | template <typename T> | ||
|  | void normalize(std::vector<T>& v) | ||
|  | { | ||
|  |    if(!v.size()) | ||
|  |       return;  // Our error handlers will get this later | ||
|  |     const T sum = std::accumulate(v.begin(), v.end(), static_cast<T>(0)); | ||
|  |     T final_sum = 0; | ||
|  |     const typename std::vector<T>::iterator end = --v.end(); | ||
|  |     for (typename std::vector<T>::iterator it = v.begin(); | ||
|  |          it != end; | ||
|  |          ++it) | ||
|  |     { | ||
|  |         *it /= sum; | ||
|  |         final_sum += *it; | ||
|  |     } | ||
|  |     *end = 1 - final_sum;  // avoids round off errors, ensures the probs really do sum to 1. | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | bool check_probabilities(char const* function, std::vector<RealT> const& probabilities, RealT* presult, PolicyT const& pol) | ||
|  | { | ||
|  |     BOOST_MATH_STD_USING | ||
|  |     const std::size_t n = probabilities.size(); | ||
|  |     RealT sum = 0; | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         if (probabilities[i] < 0 | ||
|  |             || probabilities[i] > 1 | ||
|  |             || !(boost::math::isfinite)(probabilities[i])) | ||
|  |         { | ||
|  |             *presult = policies::raise_domain_error<RealT>(function, | ||
|  |                                                            "The elements of parameter \"probabilities\" must be >= 0 and <= 1, but at least one of them was: %1%.", | ||
|  |                                                            probabilities[i], | ||
|  |                                                            pol); | ||
|  |             return false; | ||
|  |         } | ||
|  |         sum += probabilities[i]; | ||
|  |     } | ||
|  | 
 | ||
|  |     // | ||
|  |     // We try to keep phase probabilities correctly normalized in the distribution constructors, | ||
|  |     // however in practice we have to allow for a very slight divergence from a sum of exactly 1: | ||
|  |     // | ||
|  |     if (fabs(sum - 1) > tools::epsilon<RealT>() * 2) | ||
|  |     { | ||
|  |         *presult = policies::raise_domain_error<RealT>(function, | ||
|  |                                                        "The elements of parameter \"probabilities\" must sum to 1, but their sum is: %1%.", | ||
|  |                                                        sum, | ||
|  |                                                        pol); | ||
|  |         return false; | ||
|  |     } | ||
|  | 
 | ||
|  |     return true; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | bool check_rates(char const* function, std::vector<RealT> const& rates, RealT* presult, PolicyT const& pol) | ||
|  | { | ||
|  |     const std::size_t n = rates.size(); | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         if (rates[i] <= 0 | ||
|  |             || !(boost::math::isfinite)(rates[i])) | ||
|  |         { | ||
|  |             *presult = policies::raise_domain_error<RealT>(function, | ||
|  |                                                            "The elements of parameter \"rates\" must be > 0, but at least one of them is: %1%.", | ||
|  |                                                            rates[i], | ||
|  |                                                            pol); | ||
|  |             return false; | ||
|  |         } | ||
|  |     } | ||
|  |     return true; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | bool check_dist(char const* function, std::vector<RealT> const& probabilities, std::vector<RealT> const& rates, RealT* presult, PolicyT const& pol) | ||
|  | { | ||
|  |     BOOST_MATH_STD_USING | ||
|  |     if (probabilities.size() != rates.size()) | ||
|  |     { | ||
|  |         *presult = policies::raise_domain_error<RealT>(function, | ||
|  |                                                        "The parameters \"probabilities\" and \"rates\" must have the same length, but their size differ by: %1%.", | ||
|  |                                                        fabs(static_cast<RealT>(probabilities.size())-static_cast<RealT>(rates.size())), | ||
|  |                                                        pol); | ||
|  |         return false; | ||
|  |     } | ||
|  | 
 | ||
|  |     return check_probabilities(function, probabilities, presult, pol) | ||
|  |            && check_rates(function, rates, presult, pol); | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | bool check_x(char const* function, RealT x, RealT* presult, PolicyT const& pol) | ||
|  | { | ||
|  |     if (x < 0 || (boost::math::isnan)(x)) | ||
|  |     { | ||
|  |         *presult = policies::raise_domain_error<RealT>(function, "The random variable must be >= 0, but is: %1%.", x, pol); | ||
|  |         return false; | ||
|  |     } | ||
|  |     return true; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | bool check_probability(char const* function, RealT p, RealT* presult, PolicyT const& pol) | ||
|  | { | ||
|  |     if (p < 0 || p > 1 || (boost::math::isnan)(p)) | ||
|  |     { | ||
|  |         *presult = policies::raise_domain_error<RealT>(function, "The probability be >= 0 and <= 1, but is: %1%.", p, pol); | ||
|  |         return false; | ||
|  |     } | ||
|  |     return true; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT quantile_impl(hyperexponential_distribution<RealT, PolicyT> const& dist, RealT const& p, bool comp) | ||
|  | { | ||
|  |     // Don't have a closed form so try to numerically solve the inverse CDF... | ||
|  | 
 | ||
|  |     typedef typename policies::evaluation<RealT, PolicyT>::type value_type; | ||
|  |     typedef typename policies::normalise<PolicyT, | ||
|  |                                          policies::promote_float<false>, | ||
|  |                                          policies::promote_double<false>, | ||
|  |                                          policies::discrete_quantile<>, | ||
|  |                                          policies::assert_undefined<> >::type forwarding_policy; | ||
|  | 
 | ||
|  |     static const char* function = comp ? "boost::math::quantile(const boost::math::complemented2_type<boost::math::hyperexponential_distribution<%1%>, %1%>&)" | ||
|  |                                        : "boost::math::quantile(const boost::math::hyperexponential_distribution<%1%>&, %1%)"; | ||
|  | 
 | ||
|  |     RealT result = 0; | ||
|  | 
 | ||
|  |     if (!check_probability(function, p, &result, PolicyT())) | ||
|  |     { | ||
|  |         return result; | ||
|  |     } | ||
|  | 
 | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     // A possible (but inaccurate) approximation is given below, where the | ||
|  |     // quantile is given by the weighted sum of exponential quantiles: | ||
|  |     RealT guess = 0; | ||
|  |     if (comp) | ||
|  |     { | ||
|  |         for (std::size_t i = 0; i < n; ++i) | ||
|  |         { | ||
|  |             const exponential_distribution<RealT,PolicyT> exp(rates[i]); | ||
|  | 
 | ||
|  |             guess += probs[i]*quantile(complement(exp, p)); | ||
|  |         } | ||
|  |     } | ||
|  |     else | ||
|  |     { | ||
|  |         for (std::size_t i = 0; i < n; ++i) | ||
|  |         { | ||
|  |             const exponential_distribution<RealT,PolicyT> exp(rates[i]); | ||
|  | 
 | ||
|  |             guess += probs[i]*quantile(exp, p); | ||
|  |         } | ||
|  |     } | ||
|  | 
 | ||
|  |     // Fast return in case the Hyper-Exponential is essentially an Exponential | ||
|  |     if (n == 1) | ||
|  |     { | ||
|  |         return guess; | ||
|  |     } | ||
|  | 
 | ||
|  |     value_type q; | ||
|  |     q = detail::generic_quantile(hyperexponential_distribution<RealT,forwarding_policy>(probs, rates), | ||
|  |                                  p, | ||
|  |                                  guess, | ||
|  |                                  comp, | ||
|  |                                  function); | ||
|  | 
 | ||
|  |     result = policies::checked_narrowing_cast<RealT,forwarding_policy>(q, function); | ||
|  | 
 | ||
|  |     return result; | ||
|  | } | ||
|  | 
 | ||
|  | }} // Namespace <unnamed>::hyperexp_detail | ||
|  | 
 | ||
|  | 
 | ||
|  | template <typename RealT = double, typename PolicyT = policies::policy<> > | ||
|  | class hyperexponential_distribution | ||
|  | { | ||
|  |     public: typedef RealT value_type; | ||
|  |     public: typedef PolicyT policy_type; | ||
|  | 
 | ||
|  | 
 | ||
|  |     public: hyperexponential_distribution() | ||
|  |     : probs_(1, 1), | ||
|  |       rates_(1, 1) | ||
|  |     { | ||
|  |         RealT err; | ||
|  |         hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |                                     probs_, | ||
|  |                                     rates_, | ||
|  |                                     &err, | ||
|  |                                     PolicyT()); | ||
|  |     } | ||
|  | 
 | ||
|  |     // Four arg constructor: no ambiguity here, the arguments must be two pairs of iterators: | ||
|  |     public: template <typename ProbIterT, typename RateIterT> | ||
|  |             hyperexponential_distribution(ProbIterT prob_first, ProbIterT prob_last, | ||
|  |                                           RateIterT rate_first, RateIterT rate_last) | ||
|  |     : probs_(prob_first, prob_last), | ||
|  |       rates_(rate_first, rate_last) | ||
|  |     { | ||
|  |         hyperexp_detail::normalize(probs_); | ||
|  |         RealT err; | ||
|  |         hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |                                     probs_, | ||
|  |                                     rates_, | ||
|  |                                     &err, | ||
|  |                                     PolicyT()); | ||
|  |     } | ||
|  | 
 | ||
|  |     // Two arg constructor from 2 ranges, we SFINAE this out of existance if | ||
|  |     // either argument type is incrementable as in that case the type is | ||
|  |     // probably an iterator: | ||
|  |     public: template <typename ProbRangeT, typename RateRangeT> | ||
|  |             hyperexponential_distribution(ProbRangeT const& prob_range, | ||
|  |                                           RateRangeT const& rate_range, | ||
|  |                                           typename boost::disable_if_c<boost::has_pre_increment<ProbRangeT>::value || boost::has_pre_increment<RateRangeT>::value>::type* = 0) | ||
|  |     : probs_(boost::begin(prob_range), boost::end(prob_range)), | ||
|  |       rates_(boost::begin(rate_range), boost::end(rate_range)) | ||
|  |     { | ||
|  |         hyperexp_detail::normalize(probs_); | ||
|  | 
 | ||
|  |         RealT err; | ||
|  |         hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |                                     probs_, | ||
|  |                                     rates_, | ||
|  |                                     &err, | ||
|  |                                     PolicyT()); | ||
|  |     } | ||
|  | 
 | ||
|  |     // Two arg constructor for a pair of iterators: we SFINAE this out of | ||
|  |     // existance if neither argument types are incrementable. | ||
|  |     // Note that we allow different argument types here to allow for | ||
|  |     // construction from an array plus a pointer into that array. | ||
|  |     public: template <typename RateIterT, typename RateIterT2> | ||
|  |             hyperexponential_distribution(RateIterT const& rate_first,  | ||
|  |                                           RateIterT2 const& rate_last,  | ||
|  |                                           typename boost::enable_if_c<boost::has_pre_increment<RateIterT>::value || boost::has_pre_increment<RateIterT2>::value>::type* = 0) | ||
|  |     : probs_(std::distance(rate_first, rate_last), 1), // will be normalized below | ||
|  |       rates_(rate_first, rate_last) | ||
|  |     { | ||
|  |         hyperexp_detail::normalize(probs_); | ||
|  | 
 | ||
|  |         RealT err; | ||
|  |         hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |                                     probs_, | ||
|  |                                     rates_, | ||
|  |                                     &err, | ||
|  |                                     PolicyT()); | ||
|  |     } | ||
|  | 
 | ||
|  | #if !defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST) | ||
|  |       // Initializer list constructor: allows for construction from array literals: | ||
|  | public: hyperexponential_distribution(std::initializer_list<RealT> l1, std::initializer_list<RealT> l2) | ||
|  |       : probs_(l1.begin(), l1.end()), | ||
|  |         rates_(l2.begin(), l2.end()) | ||
|  |       { | ||
|  |          hyperexp_detail::normalize(probs_); | ||
|  | 
 | ||
|  |          RealT err; | ||
|  |          hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |             probs_, | ||
|  |             rates_, | ||
|  |             &err, | ||
|  |             PolicyT()); | ||
|  |       } | ||
|  | 
 | ||
|  | public: hyperexponential_distribution(std::initializer_list<RealT> l1) | ||
|  |       : probs_(l1.size(), 1), | ||
|  |         rates_(l1.begin(), l1.end()) | ||
|  |       { | ||
|  |          hyperexp_detail::normalize(probs_); | ||
|  | 
 | ||
|  |          RealT err; | ||
|  |          hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |             probs_, | ||
|  |             rates_, | ||
|  |             &err, | ||
|  |             PolicyT()); | ||
|  |       } | ||
|  | #endif // !defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST) | ||
|  | 
 | ||
|  |     // Single argument constructor: argument must be a range. | ||
|  |     public: template <typename RateRangeT> | ||
|  |     hyperexponential_distribution(RateRangeT const& rate_range) | ||
|  |     : probs_(boost::size(rate_range), 1), // will be normalized below | ||
|  |       rates_(boost::begin(rate_range), boost::end(rate_range)) | ||
|  |     { | ||
|  |         hyperexp_detail::normalize(probs_); | ||
|  | 
 | ||
|  |         RealT err; | ||
|  |         hyperexp_detail::check_dist("boost::math::hyperexponential_distribution<%1%>::hyperexponential_distribution", | ||
|  |                                     probs_, | ||
|  |                                     rates_, | ||
|  |                                     &err, | ||
|  |                                     PolicyT()); | ||
|  |     } | ||
|  | 
 | ||
|  |     public: std::vector<RealT> probabilities() const | ||
|  |     { | ||
|  |         return probs_; | ||
|  |     } | ||
|  | 
 | ||
|  |     public: std::vector<RealT> rates() const | ||
|  |     { | ||
|  |         return rates_; | ||
|  |     } | ||
|  | 
 | ||
|  |     public: std::size_t num_phases() const | ||
|  |     { | ||
|  |         return rates_.size(); | ||
|  |     } | ||
|  | 
 | ||
|  | 
 | ||
|  |     private: std::vector<RealT> probs_; | ||
|  |     private: std::vector<RealT> rates_; | ||
|  | }; // class hyperexponential_distribution | ||
|  | 
 | ||
|  | 
 | ||
|  | // Convenient type synonym for double. | ||
|  | typedef hyperexponential_distribution<double> hyperexponential; | ||
|  | 
 | ||
|  | 
 | ||
|  | // Range of permissible values for random variable x | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | std::pair<RealT,RealT> range(hyperexponential_distribution<RealT,PolicyT> const&) | ||
|  | { | ||
|  |     if (std::numeric_limits<RealT>::has_infinity) | ||
|  |     { | ||
|  |         return std::make_pair(static_cast<RealT>(0), std::numeric_limits<RealT>::infinity()); // 0 to +inf. | ||
|  |     } | ||
|  | 
 | ||
|  |     return std::make_pair(static_cast<RealT>(0), tools::max_value<RealT>()); // 0 to +<max value> | ||
|  | } | ||
|  | 
 | ||
|  | // Range of supported values for random variable x. | ||
|  | // This is range where cdf rises from 0 to 1, and outside it, the pdf is zero. | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | std::pair<RealT,RealT> support(hyperexponential_distribution<RealT,PolicyT> const&) | ||
|  | { | ||
|  |     return std::make_pair(tools::min_value<RealT>(), tools::max_value<RealT>()); // <min value> to +<max value>. | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT pdf(hyperexponential_distribution<RealT, PolicyT> const& dist, RealT const& x) | ||
|  | { | ||
|  |     BOOST_MATH_STD_USING | ||
|  |     RealT result = 0; | ||
|  | 
 | ||
|  |     if (!hyperexp_detail::check_x("boost::math::pdf(const boost::math::hyperexponential_distribution<%1%>&, %1%)", x, &result, PolicyT())) | ||
|  |     { | ||
|  |         return result; | ||
|  |     } | ||
|  | 
 | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         const exponential_distribution<RealT,PolicyT> exp(rates[i]); | ||
|  | 
 | ||
|  |         result += probs[i]*pdf(exp, x); | ||
|  |         //result += probs[i]*rates[i]*exp(-rates[i]*x); | ||
|  |     } | ||
|  | 
 | ||
|  |     return result; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT cdf(hyperexponential_distribution<RealT, PolicyT> const& dist, RealT const& x) | ||
|  | { | ||
|  |     RealT result = 0; | ||
|  | 
 | ||
|  |     if (!hyperexp_detail::check_x("boost::math::cdf(const boost::math::hyperexponential_distribution<%1%>&, %1%)", x, &result, PolicyT())) | ||
|  |     { | ||
|  |         return result; | ||
|  |     } | ||
|  | 
 | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         const exponential_distribution<RealT,PolicyT> exp(rates[i]); | ||
|  | 
 | ||
|  |         result += probs[i]*cdf(exp, x); | ||
|  |     } | ||
|  | 
 | ||
|  |     return result; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT quantile(hyperexponential_distribution<RealT, PolicyT> const& dist, RealT const& p) | ||
|  | { | ||
|  |     return hyperexp_detail::quantile_impl(dist, p , false); | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT cdf(complemented2_type<hyperexponential_distribution<RealT,PolicyT>, RealT> const& c) | ||
|  | { | ||
|  |     RealT const& x = c.param; | ||
|  |     hyperexponential_distribution<RealT,PolicyT> const& dist = c.dist; | ||
|  | 
 | ||
|  |     RealT result = 0; | ||
|  | 
 | ||
|  |     if (!hyperexp_detail::check_x("boost::math::cdf(boost::math::complemented2_type<const boost::math::hyperexponential_distribution<%1%>&, %1%>)", x, &result, PolicyT())) | ||
|  |     { | ||
|  |         return result; | ||
|  |     } | ||
|  | 
 | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         const exponential_distribution<RealT,PolicyT> exp(rates[i]); | ||
|  | 
 | ||
|  |         result += probs[i]*cdf(complement(exp, x)); | ||
|  |     } | ||
|  | 
 | ||
|  |     return result; | ||
|  | } | ||
|  | 
 | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT quantile(complemented2_type<hyperexponential_distribution<RealT, PolicyT>, RealT> const& c) | ||
|  | { | ||
|  |     RealT const& p = c.param; | ||
|  |     hyperexponential_distribution<RealT,PolicyT> const& dist = c.dist; | ||
|  | 
 | ||
|  |     return hyperexp_detail::quantile_impl(dist, p , true); | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT mean(hyperexponential_distribution<RealT, PolicyT> const& dist) | ||
|  | { | ||
|  |     RealT result = 0; | ||
|  | 
 | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         const exponential_distribution<RealT,PolicyT> exp(rates[i]); | ||
|  | 
 | ||
|  |         result += probs[i]*mean(exp); | ||
|  |     } | ||
|  | 
 | ||
|  |     return result; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT variance(hyperexponential_distribution<RealT, PolicyT> const& dist) | ||
|  | { | ||
|  |     RealT result = 0; | ||
|  | 
 | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         result += probs[i]/(rates[i]*rates[i]); | ||
|  |     } | ||
|  | 
 | ||
|  |     const RealT mean = boost::math::mean(dist); | ||
|  | 
 | ||
|  |     result = 2*result-mean*mean; | ||
|  | 
 | ||
|  |     return result; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT skewness(hyperexponential_distribution<RealT,PolicyT> const& dist) | ||
|  | { | ||
|  |     BOOST_MATH_STD_USING | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     RealT s1 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i} | ||
|  |     RealT s2 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i^2} | ||
|  |     RealT s3 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i^3} | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         const RealT p = probs[i]; | ||
|  |         const RealT r = rates[i]; | ||
|  |         const RealT r2 = r*r; | ||
|  |         const RealT r3 = r2*r; | ||
|  | 
 | ||
|  |         s1 += p/r; | ||
|  |         s2 += p/r2; | ||
|  |         s3 += p/r3; | ||
|  |     } | ||
|  | 
 | ||
|  |     const RealT s1s1 = s1*s1; | ||
|  | 
 | ||
|  |     const RealT num = (6*s3 - (3*(2*s2 - s1s1) + s1s1)*s1); | ||
|  |     const RealT den = (2*s2 - s1s1); | ||
|  | 
 | ||
|  |     return num / pow(den, static_cast<RealT>(1.5)); | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT kurtosis(hyperexponential_distribution<RealT,PolicyT> const& dist) | ||
|  | { | ||
|  |     const std::size_t n = dist.num_phases(); | ||
|  |     const std::vector<RealT> probs = dist.probabilities(); | ||
|  |     const std::vector<RealT> rates = dist.rates(); | ||
|  | 
 | ||
|  |     RealT s1 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i} | ||
|  |     RealT s2 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i^2} | ||
|  |     RealT s3 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i^3} | ||
|  |     RealT s4 = 0; // \sum_{i=1}^n \frac{p_i}{\lambda_i^4} | ||
|  |     for (std::size_t i = 0; i < n; ++i) | ||
|  |     { | ||
|  |         const RealT p = probs[i]; | ||
|  |         const RealT r = rates[i]; | ||
|  |         const RealT r2 = r*r; | ||
|  |         const RealT r3 = r2*r; | ||
|  |         const RealT r4 = r3*r; | ||
|  | 
 | ||
|  |         s1 += p/r; | ||
|  |         s2 += p/r2; | ||
|  |         s3 += p/r3; | ||
|  |         s4 += p/r4; | ||
|  |     } | ||
|  | 
 | ||
|  |     const RealT s1s1 = s1*s1; | ||
|  | 
 | ||
|  |     const RealT num = (24*s4 - 24*s3*s1 + 3*(2*(2*s2 - s1s1) + s1s1)*s1s1); | ||
|  |     const RealT den = (2*s2 - s1s1); | ||
|  | 
 | ||
|  |     return num/(den*den); | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT kurtosis_excess(hyperexponential_distribution<RealT,PolicyT> const& dist) | ||
|  | { | ||
|  |     return kurtosis(dist) - 3; | ||
|  | } | ||
|  | 
 | ||
|  | template <typename RealT, typename PolicyT> | ||
|  | RealT mode(hyperexponential_distribution<RealT,PolicyT> const& /*dist*/) | ||
|  | { | ||
|  |     return 0; | ||
|  | } | ||
|  | 
 | ||
|  | }} // namespace boost::math | ||
|  | 
 | ||
|  | #ifdef BOOST_MSVC | ||
|  | #pragma warning (pop) | ||
|  | #endif | ||
|  | // This include must be at the end, *after* the accessors | ||
|  | // for this distribution have been defined, in order to | ||
|  | // keep compilers that support two-phase lookup happy. | ||
|  | #include <boost/math/distributions/detail/derived_accessors.hpp> | ||
|  | #include <boost/math/distributions/detail/generic_quantile.hpp> | ||
|  | 
 | ||
|  | #endif // BOOST_MATH_DISTRIBUTIONS_HYPEREXPONENTIAL |