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256 lines
8.4 KiB
256 lines
8.4 KiB
/* |
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* Copyright 2008-2012 NVIDIA Corporation |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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/*! \file subtract_with_carry_engine.h |
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* \brief A subtract-with-carry pseudorandom number generator |
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* based on Marsaglia & Zaman. |
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*/ |
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#pragma once |
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#include <thrust/detail/config.h> |
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#include <thrust/random/detail/random_core_access.h> |
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#include <thrust/detail/cstdint.h> |
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#include <cstddef> // for size_t |
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#include <iostream> |
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namespace thrust |
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{ |
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namespace random |
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{ |
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/*! \addtogroup random_number_engine_templates |
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* \{ |
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*/ |
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/*! \class subtract_with_carry_engine |
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* \brief A \p subtract_with_carry_engine random number engine produces unsigned |
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* integer random numbers using the subtract with carry algorithm of Marsaglia & Zaman. |
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* |
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* The generation algorithm is performed as follows: |
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* -# Let <tt>Y = X_{i-s}- X_{i-r} - c</tt>. |
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* -# Set <tt>X_i</tt> to <tt>y = T mod m</tt>. Set \c c to \c 1 if <tt>Y < 0</tt>, otherwise set \c c to \c 0. |
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* |
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* This algorithm corresponds to a modular linear function of the form |
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* |
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* <tt>TA(x_i) = (a * x_i) mod b</tt>, where \c b is of the form <tt>m^r - m^s + 1</tt> and |
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* <tt>a = b - (b-1)/m</tt>. |
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* |
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* \tparam UIntType The type of unsigned integer to produce. |
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* \tparam w The word size of the produced values (<tt> w <= sizeof(UIntType)</tt>). |
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* \tparam s The short lag of the generation algorithm. |
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* \tparam r The long lag of the generation algorithm. |
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* |
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* \note Inexperienced users should not use this class template directly. Instead, use |
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* \p ranlux24_base or \p ranlux48_base, which are instances of \p subtract_with_carry_engine. |
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* |
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* \see thrust::random::ranlux24_base |
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* \see thrust::random::ranlux48_base |
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*/ |
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template<typename UIntType, size_t w, size_t s, size_t r> |
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class subtract_with_carry_engine |
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{ |
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/*! \cond |
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*/ |
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private: |
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static const UIntType modulus = UIntType(1) << w; |
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/*! \endcond |
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*/ |
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public: |
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// types |
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/*! \typedef result_type |
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* \brief The type of the unsigned integer produced by this \p subtract_with_carry_engine. |
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*/ |
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typedef UIntType result_type; |
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// engine characteristics |
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/*! The word size of the produced values. |
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*/ |
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static const size_t word_size = w; |
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/*! The size of the short lag used in the generation algorithm. |
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*/ |
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static const size_t short_lag = s; |
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/*! The size of the long lag used in the generation algorithm. |
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*/ |
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static const size_t long_lag = r; |
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/*! The smallest value this \p subtract_with_carry_engine may potentially produce. |
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*/ |
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static const result_type min = 0; |
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/*! The largest value this \p subtract_with_carry_engine may potentially produce. |
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*/ |
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static const result_type max = modulus - 1; |
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/*! The default seed of this \p subtract_with_carry_engine. |
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*/ |
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static const result_type default_seed = 19780503u; |
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// constructors and seeding functions |
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/*! This constructor, which optionally accepts a seed, initializes a new |
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* \p subtract_with_carry_engine. |
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* |
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* \param value The seed used to intialize this \p subtract_with_carry_engine's state. |
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*/ |
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__host__ __device__ |
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explicit subtract_with_carry_engine(result_type value = default_seed); |
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/*! This method initializes this \p subtract_with_carry_engine's state, and optionally accepts |
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* a seed value. |
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* |
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* \param value The seed used to initializes this \p subtract_with_carry_engine's state. |
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*/ |
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__host__ __device__ |
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void seed(result_type value = default_seed); |
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// generating functions |
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/*! This member function produces a new random value and updates this \p subtract_with_carry_engine's state. |
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* \return A new random number. |
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*/ |
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__host__ __device__ |
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result_type operator()(void); |
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/*! This member function advances this \p subtract_with_carry_engine's state a given number of times |
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* and discards the results. |
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* |
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* \param z The number of random values to discard. |
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* \note This function is provided because an implementation may be able to accelerate it. |
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*/ |
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__host__ __device__ |
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void discard(unsigned long long z); |
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/*! \cond |
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*/ |
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private: |
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result_type m_x[long_lag]; |
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unsigned int m_k; |
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int m_carry; |
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friend struct thrust::random::detail::random_core_access; |
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__host__ __device__ |
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bool equal(const subtract_with_carry_engine &rhs) const; |
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template<typename CharT, typename Traits> |
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std::basic_ostream<CharT,Traits>& stream_out(std::basic_ostream<CharT,Traits> &os) const; |
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template<typename CharT, typename Traits> |
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std::basic_istream<CharT,Traits>& stream_in(std::basic_istream<CharT,Traits> &is); |
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/*! \endcond |
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*/ |
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}; // end subtract_with_carry_engine |
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/*! This function checks two \p subtract_with_carry_engines for equality. |
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* \param lhs The first \p subtract_with_carry_engine to test. |
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* \param rhs The second \p subtract_with_carry_engine to test. |
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* \return \c true if \p lhs is equal to \p rhs; \c false, otherwise. |
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*/ |
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template<typename UIntType_, size_t w_, size_t s_, size_t r_> |
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__host__ __device__ |
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bool operator==(const subtract_with_carry_engine<UIntType_,w_,s_,r_> &lhs, |
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const subtract_with_carry_engine<UIntType_,w_,s_,r_> &rhs); |
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/*! This function checks two \p subtract_with_carry_engines for inequality. |
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* \param lhs The first \p subtract_with_carry_engine to test. |
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* \param rhs The second \p subtract_with_carry_engine to test. |
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* \return \c true if \p lhs is not equal to \p rhs; \c false, otherwise. |
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*/ |
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template<typename UIntType_, size_t w_, size_t s_, size_t r_> |
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__host__ __device__ |
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bool operator!=(const subtract_with_carry_engine<UIntType_,w_,s_,r_>&lhs, |
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const subtract_with_carry_engine<UIntType_,w_,s_,r_>&rhs); |
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/*! This function streams a subtract_with_carry_engine to a \p std::basic_ostream. |
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* \param os The \p basic_ostream to stream out to. |
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* \param e The \p subtract_with_carry_engine to stream out. |
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* \return \p os |
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*/ |
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template<typename UIntType_, size_t w_, size_t s_, size_t r_, |
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typename CharT, typename Traits> |
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std::basic_ostream<CharT,Traits>& |
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operator<<(std::basic_ostream<CharT,Traits> &os, |
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const subtract_with_carry_engine<UIntType_,w_,s_,r_> &e); |
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/*! This function streams a subtract_with_carry_engine in from a std::basic_istream. |
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* \param is The \p basic_istream to stream from. |
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* \param e The \p subtract_with_carry_engine to stream in. |
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* \return \p is |
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*/ |
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template<typename UIntType_, size_t w_, size_t s_, size_t r_, |
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typename CharT, typename Traits> |
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std::basic_istream<CharT,Traits>& |
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operator>>(std::basic_istream<CharT,Traits> &is, |
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subtract_with_carry_engine<UIntType_,w_,s_,r_> &e); |
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/*! \} // end random_number_engine_templates |
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*/ |
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/*! \addtogroup predefined_random |
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* \{ |
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*/ |
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// XXX N2111 uses uint_fast32_t here |
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/*! \typedef ranlux24_base |
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* \brief A random number engine with predefined parameters which implements the |
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* base engine of the \p ranlux24 random number engine. |
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* \note The 10000th consecutive invocation of a default-constructed object of type \p ranlux24_base |
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* shall produce the value \c 7937952 . |
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*/ |
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typedef subtract_with_carry_engine<thrust::detail::uint32_t, 24, 10, 24> ranlux24_base; |
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// XXX N2111 uses uint_fast64_t here |
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/*! \typedef ranlux48_base |
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* \brief A random number engine with predefined parameters which implements the |
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* base engine of the \p ranlux48 random number engine. |
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* \note The 10000th consecutive invocation of a default-constructed object of type \p ranlux48_base |
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* shall produce the value \c 192113843633948 . |
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*/ |
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typedef subtract_with_carry_engine<thrust::detail::uint64_t, 48, 5, 12> ranlux48_base; |
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/*! \} // end predefined_random |
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*/ |
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} // end random |
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// import names into thrust:: |
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using random::subtract_with_carry_engine; |
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using random::ranlux24_base; |
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using random::ranlux48_base; |
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} // end thrust |
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#include <thrust/random/detail/subtract_with_carry_engine.inl> |
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