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File indexing completed on 2025-09-14 08:50:58
0001 //------------------------------- -*- C++ -*- -------------------------------// 0002 // Copyright Celeritas contributors: see top-level COPYRIGHT file for details 0003 // SPDX-License-Identifier: (Apache-2.0 OR MIT) 0004 //---------------------------------------------------------------------------// 0005 //! \file corecel/random/distribution/GenerateCanonical.hh 0006 //---------------------------------------------------------------------------// 0007 #pragma once 0008 0009 #include <limits> 0010 #include <random> 0011 #include <type_traits> 0012 0013 #include "corecel/Macros.hh" 0014 #include "corecel/Types.hh" 0015 0016 namespace celeritas 0017 { 0018 //---------------------------------------------------------------------------// 0019 //! Helper function to generate a random uniform number 0020 template<class RealType, class Generator> 0021 inline CELER_FUNCTION RealType generate_canonical(Generator& g); 0022 0023 //---------------------------------------------------------------------------// 0024 //! Sample a real_type on [0, 1). 0025 template<class Generator> 0026 inline CELER_FUNCTION real_type generate_canonical(Generator& g); 0027 0028 //---------------------------------------------------------------------------// 0029 //! Implementation of each GenerateCanonical, used for CachedRngEngine 0030 enum class GenerateCanonicalPolicy 0031 { 0032 std, //!< Use standard library 0033 builtin32, //!< Use detail::GenerateCanonical32 0034 builtin64, //!< Use detail::GenerateCanonical64 (not yet implemented) 0035 custom, //!< Custom method 0036 size_ 0037 }; 0038 0039 //---------------------------------------------------------------------------// 0040 /*! 0041 * Generate random numbers in [0, 1). 0042 * 0043 * This is essentially an implementation detail; partial specialization can be 0044 * used to sample using special functions with a given generator. 0045 * 0046 * \todo For 1.0 refactor so that if RNGs have a builtin policy we call our 0047 * builtin functions; if they have a custom we call a function on the RNG 0048 * itself; and if they don't define a policy (e.g. a standard library 0049 * one) we fall back to calling std::generate_canonical. 0050 */ 0051 template<class Generator, class RealType = ::celeritas::real_type> 0052 struct GenerateCanonical 0053 { 0054 static_assert(std::is_floating_point<RealType>::value, 0055 "RealType must be float or double"); 0056 0057 //!@{ 0058 //! \name Type aliases 0059 using real_type = RealType; 0060 using result_type = real_type; 0061 //!@} 0062 0063 //! By default use standard library 0064 static constexpr auto policy = GenerateCanonicalPolicy::std; 0065 0066 // Sample a random number 0067 inline result_type operator()(Generator& rng); 0068 }; 0069 0070 //---------------------------------------------------------------------------// 0071 // INLINE DEFINITIONS 0072 //---------------------------------------------------------------------------// 0073 /*! 0074 * Generate random numbers in [0, 1). 0075 * 0076 * This is the default implementation, for CPU-only code. 0077 */ 0078 template<class Generator, class RealType> 0079 auto GenerateCanonical<Generator, RealType>::operator()(Generator& rng) 0080 -> result_type 0081 { 0082 using limits_t = std::numeric_limits<result_type>; 0083 return std::generate_canonical<result_type, limits_t::digits>(rng); 0084 } 0085 0086 //---------------------------------------------------------------------------// 0087 /*! 0088 * Helper function to generate a random real number in [0, 1). 0089 */ 0090 template<class RealType, class Generator> 0091 CELER_FUNCTION RealType generate_canonical(Generator& g) 0092 { 0093 return GenerateCanonical<Generator, RealType>()(g); 0094 } 0095 0096 //---------------------------------------------------------------------------// 0097 /*! 0098 * Helper function to generate a random real number in [0, 1). 0099 */ 0100 template<class Generator> 0101 CELER_FUNCTION real_type generate_canonical(Generator& g) 0102 { 0103 return GenerateCanonical<Generator, real_type>()(g); 0104 } 0105 0106 //---------------------------------------------------------------------------// 0107 } // namespace celeritas
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