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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/BernoulliDistribution.hh 0006 //---------------------------------------------------------------------------// 0007 #pragma once 0008 0009 #include "corecel/Assert.hh" 0010 #include "corecel/Macros.hh" 0011 #include "corecel/Types.hh" 0012 0013 #include "GenerateCanonical.hh" 0014 0015 namespace celeritas 0016 { 0017 //---------------------------------------------------------------------------// 0018 /*! 0019 * Select one of two options with a given probability. 0020 * 0021 * The constructor argument is the chance of returning `true`, with an optional 0022 * second argument for normalizing with a fraction of `false` values. 0023 * \code 0024 BernoulliDistribution snake_eyes(1, 35); 0025 if (snake_eyes(rng)) 0026 { 0027 // ... 0028 } 0029 BernoulliDistribution also_snake_eyes(1.0 / 36.0); 0030 \endcode 0031 */ 0032 class BernoulliDistribution 0033 { 0034 public: 0035 //!@{ 0036 //! \name Type aliases 0037 using result_type = bool; 0038 //!@} 0039 0040 public: 0041 // Construct with the probability of returning true 0042 explicit inline CELER_FUNCTION BernoulliDistribution(real_type p_true); 0043 0044 // Construct with the UNnormalized probability of returning true or false 0045 inline CELER_FUNCTION 0046 BernoulliDistribution(real_type scaled_true, real_type scaled_false); 0047 0048 // Sample true or false based on the probability 0049 template<class Generator> 0050 inline CELER_FUNCTION result_type operator()(Generator& rng) const; 0051 0052 //! Probability of returning `true` from operator() 0053 real_type p() const { return p_true_; } 0054 0055 private: 0056 real_type p_true_; 0057 }; 0058 0059 //---------------------------------------------------------------------------// 0060 // INLINE DEFINITIONS 0061 //---------------------------------------------------------------------------// 0062 /*! 0063 * Construct with the probability of returning true. 0064 */ 0065 CELER_FUNCTION BernoulliDistribution::BernoulliDistribution(real_type p_true) 0066 : p_true_(p_true) 0067 { 0068 CELER_EXPECT(p_true >= 0 && p_true <= 1); 0069 } 0070 0071 //---------------------------------------------------------------------------// 0072 /*! 0073 * Construct with the UNnormalized probability of returning true or false 0074 */ 0075 CELER_FUNCTION 0076 BernoulliDistribution::BernoulliDistribution(real_type scaled_true, 0077 real_type scaled_false) 0078 : p_true_(scaled_true / (scaled_true + scaled_false)) 0079 { 0080 CELER_EXPECT(scaled_true > 0 || scaled_false > 0); 0081 CELER_EXPECT(scaled_true >= 0 && scaled_false >= 0); 0082 } 0083 0084 //---------------------------------------------------------------------------// 0085 /*! 0086 * Construct with the probability of returning true. 0087 */ 0088 template<class Generator> 0089 CELER_FUNCTION auto 0090 BernoulliDistribution::operator()(Generator& rng) const -> result_type 0091 { 0092 return generate_canonical<real_type>(rng) < p_true_; 0093 } 0094 0095 //---------------------------------------------------------------------------// 0096 } // namespace celeritas
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