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LandauDistribution.hpp
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1 // This file is part of the Acts project.
2 //
3 // Copyright (C) 2018-2020 CERN for the benefit of the Acts project
4 //
5 // This Source Code Form is subject to the terms of the Mozilla Public
6 // License, v. 2.0. If a copy of the MPL was not distributed with this
7 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 
9 #pragma once
10 
11 #include <random>
12 
13 namespace ActsFatras {
14 
19  public:
21  struct param_type {
24 
28  double location = 0.0;
30  double scale = 1.0;
31 
33  param_type(double location_, double scale_)
34  : location(location_), scale(scale_) {}
35  // Explicitlely defaulted construction and assignment
36  param_type() = default;
37  param_type(const param_type &) = default;
38  param_type(param_type &&) = default;
39  param_type &operator=(const param_type &) = default;
40  param_type &operator=(param_type &&) = default;
41 
43  friend bool operator==(const param_type &lhs, const param_type &rhs) {
44  return (lhs.location == rhs.location) and (lhs.scale == rhs.scale);
45  }
46  friend bool operator!=(const param_type &lhs, const param_type &rhs) {
47  return not(lhs == rhs);
48  }
49  };
51  using result_type = double;
52 
54  LandauDistribution(double location, double scale) : m_cfg(location, scale) {}
56  LandauDistribution(const param_type &cfg) : m_cfg(cfg) {}
57  // Explicitlely defaulted construction and assignment
58  LandauDistribution() = default;
59  LandauDistribution(const LandauDistribution &) = default;
63 
65  void reset() {}
67  param_type param() const { return m_cfg; }
69  void param(const param_type &cfg) { m_cfg = cfg; }
70 
72  result_type min() const { return -std::numeric_limits<double>::infinity(); }
74  result_type max() const { return std::numeric_limits<double>::infinity(); }
75 
77  template <typename Generator>
79  return (*this)(generator, m_cfg);
80  }
82  template <typename Generator>
84  const auto z = std::uniform_real_distribution<double>()(generator);
85  return params.location + params.scale * quantile(z);
86  }
87 
89  friend bool operator==(const LandauDistribution &lhs,
90  const LandauDistribution &rhs) {
91  return lhs.m_cfg == rhs.m_cfg;
92  }
93  friend bool operator!=(const LandauDistribution &lhs,
94  const LandauDistribution &rhs) {
95  return !(lhs == rhs);
96  }
97 
98  private:
100 
101  static double quantile(double z);
102 };
103 
104 } // namespace ActsFatras