ImpactX
KVdist.H
Go to the documentation of this file.
1 /* Copyright 2022-2023 The Regents of the University of California, through Lawrence
2  * Berkeley National Laboratory (subject to receipt of any required
3  * approvals from the U.S. Dept. of Energy). All rights reserved.
4  *
5  * This file is part of ImpactX.
6  *
7  * Authors: Chad Mitchell, Axel Huebl
8  * License: BSD-3-Clause-LBNL
9  */
10 #ifndef IMPACTX_DISTRIBUTION_KVDIST
11 #define IMPACTX_DISTRIBUTION_KVDIST
12 
13 #include <AMReX_Random.H>
14 #include <AMReX_REAL.H>
15 
16 #include <cmath>
17 
18 
19 namespace impactx
20 {
21 namespace distribution
22 {
23  struct KVdist
24  {
35  KVdist(amrex::ParticleReal const sigx, amrex::ParticleReal const sigy,
36  amrex::ParticleReal const sigt,amrex::ParticleReal const sigpx,
37  amrex::ParticleReal const sigpy,amrex::ParticleReal const sigpt,
38  amrex::ParticleReal const muxpx=0.0, amrex::ParticleReal const muypy=0.0,
39  amrex::ParticleReal const mutpt=0.0
40  )
41  : m_sigmaX(sigx),m_sigmaY(sigy),m_sigmaT(sigt),m_sigmaPx(sigpx),m_sigmaPy(sigpy),
42  m_sigmaPt(sigpt),m_muxpx(muxpx),m_muypy(muypy),m_mutpt(mutpt)
43  {
44  }
45 
58  amrex::ParticleReal & x,
59  amrex::ParticleReal & y,
60  amrex::ParticleReal & t,
61  amrex::ParticleReal & px,
62  amrex::ParticleReal & py,
63  amrex::ParticleReal & pt,
64  amrex::RandomEngine const& engine) const {
65 
66  using namespace amrex::literals;
67 
68  amrex::ParticleReal v,phi,r,beta,p,u1,u2,ln1;
69  amrex::ParticleReal root,a1,a2;
70 
71  constexpr amrex::ParticleReal pi = 3.14159265358979_prt;
72 
73  // Sample and transform to define (x,y):
74  v = amrex::Random(engine);
75  phi = amrex::Random(engine);
76  phi = 2_prt*pi*phi;
77  r = sqrt(v);
78  x = r*cos(phi);
79  y = r*sin(phi);
80 
81  // Sample and transform to define (px,py):
82  beta = amrex::Random(engine);
83  beta = 2_prt*pi*beta;
84  p = sqrt(1_prt-pow(r,2));
85  px = p*cos(beta);
86  py = p*sin(beta);
87 
88  // Sample and transform to define (t,pt):
89  t = amrex::Random(engine);
90  t = 2.0_prt*(t-0.5_prt);
91  u1 = amrex::Random(engine);
92  u2 = amrex::Random(engine);
93  ln1 = sqrt(-2_prt*log(u1));
94  pt = ln1*cos(2_prt*pi*u2);
95 
96  // Scale to produce the identity covariance matrix:
97  amrex::ParticleReal c = sqrt(3.0_prt);
98  x = 2_prt*x;
99  y = 2_prt*y;
100  t = c*t;
101  px = 2_prt*px;
102  py = 2_prt*py;
103  // pt = pt;
104 
105  // Transform to produce the desired second moments/correlations:
106  root = sqrt(1.0_prt-m_muxpx*m_muxpx);
107  a1 = m_sigmaX*x/root;
108  a2 = m_sigmaPx*(-m_muxpx*x/root+px);
109  x = a1;
110  px = a2;
111  root = sqrt(1.0_prt-m_muypy*m_muypy);
112  a1 = m_sigmaY*y/root;
113  a2 = m_sigmaPy*(-m_muypy*y/root+py);
114  y = a1;
115  py = a2;
116  root = sqrt(1.0_prt-m_mutpt*m_mutpt);
117  a1 = m_sigmaT*t/root;
118  a2 = m_sigmaPt*(-m_mutpt*t/root+pt);
119  t = a1;
120  pt = a2;
121  }
122  private:
123  amrex::ParticleReal m_sigmaX,m_sigmaY,m_sigmaT;
124  amrex::ParticleReal m_sigmaPx,m_sigmaPy,m_sigmaPt;
125  amrex::ParticleReal m_muxpx,m_muypy,m_mutpt;
126  };
127 
128 } // namespace distribution
129 } // namespace impactx
130 
131 #endif // IMPACTX_DISTRIBUTION_KVDIST
Definition: KVdist.H:23
amrex::ParticleReal m_sigmaPy
Definition: KVdist.H:124
constexpr std::enable_if_t< std::is_floating_point< T >::value, T > pi()
KVdist(amrex::ParticleReal const sigx, amrex::ParticleReal const sigy, amrex::ParticleReal const sigt, amrex::ParticleReal const sigpx, amrex::ParticleReal const sigpy, amrex::ParticleReal const sigpt, amrex::ParticleReal const muxpx=0.0, amrex::ParticleReal const muypy=0.0, amrex::ParticleReal const mutpt=0.0)
Definition: KVdist.H:35
Definition: ImpactX.cpp:31
Real Random()
amrex::ParticleReal m_sigmaPx
related RMS sizes (length)
Definition: KVdist.H:124
c
#define AMREX_FORCE_INLINE
#define AMREX_GPU_HOST_DEVICE
amrex::ParticleReal m_mutpt
Definition: KVdist.H:125
amrex::ParticleReal m_muxpx
RMS momentum.
Definition: KVdist.H:125
amrex::ParticleReal m_sigmaX
Definition: KVdist.H:123
amrex::ParticleReal m_muypy
Definition: KVdist.H:125
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE GpuComplex< T > log(const GpuComplex< T > &a_z) noexcept
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE GpuComplex< T > pow(const GpuComplex< T > &a_z, const T &a_y) noexcept
amrex::ParticleReal m_sigmaT
Definition: KVdist.H:123
amrex::ParticleReal m_sigmaY
Definition: KVdist.H:123
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE void operator()(amrex::ParticleReal &x, amrex::ParticleReal &y, amrex::ParticleReal &t, amrex::ParticleReal &px, amrex::ParticleReal &py, amrex::ParticleReal &pt, amrex::RandomEngine const &engine) const
Definition: KVdist.H:57
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE GpuComplex< T > sqrt(const GpuComplex< T > &a_z) noexcept
amrex::ParticleReal m_sigmaPt
Definition: KVdist.H:124