ImpactX
ToFixedT.H
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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_TO_FIXED_T_H
11 #define IMPACTX_TO_FIXED_T_H
12 
14 
15 #include <AMReX_GpuQualifiers.H>
16 #include <AMReX_Math.H>
17 #include <AMReX_REAL.H>
18 
19 #include <cmath>
20 
21 
23 {
24  struct ToFixedT
25  {
27 
35  ToFixedT (amrex::ParticleReal const ptd)
36  : m_ptd(ptd)
37  {
38  }
39 
52  amrex::ParticleReal & x,
53  amrex::ParticleReal & y,
54  amrex::ParticleReal & t,
55  amrex::ParticleReal & px,
56  amrex::ParticleReal & py,
57  amrex::ParticleReal & pt) const
58  {
59  using namespace amrex::literals;
60 
61  // small tolerance to avoid NaN for pz<0:
62  constexpr amrex::ParticleReal tol = 1.0e-8_prt;
63 
64  // compute value of reference pzd = beta*gamma
65  amrex::ParticleReal const argd = -1.0_prt + pow(m_ptd, 2);
66  // AMREX_ASSERT_WITH_MESSAGE(argd > 0.0_prt, "invalid pzd arg (<=0)");
67  amrex::ParticleReal const pzdf = argd > 0.0_prt ? sqrt(argd) : tol;
68 
69  // transform momenta to dynamic units (eg, so that momenta are
70  // normalized by mc):
71  px = px * pzdf;
72  py = py * pzdf;
73  pt = pt * pzdf;
74 
75  // compute value of particle pz = beta*gamma
76  amrex::ParticleReal const arg = -1.0_prt + pow(m_ptd+pt, 2) - pow(px, 2) - pow(py, 2);
77  // AMREX_ASSERT_WITH_MESSAGE(arg > 0.0_prt, "invalid pz arg (<=0)");
78  amrex::ParticleReal const pzf = arg > 0.0_prt ? sqrt(arg) : tol;
79 
80  // transform position and momentum (from fixed s to fixed t)
81  x = x + px*t/(m_ptd+pt);
82  // px = px;
83  y = y + py*t/(m_ptd+pt);
84  // py = py;
85  auto & z = t; // We store z in the same memory slot as t.
86  z = pzf * t / (m_ptd + pt);
87  auto & pz = pt; // We store pz in the same memory slot as pt.
88  pz = pzf - pzdf;
89 
90  // transform momenta to static units (eg, so that momenta are
91  // normalized by pzdf):
92  px = px / pzdf;
93  py = py / pzdf;
94  pz = pz / pzdf;
95  }
96 
97  private:
98  amrex::ParticleReal m_ptd;
99  };
100 
101 } // namespace impactx::transformation
102 
103 #endif // IMPACTX_TO_FIXED_T_H
#define AMREX_FORCE_INLINE
#define AMREX_GPU_HOST_DEVICE
AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE T arg(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_GPU_HOST_DEVICE AMREX_FORCE_INLINE GpuComplex< T > sqrt(const GpuComplex< T > &a_z) noexcept
Definition: CoordinateTransformation.cpp:23
@ t
fixed t as the independent variable
Definition: ToFixedT.H:25
ToFixedT(amrex::ParticleReal const ptd)
Definition: ToFixedT.H:35
amrex::ParticleReal m_ptd
Design value of pt/mc2 = -gamma.
Definition: ToFixedT.H:98
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) const
Definition: ToFixedT.H:51
ImpactXParticleContainer::ParticleType PType
Definition: ToFixedT.H:26