ConstF.H

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/* Copyright 2022-2023 The Regents of the University of California, through Lawrence
 *           Berkeley National Laboratory (subject to receipt of any required
 *           approvals from the U.S. Dept. of Energy). All rights reserved.
 *
 * This file is part of ImpactX.
 *
 * Authors: Chad Mitchell, Axel Huebl
 * License: BSD-3-Clause-LBNL
 */
#ifndef IMPACTX_CONSTF_H
#define IMPACTX_CONSTF_H
 
#include "particles/ImpactXParticleContainer.H"
#include "mixin/alignment.H"
#include "mixin/pipeaperture.H"
#include "mixin/beamoptic.H"
#include "mixin/thick.H"
#include "mixin/lineartransport.H"
#include "mixin/named.H"
#include "mixin/nofinalize.H"
 
#include <AMReX_Extension.H>
#include <AMReX_Math.H>
#include <AMReX_REAL.H>
#include <AMReX_SIMD.H>
 
#include <cmath>
#include <stdexcept>
 
 
namespace impactx::elements
{
    struct ConstF
    : public mixin::Named,
      public mixin::BeamOptic<ConstF>,
      public mixin::LinearTransport<ConstF>,
      public mixin::Thick,
      public mixin::Alignment,
      public mixin::PipeAperture,
      public mixin::NoFinalize,
      public amrex::simd::Vectorized<amrex::simd::native_simd_size_particlereal>
    {
        static constexpr auto type = "ConstF";
        using PType = ImpactXParticleContainer::ParticleType;

        ConstF (
            amrex::ParticleReal ds,
            amrex::ParticleReal kx,
            amrex::ParticleReal ky,
            amrex::ParticleReal kt,
            amrex::ParticleReal dx = 0,
            amrex::ParticleReal dy = 0,
            amrex::ParticleReal rotation_degree = 0,
            amrex::ParticleReal aperture_x = 0,
            amrex::ParticleReal aperture_y = 0,
            int nslice = 1,
            std::optional<std::string> name = std::nullopt
        )
        : Named(std::move(name)),
          Thick(ds, nslice),
          Alignment(dx, dy, rotation_degree),
          PipeAperture(aperture_x, aperture_y),
          m_kx(kx), m_ky(ky), m_kt(kt)
        {
        }

        using BeamOptic::operator();

        void compute_constants (RefPart const & refpart)
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            Alignment::compute_constants(refpart);
 
            // length of the current slice
            amrex::ParticleReal const slice_ds = m_ds / nslice();
 
            // find beta*gamma^2
            amrex::ParticleReal const betgam2 = powi<2>(refpart.pt) - 1.0_prt;
 
            // trigo
            auto const [sin_kxds, cos_kxds] = amrex::Math::sincos(m_kx * slice_ds);
            m_cos_kxds = cos_kxds;
            m_const_x = -m_kx * sin_kxds;
            auto const [sin_kyds, cos_kyds] = amrex::Math::sincos(m_ky * slice_ds);
            m_cos_kyds = cos_kyds;
            m_const_y = -m_ky * sin_kyds;
            auto const [sin_ktds, cos_ktds] = amrex::Math::sincos(m_kt * slice_ds);
            m_cos_ktds = cos_ktds;
            m_const_t = -m_kt * betgam2 * sin_ktds;
 
            // intermediate quantities - to avoid division by zero
            m_sincx = m_kx > 0 ? std::sin(m_kx * slice_ds) / m_kx : slice_ds;
            m_sincy = m_ky > 0 ? std::sin(m_ky * slice_ds) / m_ky : slice_ds;
            amrex::ParticleReal const sinct = m_kt > 0 ? std::sin(m_kt * slice_ds) / m_kt : slice_ds;
            m_const_pt = sinct / betgam2;
        }

        template<typename T_Real=amrex::ParticleReal, typename T_IdCpu=uint64_t>
        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        void operator() (
            T_Real & AMREX_RESTRICT x,
            T_Real & AMREX_RESTRICT y,
            T_Real & AMREX_RESTRICT t,
            T_Real & AMREX_RESTRICT px,
            T_Real & AMREX_RESTRICT py,
            T_Real & AMREX_RESTRICT pt,
            T_IdCpu & AMREX_RESTRICT idcpu,
            [[maybe_unused]] RefPart const & AMREX_RESTRICT refpart
        ) const
        {
            using namespace amrex::literals; // for _rt and _prt
 
            // shift due to alignment errors of the element
            shift_in(x, y, px, py);
 
            // initialize output values
            T_Real xout = x;
            T_Real yout = y;
            T_Real tout = t;
            T_Real pxout = px;
            T_Real pyout = py;
            T_Real ptout = pt;
 
            // advance position and momentum
            xout = m_cos_kxds * x + m_sincx    * px;
            pxout = m_const_x * x + m_cos_kxds * px;
 
            yout = m_cos_kyds * y + m_sincy    * py;
            pyout = m_const_y * y + m_cos_kyds * py;
 
            tout = m_cos_ktds * t + m_const_pt * pt;
            ptout = m_const_t * t + m_cos_ktds * pt;
 
            // assign updated values
            x = xout;
            y = yout;
            t = tout;
            px = pxout;
            py = pyout;
            pt = ptout;
 
            // apply transverse aperture
            apply_aperture(x, y, idcpu);
 
            // undo shift due to alignment errors of the element
            shift_out(x, y, px, py);
        }

        AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
        void operator() (RefPart & AMREX_RESTRICT refpart) const {
 
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            // assign input reference particle values
            amrex::ParticleReal const x = refpart.x;
            amrex::ParticleReal const px = refpart.px;
            amrex::ParticleReal const y = refpart.y;
            amrex::ParticleReal const py = refpart.py;
            amrex::ParticleReal const z = refpart.z;
            amrex::ParticleReal const pz = refpart.pz;
            amrex::ParticleReal const t = refpart.t;
            amrex::ParticleReal const pt = refpart.pt;
            amrex::ParticleReal const s = refpart.s;
 
            // length of the current slice
            amrex::ParticleReal const slice_ds = m_ds / nslice();
 
            // assign intermediate parameter
            amrex::ParticleReal const step = slice_ds / std::sqrt(powi<2>(pt) - 1.0_prt);
 
            // advance position and momentum (straight element)
            refpart.x = x + step*px;
            refpart.y = y + step*py;
            refpart.z = z + step*pz;
            refpart.t = t - step*pt;
 
            // advance integrated path length
            refpart.s = s + slice_ds;
 
        }

        using LinearTransport::operator();

        AMREX_GPU_HOST AMREX_FORCE_INLINE
        Map6x6
        transport_map ([[maybe_unused]] RefPart const & AMREX_RESTRICT refpart) const
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
 
            // length of the current slice
            amrex::ParticleReal const slice_ds = m_ds / nslice();
 
            // find beta*gamma^2
            amrex::ParticleReal const betgam2 = powi<2>(refpart.pt) - 1.0_prt;
 
            // trigo
            auto const [sin_kxds, cos_kxds] = amrex::Math::sincos(m_kx * slice_ds);
            amrex::ParticleReal const_x = -m_kx * sin_kxds;
            auto const [sin_kyds, cos_kyds] = amrex::Math::sincos(m_ky * slice_ds);
            amrex::ParticleReal const_y = -m_ky * sin_kyds;
            auto const [sin_ktds, cos_ktds] = amrex::Math::sincos(m_kt * slice_ds);
            amrex::ParticleReal const_t = -m_kt * betgam2 * sin_ktds;
 
            // intermediate quantities - to avoid division by zero
            amrex::ParticleReal sincx = m_kx > 0 ? std::sin(m_kx * slice_ds) / m_kx : slice_ds;
            amrex::ParticleReal sincy = m_ky > 0 ? std::sin(m_ky * slice_ds) / m_ky : slice_ds;
            amrex::ParticleReal const sinct = m_kt > 0 ? std::sin(m_kt * slice_ds) / m_kt : slice_ds;
            amrex::ParticleReal const_pt = sinct / betgam2;
 
            // assign linear map matrix elements
            Map6x6 R = Map6x6::Identity();
            R(1,1) = cos_kxds;
            R(1,2) = sincx;
            R(2,1) = const_x;
            R(2,2) = cos_kxds;
            R(3,3) = cos_kyds;
            R(3,4) = sincy;
            R(4,3) = const_y;
            R(4,4) = cos_kyds;
            R(5,5) = cos_ktds;
            R(5,6) = const_pt;
            R(6,5) = const_t;
            R(6,6) = cos_ktds;
 
            return R;
        }
 
        amrex::ParticleReal m_kx; 
        amrex::ParticleReal m_ky; 
        amrex::ParticleReal m_kt; 
 
      private:
        // constants that are independent of the individually tracked particle,
        // see: compute_constants() to refresh
        amrex::ParticleReal m_sincx, m_sincy;
        amrex::ParticleReal m_const_x, m_const_y, m_const_t, m_const_pt;
        amrex::ParticleReal m_cos_kxds, m_cos_kyds, m_cos_ktds;
    };
 
} // namespace impactx
 
#endif // IMPACTX_CONSTF_H