TaperedPL.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_TAPEREDPL_H
#define IMPACTX_TAPEREDPL_H
 
#include "particles/ImpactXParticleContainer.H"
#include "mixin/alignment.H"
#include "mixin/beamoptic.H"
#include "mixin/thin.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 TaperedPL
    : public mixin::Named,
      public mixin::BeamOptic<TaperedPL>,
      public mixin::LinearTransport<TaperedPL>,
      public mixin::Thin,
      public mixin::Alignment,
      public mixin::NoFinalize
      // At least on Intel AVX512, there is a small overhead to vectorize this element, see
      // https://github.com/BLAST-ImpactX/impactx/pull/1002
      // public amrex::simd::Vectorized<amrex::simd::native_simd_size_particlereal>
    {
        static constexpr auto type = "TaperedPL";
        using PType = ImpactXParticleContainer::ParticleType;

        TaperedPL (
            amrex::ParticleReal k,
            amrex::ParticleReal taper,
            int unit,
            amrex::ParticleReal dx = 0,
            amrex::ParticleReal dy = 0,
            amrex::ParticleReal rotation_degree = 0,
            std::optional<std::string> name = std::nullopt
        )
        : Named(std::move(name)),
          Alignment(dx, dy, rotation_degree),
          m_k(k), m_taper(taper), m_unit(unit)
        {
        }

        using BeamOptic::operator();

        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,
            [[maybe_unused]] T_IdCpu & AMREX_RESTRICT idcpu,
            RefPart const & AMREX_RESTRICT refpart
        ) const
        {
            using namespace amrex::literals; // for _rt and _prt
            using amrex::Math::powi;
            using namespace std; // for cmath(float)
 
            // shift due to alignment errors of the element
            shift_in(x, y, px, py);
 
            // normalize focusing strength units to MAD-X convention if needed
            amrex::ParticleReal g = m_k;
            if (m_unit == 1) {
                g = m_k / refpart.rigidity_Tm();
            }
 
            // 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 = x;
            pxout = px - g * ( x + m_taper*0.5_prt * (powi<2>(x) + powi<2>(y)) );
 
            yout = y;
            pyout = py - g * ( y + m_taper * x * y );
 
            tout = t;
            ptout = pt;
 
            // assign updated values
            x = xout;
            y = yout;
            t = tout;
            px = pxout;
            py = pyout;
            pt = ptout;
 
            // undo shift due to alignment errors of the element
            shift_out(x, y, px, py);
        }

        using Thin::operator();

        using LinearTransport::operator();

        AMREX_GPU_HOST AMREX_FORCE_INLINE
        Map6x6
        transport_map ([[maybe_unused]] RefPart const & AMREX_RESTRICT refpart) const
        {
            throw std::runtime_error(std::string(type) + ": Envelope tracking is not yet implemented!");
            return Map6x6::Identity();
        }
 
        amrex::ParticleReal m_k; 
        amrex::ParticleReal m_taper; 
        int m_unit;  
    };
 
} // namespace impactx
 
#endif // IMPACTX_TAPEREDPL_H