QEDPairGeneration.H

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/* Copyright 2019 Luca Fedeli
 *
 * This file is part of WarpX.
 *
 * License: BSD-3-Clause-LBNL
 */

#ifndef QED_PAIR_GENERATION_H_
#define QED_PAIR_GENERATION_H_

#include "Particles/Gather/FieldGather.H"
#include "Particles/Gather/GetExternalFields.H"
#include "Particles/Pusher/GetAndSetPosition.H"
#include "Particles/WarpXParticleContainer.H"
#include "QEDInternals/BreitWheelerEngineWrapper.H"

#include <AMReX_Array.H>
#include <AMReX_Array4.H>
#include <AMReX_Dim3.H>
#include <AMReX_Extension.H>
#include <AMReX_GpuQualifiers.H>
#include <AMReX_IndexType.H>
#include <AMReX_REAL.H>

#include <AMReX_BaseFwd.H>

class PairGenerationFilterFunc
{
public:

    PairGenerationFilterFunc(int const opt_depth_runtime_comp)
        : m_opt_depth_runtime_comp(opt_depth_runtime_comp)
        {}

    template <typename PData>
    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    bool operator() (const PData& ptd, int const i, amrex::RandomEngine const&) const noexcept
    {
        using namespace amrex;

        const amrex::ParticleReal opt_depth =
            ptd.m_runtime_rdata[m_opt_depth_runtime_comp][i];
        return (opt_depth < 0.0_rt);
    }

private:
    int m_opt_depth_runtime_comp = 0; 
};

class PairGenerationTransformFunc
{
public:

    PairGenerationTransformFunc(BreitWheelerGeneratePairs const generate_functor,
                                const WarpXParIter& a_pti, int lev, amrex::IntVect ngE,
                                amrex::FArrayBox const& exfab,
                                amrex::FArrayBox const& eyfab,
                                amrex::FArrayBox const& ezfab,
                                amrex::FArrayBox const& bxfab,
                                amrex::FArrayBox const& byfab,
                                amrex::FArrayBox const& bzfab,
                                amrex::Array<amrex::Real,3> v_galilean,
                                int a_offset = 0);

    template <typename DstData, typename SrcData>
    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
    void operator() (DstData& dst1, DstData& dst2, SrcData& src,
        int const i_src, int const i_dst1, int const i_dst2,
        amrex::RandomEngine const& engine) const noexcept
    {
        using namespace amrex;

        // gather E and B
        amrex::ParticleReal xp, yp, zp;
        m_get_position(i_src, xp, yp, zp);

        amrex::ParticleReal ex = 0._rt, ey = 0._rt, ez = 0._rt;
        m_get_externalE(i_src, ex, ey, ez);

        amrex::ParticleReal bx = 0._rt, by = 0._rt, bz = 0._rt;
        m_get_externalB(i_src, bx, by, bz);

        doGatherShapeN(xp, yp, zp, ex, ey, ez, bx, by, bz,
                       m_ex_arr, m_ey_arr, m_ez_arr, m_bx_arr, m_by_arr, m_bz_arr,
                       m_ex_type, m_ey_type, m_ez_type, m_bx_type, m_by_type, m_bz_type,
                       m_dx_arr, m_xyzmin_arr, m_lo, m_n_rz_azimuthal_modes,
                       m_nox, m_galerkin_interpolation);

        //Despite the names of the variables, positrons and electrons
        //can be exchanged, since the physical process is completely
        //symmetric with respect to this exchange.
        const auto& ux = src.m_rdata[PIdx::ux][i_src];
        const auto& uy = src.m_rdata[PIdx::uy][i_src];
        const auto& uz = src.m_rdata[PIdx::uz][i_src];
        auto& e_ux = dst1.m_rdata[PIdx::ux][i_dst1];
        auto& e_uy = dst1.m_rdata[PIdx::uy][i_dst1];
        auto& e_uz = dst1.m_rdata[PIdx::uz][i_dst1];
        auto& p_ux = dst2.m_rdata[PIdx::ux][i_dst2];
        auto& p_uy = dst2.m_rdata[PIdx::uy][i_dst2];
        auto& p_uz = dst2.m_rdata[PIdx::uz][i_dst2];
        m_generate_functor(
            ux, uy, uz,
            ex, ey, ez,
            bx, by, bz,
            e_ux, e_uy, e_uz,
            p_ux, p_uy, p_uz,
            engine);

        src.m_aos[i_src].id() = -1; //destroy photon after pair generation
    }

private:

    const BreitWheelerGeneratePairs
    m_generate_functor; 
    GetParticlePosition m_get_position;
    GetExternalEField m_get_externalE;
    GetExternalBField m_get_externalB;

    amrex::Array4<const amrex::Real> m_ex_arr;
    amrex::Array4<const amrex::Real> m_ey_arr;
    amrex::Array4<const amrex::Real> m_ez_arr;
    amrex::Array4<const amrex::Real> m_bx_arr;
    amrex::Array4<const amrex::Real> m_by_arr;
    amrex::Array4<const amrex::Real> m_bz_arr;

    amrex::IndexType m_ex_type;
    amrex::IndexType m_ey_type;
    amrex::IndexType m_ez_type;
    amrex::IndexType m_bx_type;
    amrex::IndexType m_by_type;
    amrex::IndexType m_bz_type;

    amrex::GpuArray<amrex::Real, 3> m_dx_arr;
    amrex::GpuArray<amrex::Real, 3> m_xyzmin_arr;

    bool m_galerkin_interpolation;
    int m_nox;
    int m_n_rz_azimuthal_modes;

    amrex::Dim3 m_lo;
};

#endif //QED_PAIR_GENERATION_H_