HardEdged_K.H

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/* Copyright 2022 David Grote
 *
 * This file is part of WarpX.
 *
 * License: BSD-3-Clause-LBNL
 */
#ifndef WARPX_ACCELERATORLATTICE_LATTICEELEMENTS_HARDEDGED_K_H_
#define WARPX_ACCELERATORLATTICE_LATTICEELEMENTS_HARDEDGED_K_H_
 
#include "Utils/WarpXConst.H"
 
#include <AMReX_REAL.H>

AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
amrex::ParticleReal hard_edged_fraction(const amrex::ParticleReal z,
                                        const amrex::ParticleReal zpvdt,
                                        const amrex::ParticleReal zs,
                                        const amrex::ParticleReal ze)
{
 
    using namespace amrex::literals;
 
    // This allows vz to be positive or negative
    amrex::ParticleReal const zl = std::min(z, zpvdt);
    amrex::ParticleReal const zr = std::max(z, zpvdt);
 
    // Calculate the residence correction
    // frac will be 1 if the step is completely inside the lens, between 0 and 1
    // when entering or leaving the lens, and otherwise 0.
    // This accounts for the case when particles step over the element without landing in it.
    // This assumes that vzp != 0.
    amrex::ParticleReal const zl_bounded = std::min(std::max(zl, zs), ze);
    amrex::ParticleReal const zr_bounded = std::min(std::max(zr, zs), ze);
    const amrex::ParticleReal frac = (zr_bounded - zl_bounded)/(zr - zl);
 
    return frac;
}
 
#endif // WARPX_ACCELERATORLATTICE_LATTICEELEMENTS_HARDEDGED_K_H_