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/* Copyright 2020 Remi Lehe
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#include "FiniteDifferenceSolver.H"
#include "Utils/TextMsg.H"
#include "Utils/WarpXAlgorithmSelection.H"
#ifndef WARPX_DIM_RZ
# include "FiniteDifferenceAlgorithms/CartesianCKCAlgorithm.H"
# include "FiniteDifferenceAlgorithms/CartesianNodalAlgorithm.H"
# include "FiniteDifferenceAlgorithms/CartesianYeeAlgorithm.H"
#else
# include "FiniteDifferenceAlgorithms/CylindricalYeeAlgorithm.H"
#endif
#include <AMReX.H>
#include <AMReX_Array4.H>
#include <AMReX_Config.H>
#include <AMReX_Extension.H>
#include <AMReX_GpuContainers.H>
#include <AMReX_GpuControl.H>
#include <AMReX_GpuLaunch.H>
#include <AMReX_GpuQualifiers.H>
#include <AMReX_IndexType.H>
#include <AMReX_MFIter.H>
#include <AMReX_MultiFab.H>
#include <AMReX_REAL.H>
#include <AMReX_BaseFwd.H>
#include <array>
#include <memory>
using namespace amrex;
/**
* \brief Update the F field, over one timestep
*/
void FiniteDifferenceSolver::ComputeDivE (
const std::array<std::unique_ptr<amrex::MultiFab>,3>& Efield,
amrex::MultiFab& divEfield ) {
// Select algorithm (The choice of algorithm is a runtime option,
// but we compile code for each algorithm, using templates)
#ifdef WARPX_DIM_RZ
if (m_fdtd_algo == ElectromagneticSolverAlgo::Yee){
ComputeDivECylindrical <CylindricalYeeAlgorithm> ( Efield, divEfield );
#else
if (m_do_nodal) {
ComputeDivECartesian <CartesianNodalAlgorithm> ( Efield, divEfield );
} else if (m_fdtd_algo == ElectromagneticSolverAlgo::Yee) {
ComputeDivECartesian <CartesianYeeAlgorithm> ( Efield, divEfield );
} else if (m_fdtd_algo == ElectromagneticSolverAlgo::CKC) {
ComputeDivECartesian <CartesianCKCAlgorithm> ( Efield, divEfield );
#endif
} else {
amrex::Abort(Utils::TextMsg::Err("ComputeDivE: Unknown algorithm"));
}
}
#ifndef WARPX_DIM_RZ
template<typename T_Algo>
void FiniteDifferenceSolver::ComputeDivECartesian (
const std::array<std::unique_ptr<amrex::MultiFab>,3>& Efield,
amrex::MultiFab& divEfield ) {
// Loop through the grids, and over the tiles within each grid
#ifdef AMREX_USE_OMP
#pragma omp parallel if (amrex::Gpu::notInLaunchRegion())
#endif
for ( MFIter mfi(divEfield, TilingIfNotGPU()); mfi.isValid(); ++mfi ) {
// Extract field data for this grid/tile
Array4<Real> const& divE = divEfield.array(mfi);
Array4<Real> const& Ex = Efield[0]->array(mfi);
Array4<Real> const& Ey = Efield[1]->array(mfi);
Array4<Real> const& Ez = Efield[2]->array(mfi);
// Extract stencil coefficients
Real const * const AMREX_RESTRICT coefs_x = m_stencil_coefs_x.dataPtr();
int const n_coefs_x = m_stencil_coefs_x.size();
Real const * const AMREX_RESTRICT coefs_y = m_stencil_coefs_y.dataPtr();
int const n_coefs_y = m_stencil_coefs_y.size();
Real const * const AMREX_RESTRICT coefs_z = m_stencil_coefs_z.dataPtr();
int const n_coefs_z = m_stencil_coefs_z.size();
// Extract tileboxes for which to loop
Box const& tdive = mfi.tilebox(divEfield.ixType().toIntVect());
// Loop over the cells and update the fields
amrex::ParallelFor(tdive,
[=] AMREX_GPU_DEVICE (int i, int j, int k){
divE(i, j, k) =
T_Algo::DownwardDx(Ex, coefs_x, n_coefs_x, i, j, k)
+ T_Algo::DownwardDy(Ey, coefs_y, n_coefs_y, i, j, k)
+ T_Algo::DownwardDz(Ez, coefs_z, n_coefs_z, i, j, k);
}
);
}
}
#else // corresponds to ifndef WARPX_DIM_RZ
template<typename T_Algo>
void FiniteDifferenceSolver::ComputeDivECylindrical (
const std::array<std::unique_ptr<amrex::MultiFab>,3>& Efield,
amrex::MultiFab& divEfield ) {
// Loop through the grids, and over the tiles within each grid
#ifdef AMREX_USE_OMP
#pragma omp parallel if (amrex::Gpu::notInLaunchRegion())
#endif
for ( MFIter mfi(divEfield, TilingIfNotGPU()); mfi.isValid(); ++mfi ) {
// Extract field data for this grid/tile
Array4<Real> divE = divEfield.array(mfi);
Array4<Real> const& Er = Efield[0]->array(mfi);
Array4<Real> const& Et = Efield[1]->array(mfi);
Array4<Real> const& Ez = Efield[2]->array(mfi);
// Extract stencil coefficients
Real const * const AMREX_RESTRICT coefs_r = m_stencil_coefs_r.dataPtr();
int const n_coefs_r = m_stencil_coefs_r.size();
Real const * const AMREX_RESTRICT coefs_z = m_stencil_coefs_z.dataPtr();
int const n_coefs_z = m_stencil_coefs_z.size();
// Extract cylindrical specific parameters
Real const dr = m_dr;
int const nmodes = m_nmodes;
Real const rmin = m_rmin;
// Extract tileboxes for which to loop
Box const& tdive = mfi.tilebox(divEfield.ixType().toIntVect());
// Loop over the cells and update the fields
amrex::ParallelFor(tdive,
[=] AMREX_GPU_DEVICE (int i, int j, int /*k*/){
Real const r = rmin + i*dr; // r on a nodal grid (F is nodal in r)
if (r != 0) { // Off-axis, regular equations
divE(i, j, 0, 0) =
T_Algo::DownwardDrr_over_r(Er, r, dr, coefs_r, n_coefs_r, i, j, 0, 0)
+ T_Algo::DownwardDz(Ez, coefs_z, n_coefs_z, i, j, 0, 0);
for (int m=1 ; m<nmodes ; m++) { // Higher-order modes
divE(i, j, 0, 2*m-1) =
T_Algo::DownwardDrr_over_r(Er, r, dr, coefs_r, n_coefs_r, i, j, 0, 2*m-1)
+ m * Et( i, j, 0, 2*m )/r
+ T_Algo::DownwardDz(Ez, coefs_z, n_coefs_z, i, j, 0, 2*m-1); // Real part
divE(i, j, 0, 2*m ) =
T_Algo::DownwardDrr_over_r(Er, r, dr, coefs_r, n_coefs_r, i, j, 0, 2*m)
- m * Et( i, j, 0, 2*m-1 )/r
+ T_Algo::DownwardDz(Ez, coefs_z, n_coefs_z, i, j, 0, 2*m ); // Imaginary part
}
} else { // r==0: on-axis corrections
// For m==0, Er is linear in r, for small r
// Therefore, the formula below regularizes the singularity
divE(i, j, 0, 0) =
4._rt*Er(i, j, 0, 0)/dr // regularization
+ T_Algo::DownwardDz(Ez, coefs_z, n_coefs_z, i, j, 0, 0);
// Ensure that divE remains 0 for higher-order modes
for (int m=1; m<nmodes; m++) {
divE(i, j, 0, 2*m-1) = 0._rt;
divE(i, j, 0, 2*m ) = 0._rt;
}
}
}
); // end of loop over cells
} // end of loop over grid/tiles
}
#endif // corresponds to ifndef WARPX_DIM_RZ
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