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/* Copyright 2021 Axel Huebl
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#ifndef PARTICLEIO_H_
#define PARTICLEIO_H_
#include "Particles/WarpXParticleContainer.H"
#include <AMReX_AmrParticles.H>
#include <AMReX_Gpu.H>
#include <AMReX_REAL.H>
enum struct ConvertDirection{WarpX_to_SI, SI_to_WarpX};
/** Convert particle momentum to/from SI
*
* Particle momentum is defined as gamma*velocity, which is neither
* SI mass*gamma*velocity nor normalized gamma*velocity/c.
* This converts momentum to SI units (or vice-versa) to write SI data
* to file.
* Photons are a special case, since particle momentum is defined as
* (photon_energy/(m_e * c) ) * u, where u is the photon direction (a
* unit vector).
*
* @tparam T_ParticleContainer a WarpX particle container or AmrParticleContainer
* @param convert_direction convert to or from SI
* @param pc the particle container to manipulate
* @param mass the particle rest mass to use for conversion
*/
template< typename T_ParticleContainer >
void
particlesConvertUnits (ConvertDirection convert_direction, T_ParticleContainer* pc, amrex::ParticleReal const mass )
{
using namespace amrex;
// Compute conversion factor
auto factor = 1_rt;
if (convert_direction == ConvertDirection::WarpX_to_SI){
factor = mass;
} else if (convert_direction == ConvertDirection::SI_to_WarpX){
factor = 1._rt/mass;
}
const int nLevels = pc->finestLevel();
for (int lev=0; lev<=nLevels; lev++){
#ifdef AMREX_USE_OMP
#pragma omp parallel if (Gpu::notInLaunchRegion())
#endif
for (ParIter pti(*pc, lev); pti.isValid(); ++pti)
{
// - momenta are stored as a struct of array, in `attribs`
// The GetStructOfArrays is called directly since the convenience routine GetAttribs
// is only available in WarpXParIter. ParIter is used here since the pc passed in
// will sometimes be a PinnedMemoryParticleContainer (not derived from a WarpXParticleContainer).
auto& attribs = pti.GetStructOfArrays().GetRealData();
ParticleReal* AMREX_RESTRICT ux = attribs[PIdx::ux].dataPtr();
ParticleReal* AMREX_RESTRICT uy = attribs[PIdx::uy].dataPtr();
ParticleReal* AMREX_RESTRICT uz = attribs[PIdx::uz].dataPtr();
// Loop over the particles and convert momentum
const long np = pti.numParticles();
ParallelFor( np,
[=] AMREX_GPU_DEVICE (long i) {
ux[i] *= factor;
uy[i] *= factor;
uz[i] *= factor;
}
);
}
}
}
#endif /* PARTICLEIO_H_ */
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