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/* Copyright 2019 Axel Huebl, Maxence Thevenet, Weiqun Zhang
* Michael Rowan
*
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
#ifndef INJECTOR_DENSITY_H_
#define INJECTOR_DENSITY_H_
#include "Utils/WarpXConst.H"
#include <AMReX.H>
#include <AMReX_Array.H>
#include <AMReX_GpuQualifiers.H>
#include <AMReX_Math.H>
#include <AMReX_Parser.H>
#include <AMReX_REAL.H>
#include <cmath>
#include <string>
// struct whose getDensity returns constant density.
struct InjectorDensityConstant
{
InjectorDensityConstant (amrex::Real a_rho) noexcept : m_rho(a_rho) {}
AMREX_GPU_HOST_DEVICE
amrex::Real
getDensity (amrex::Real, amrex::Real, amrex::Real) const noexcept
{
return m_rho;
}
private:
amrex::Real m_rho;
};
// struct whose getDensity returns local density computed from parser.
struct InjectorDensityParser
{
InjectorDensityParser (amrex::ParserExecutor<3> const& a_parser) noexcept
: m_parser(a_parser) {}
AMREX_GPU_HOST_DEVICE
amrex::Real
getDensity (amrex::Real x, amrex::Real y, amrex::Real z) const noexcept
{
return m_parser(x,y,z);
}
amrex::ParserExecutor<3> m_parser;
};
// struct whose getDensity returns local density computed from predefined profile.
struct InjectorDensityPredefined
{
InjectorDensityPredefined (std::string const& a_species_name) noexcept;
void clear ();
AMREX_GPU_HOST_DEVICE
amrex::Real
getDensity (amrex::Real x, amrex::Real y, amrex::Real z) const noexcept
{
// Choices for profile are:
// - parabolic_channel
switch (profile)
{
case Profile::parabolic_channel:
{
// These are cast as double to ensure sufficient precision in the
// initialized profile density profile; without these, single and
// double precision versions of the executable can show disagreement
// From testing, it seems that (for at least some setups), it is only
// necessary to case n0 as double to get good agreement between single
// and double precision, but just in case, all are cast as double.
const double z_start = p[0];
const double ramp_up = p[1];
const double plateau = p[2];
const double ramp_down = p[3];
const double rc = p[4];
const double n0 = p[5];
const double kp = PhysConst::q_e/PhysConst::c
*std::sqrt( n0/(PhysConst::m_e*PhysConst::ep0) );
double n;
// Longitudinal profile, normalized to 1
if ((z-z_start)>=0 and
(z-z_start)<ramp_up ) {
n = 0.5*(1.-std::cos(MathConst::pi*(z-z_start)/ramp_up));
} else if ((z-z_start)>=ramp_up and
(z-z_start)< ramp_up+plateau ) {
n = 1.;
} else if ((z-z_start)>=ramp_up+plateau and
(z-z_start)< ramp_up+plateau+ramp_down) {
n = 0.5*(1.+std::cos(MathConst::pi*((z-z_start)-ramp_up-plateau)/ramp_down));
} else {
n = 0.;
}
// Multiply by transverse profile, and physical density
n *= n0*(1.+4.*(x*x+y*y)/(kp*kp*rc*rc*rc*rc));
return static_cast<amrex::Real>(n);
}
default:
amrex::Abort("InjectorDensityPredefined: how did we get here?");
return amrex::Real(0.0);
}
}
private:
enum struct Profile { null, parabolic_channel };
Profile profile;
amrex::GpuArray<amrex::Real,6> p;
};
// Base struct for density injector.
// InjectorDensity contains a union (called Object) that holds any one
// instance of:
// - InjectorDensityConstant : to generate constant density;
// - InjectorDensityParser : to generate density from parser;
// - InjectorDensityPredefined: to generate density from predefined profile;
// The choice is made at runtime, depending in the constructor called.
// This mimics virtual functions.
struct InjectorDensity
{
// This constructor stores a InjectorDensityConstant in union object.
InjectorDensity (InjectorDensityConstant* t, amrex::Real a_rho)
: type(Type::constant),
object(t,a_rho)
{ }
// This constructor stores a InjectorDensityParser in union object.
InjectorDensity (InjectorDensityParser* t, amrex::ParserExecutor<3> const& a_parser)
: type(Type::parser),
object(t,a_parser)
{ }
// This constructor stores a InjectorDensityPredefined in union object.
InjectorDensity (InjectorDensityPredefined* t, std::string const& a_species_name)
: type(Type::predefined),
object(t,a_species_name)
{ }
// Explicitly prevent the compiler from generating copy constructors
// and copy assignment operators.
InjectorDensity (InjectorDensity const&) = delete;
InjectorDensity (InjectorDensity&&) = delete;
void operator= (InjectorDensity const&) = delete;
void operator= (InjectorDensity &&) = delete;
void clear ();
// call getDensity from the object stored in the union
// (the union is called Object, and the instance is called object).
AMREX_GPU_HOST_DEVICE
amrex::Real
getDensity (amrex::Real x, amrex::Real y, amrex::Real z) const noexcept
{
switch (type)
{
case Type::parser:
{
return object.parser.getDensity(x,y,z);
}
case Type::constant:
{
return object.constant.getDensity(x,y,z);
}
case Type::predefined:
{
return object.predefined.getDensity(x,y,z);
}
default:
{
amrex::Abort("InjectorDensity: unknown type");
return 0.0;
}
}
}
private:
enum struct Type { constant, predefined, parser };
Type type;
// An instance of union Object constructs and stores any one of
// the objects declared (constant or parser or predefined).
union Object {
Object (InjectorDensityConstant*, amrex::Real a_rho) noexcept
: constant(a_rho) {}
Object (InjectorDensityParser*, amrex::ParserExecutor<3> const& a_parser) noexcept
: parser(a_parser) {}
Object (InjectorDensityPredefined*, std::string const& a_species_name) noexcept
: predefined(a_species_name) {}
InjectorDensityConstant constant;
InjectorDensityParser parser;
InjectorDensityPredefined predefined;
};
Object object;
};
// In order for InjectorDensity to be trivially copyable, its destructor
// must be trivial. So we have to rely on a custom deleter for unique_ptr.
struct InjectorDensityDeleter {
void operator () (InjectorDensity* p) const {
if (p) {
p->clear();
delete p;
}
}
};
#endif
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