Expression.H

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//
// Initialize a field using a mathematical expression.
// Expressions are imported as strings and are compiled real-time using the
// `AMReX Parser <https://amrex-codes.github.io/amrex/docs_html/Basics.html#parser>`_.
//
// Works for single or multiple-component fields.
// Use the :code:`regionN` (N=0,1,2, etc. up to number of components) to pass expression.
// For example:
//
// .. code-block:: bash
// 
//    ic.region0 = "sin(x*y*z)"
//    ic.region1 = "3.0*(x > 0.5 and y > 0.5)"
//
// for a two-component field. It is up to you to make sure your expressions are parsed
// correctly; otherwise you will get undefined behavior.
//
// :bdg-primary-line:`Constants`
// You can add constants to your expressions using the :code:`constant` directive.
// For instance, in the following code
// 
// .. code-block:: bash
//
//    psi.ic.type=expression
//    psi.ic.expression.constant.eps = 0.05
//    psi.ic.expression.constant.R   = 0.25
//    psi.ic.expression.region0 = "0.5 + 0.5*tanh((x^2 + y^2 - R)/eps)"
//    
// the constants :code:`eps` and :code:`R` are defined by the user and then used
// in the subsequent expression.
// The variables can have any name made up of characters that is not reserved.
// However, if multiple ICs are used, they must be defined each time for each IC.
//
 
#ifndef IC_EXPRESSION_H_
#define IC_EXPRESSION_H_
#include "IC/IC.H"
#include "Util/Util.H"
#include "IO/ParmParse.H"
#include "AMReX_Parser.H"
 
namespace IC
{
class Expression : public IC<Set::Scalar>, public IC<Set::Vector>
{
private:
    enum CoordSys { Cartesian, Polar, Spherical };
    std::vector<amrex::Parser> parser;
    std::vector<amrex::ParserExecutor<4>> f;
    Expression::CoordSys coord = Expression::CoordSys::Cartesian;
public:
    static constexpr const char* name = "expression";
    Expression(amrex::Vector<amrex::Geometry>& _geom) : 
        IC<Set::Scalar>(_geom), IC<Set::Vector>(_geom) {}
    Expression(amrex::Vector<amrex::Geometry>& _geom, IO::ParmParse& pp, std::string name) : 
        IC<Set::Scalar>(_geom), IC<Set::Vector>(_geom)
    {
        pp_queryclass(name, *this);
    }
    virtual void Add(const int& lev, Set::Field<Set::Scalar>& a_field, Set::Scalar a_time = 0.0) override
    {
        Util::Assert(INFO, TEST(a_field[lev]->nComp() == (int)f.size()));
        for (amrex::MFIter mfi(*a_field[lev], amrex::TilingIfNotGPU()); mfi.isValid(); ++mfi)
        {
            amrex::Box bx;// = mfi.tilebox();
            //bx.grow(a_field[lev]->nGrow());
            amrex::IndexType type = a_field[lev]->ixType();
            if (type == amrex::IndexType::TheCellType())      bx = mfi.growntilebox();
            else if (type == amrex::IndexType::TheNodeType()) bx = mfi.grownnodaltilebox();
            else Util::Abort(INFO, "Unkonwn index type");
 
            amrex::Array4<Set::Scalar> const& field = a_field[lev]->array(mfi);
            for (unsigned int n = 0; n < f.size(); n++)
            {
                amrex::ParallelFor(bx, [=] AMREX_GPU_DEVICE(int i, int j, int k)
                {
                    Set::Vector x = Set::Position(i, j, k, IC<Set::Scalar>::geom[lev], type);
                    if (coord == Expression::CoordSys::Cartesian)
                    {
#if AMREX_SPACEDIM == 1
                        field(i, j, k, n) = f[n](x(0), 0.0, 0.0, a_time);
#elif AMREX_SPACEDIM == 2
                        field(i, j, k, n) = f[n](x(0), x(1), 0.0, a_time);
#elif AMREX_SPACEDIM == 3
                        field(i, j, k, n) = f[n](x(0), x(1), x(2), a_time);
#endif
                    }
#if AMREX_SPACEDIM>1
                    else if (coord == Expression::CoordSys::Polar)
                    {
                        field(i, j, k, n) = f[n](sqrt(x(0)* x(0) + x(1) * x(1)), std::atan2(x(1), x(0)), x(2), a_time);
                    }
#endif
                });
            }
        }
        a_field[lev]->FillBoundary();
    };
 
    virtual void Add(const int& lev, Set::Field<Set::Vector>& a_field, Set::Scalar a_time = 0.0) override
    {
        Util::Assert(INFO, TEST(a_field[lev]->nComp() == 1));
        Util::Assert(INFO, TEST(f.size() >= AMREX_SPACEDIM));
        for (amrex::MFIter mfi(*a_field[lev], amrex::TilingIfNotGPU()); mfi.isValid(); ++mfi)
        {
            amrex::Box bx;
            amrex::IndexType type = a_field[lev]->ixType();
            if (type == amrex::IndexType::TheCellType())      bx = mfi.growntilebox();
            else if (type == amrex::IndexType::TheNodeType()) bx = mfi.grownnodaltilebox();
            else Util::Abort(INFO, "Unkonwn index type");
 
            Set::Patch<Set::Vector> field = a_field.Patch(lev,mfi);
            for (unsigned int n = 0; n < AMREX_SPACEDIM; n++)
            {
                amrex::ParallelFor(bx, [=] AMREX_GPU_DEVICE(int i, int j, int k)
                {
                    Set::Vector x = Set::Position(i, j, k, IC<Set::Vector>::geom[lev], type);
                    if (coord == Expression::CoordSys::Cartesian)
                    {
#if AMREX_SPACEDIM == 1
                        field(i, j, k)(n) = f[n](x(0), 0.0, 0.0, a_time);
#elif AMREX_SPACEDIM == 2
                        field(i, j, k)(n) = f[n](x(0), x(1), 0.0, a_time);
#elif AMREX_SPACEDIM == 3
                        field(i, j, k)(n) = f[n](x(0), x(1), x(2), a_time);
#endif
                    }
#if AMREX_SPACEDIM>1
                    else if (coord == Expression::CoordSys::Polar)
                    {
                        field(i, j, k)(n) = f[n](sqrt(x(0)* x(0) + x(1) * x(1)), std::atan2(x(1), x(0)), x(2), a_time);
                    }
#endif
                });
            }
        }
        a_field[lev]->FillBoundary();
    };
 
    static void Parse(Expression& value, IO::ParmParse& pp)
    {
 
        std::string coordstr = "";
        // coordinate system to use
        pp_query_validate("coord", coordstr, {"cartesian","polar"}); 
        if (coordstr == "cartesian") value.coord = Expression::CoordSys::Cartesian;
        else if (coordstr == "polar") value.coord = Expression::CoordSys::Polar;
        else Util::Abort(INFO, "unsupported coordinates ", coordstr);
 
        std::vector<std::string> expression_strs;
        // Mathematical expression in terms of x,y,z,t (if coord=cartesian)
        // or r,theta,z,t (if coord=polar) and any defined constants.
        pp.query_enumerate("region", expression_strs);
 
        for (unsigned int i = 0; i < expression_strs.size(); i++)
        {
            value.parser.push_back(amrex::Parser(expression_strs[i]));
 
            //
            // Read in user-defined constants and add them to the parser
            //
            std::string prefix = pp.getPrefix();
            std::set<std::string> entries = pp.getEntries(prefix + ".constant");//"constant");
            std::set<std::string>::iterator entry;
            for (entry = entries.begin(); entry != entries.end(); entry++)
            {
                IO::ParmParse pp;
                std::string fullname = *entry;
                Set::Scalar val  = NAN;
                pp_query(fullname.data(),val);
                std::string name = Util::String::Split(fullname,'.').back();
                value.parser.back().setConstant(name,val);
            }
 
            if (value.coord == Expression::CoordSys::Cartesian)
            {
                value.parser.back().registerVariables({ "x","y","z","t" });
                value.f.push_back(value.parser.back().compile<4>());
            }
            else if (value.coord == Expression::CoordSys::Polar)
            {
                value.parser.back().registerVariables({ "r","theta","z","t" });
                value.f.push_back(value.parser.back().compile<4>());
            }
        }
 
    };
};
}
 
#endif