Q4.H

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#ifndef FINITEELEMENT_Q4_
#define FINITEELEMENT_Q4_
 
#include "Set/Set.H"
 
namespace FiniteElement
{
class Q4
{
public:
    Q4() {};
    Q4(amrex::Real _dx, amrex::Real _dy): dx(_dx), dy(_dy) {};
    void Define(Set::Scalar a_dx, Set::Scalar a_dy)
    {
        dx = a_dx; dy = a_dy;
    }
 
    AMREX_FORCE_INLINE
        Set::Scalar Phi(int m, const Set::Vector x) const
    {
        if (m == 0) return (dx - x(0)) * (dy - x(1)) / dx / dy;
        if (m == 1) return (x(0) - 0.0) * (dy - x(1)) / dx / dy;
        if (m == 2) return (dx - x(0)) * (x(1) - 0.0) / dx / dy;
        if (m == 3) return (x(0) - 0.0) * (x(1) - 0.0) / dx / dy;
    }
 
    AMREX_FORCE_INLINE
        Set::Vector DPhi(int m, const Set::Vector x) const
    {
        if (m == 0) return { AMREX_D_DECL(-(dy - x(1)) / dx / dy,-(dx - x(0)) / dx / dy,0) };
        if (m == 1) return { AMREX_D_DECL((dy - x(1)) / dx / dy,-x(0) / dx / dy,0) };
        if (m == 2) return { AMREX_D_DECL(-x(1) / dx / dy,(dx - x(0)) / dx / dy,0) };
        if (m == 3) return { AMREX_D_DECL(x(1) / dx / dy, x(0) / dx / dy,0) };
    }
 
    Set::Vector Qpt(const int m) const { return qpts[m]; }
    Set::Scalar Qwt(const int m) const { return qwts[m]; }
 
private:
    Set::Scalar dx, dy;
    const std::array<Set::Vector, 4> qpts =
    {
        Set::Vector(0.5 - 0.5 / sqrt(3.0),0.5 - 0.5 / sqrt(3.0)),
        Set::Vector(0.5 - 0.5 / sqrt(3.0),0.5 + 0.5 / sqrt(3.0)),
        Set::Vector(0.5 + 0.5 / sqrt(3.0),0.5 - 0.5 / sqrt(3.0)),
        Set::Vector(0.5 + 0.5 / sqrt(3.0),0.5 + 0.5 / sqrt(3.0))
    };
    const std::array<Set::Scalar, 4> qwts = { 1.0, 1.0, 1.0, 1.0 };
 
};
}
#endif