Interpolate_K.H

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#ifndef WARPX_INTERP_K_H_
#define WARPX_INTERP_K_H_

#include <AMReX_FArrayBox.H>

namespace Interpolate {

AMREX_GPU_DEVICE AMREX_FORCE_INLINE
void interp (int j, int k, int l,
             amrex::Array4<amrex::Real      > const& fine,
             amrex::Array4<amrex::Real const> const& crse,
             int r_ratio, IntVect const& type) noexcept
{
    using amrex::Real;
    Real const rr = 1.0_rt/static_cast<Real>(r_ratio);

    int const jg = amrex::coarsen(j,r_ratio);
    Real const wx = static_cast<Real>(type[0]) * static_cast<amrex::Real>(j-jg*r_ratio) * rr;
    Real const owx = 1.0_rt-wx;

    int const kg = amrex::coarsen(k,r_ratio);
    Real const wy = static_cast<Real>(type[1]) * static_cast<amrex::Real>(k-kg*r_ratio) * rr;
    Real const owy = 1.0_rt-wy;

#if (AMREX_SPACEDIM == 2)
    fine(j,k,l) = owx * owy * crse(jg  ,kg  ,0)
        +         owx *  wy * crse(jg  ,kg+1,0)
        +          wx * owy * crse(jg+1,kg  ,0)
        +          wx *  wy * crse(jg+1,kg+1,0);
#else
    int const lg = amrex::coarsen(l,r_ratio);
    Real const wz = static_cast<Real>(type[2]) * static_cast<amrex::Real>(l-lg*r_ratio) * rr;
    Real const owz = 1.0_rt-wz;
    fine(j,k,l) = owx * owy * owz * crse(jg  ,kg  ,lg  )
        +          wx * owy * owz * crse(jg+1,kg  ,lg  )
        +         owx *  wy * owz * crse(jg  ,kg+1,lg  )
        +          wx *  wy * owz * crse(jg+1,kg+1,lg  )
        +         owx * owy *  wz * crse(jg  ,kg  ,lg+1)
        +          wx * owy *  wz * crse(jg+1,kg  ,lg+1)
        +         owx *  wy *  wz * crse(jg  ,kg+1,lg+1)
        +          wx *  wy *  wz * crse(jg+1,kg+1,lg+1);
#endif
}

}

#endif