sample.H

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/* Copyright 2022 Edoardo Zoni, Remi Lehe, David Grote, Axel Huebl
 *
 * This file is part of ABLASTR.
 *
 * License: BSD-3-Clause-LBNL
 */
#ifndef ABLASTR_COARSEN_SAMPLE_H_
#define ABLASTR_COARSEN_SAMPLE_H_
 
 
#include <AMReX_Array.H>
#include <AMReX_Array4.H>
#include <AMReX_Extension.H>
#include <AMReX_GpuQualifiers.H>
#include <AMReX_IntVect.H>
#include <AMReX_Math.H>
#include <AMReX_REAL.H>
 
#include <AMReX_BaseFwd.H>
 
#include <cstdlib>
 

namespace ablastr::coarsen::sample
{
    AMREX_GPU_DEVICE
    AMREX_FORCE_INLINE
    amrex::Real Interp (
        amrex::Array4<amrex::Real const> const& arr_src,
        amrex::GpuArray<int,3> const& sf,
        amrex::GpuArray<int,3> const& sc,
        amrex::GpuArray<int,3> const& cr,
        const int i,
        const int j,
        const int k,
        const int comp
    )
    {
        using namespace amrex::literals;
 
        // Indices of destination array (coarse)
        const int ic[3] = { i, j, k };
 
        // Number of points and starting indices of source array (fine)
        int np[3], idx_min[3];
 
        // Compute number of points
        for ( int l = 0; l < 3; ++l ) {
            if ( cr[l] == 1 ) { np[l] = 1+amrex::Math::abs(sf[l]-sc[l]); // no coarsening
            } else {            np[l] = 2-sf[l]; }
        }
 
        // Compute starting indices of source array (fine)
        for ( int l = 0; l < 3; ++l ) {
            if ( cr[l] == 1 ) { idx_min[l] = ic[l]-sc[l]*(1-sf[l]); // no coarsening
            } else {            idx_min[l] = ic[l]*cr[l]+static_cast<int>(cr[l]/2)*(1-sc[l])-(1-sf[l]); }
        }
 
        // Auxiliary integer variables
        const int numx = np[0];
        const int numy = np[1];
        const int numz = np[2];
        const int imin = idx_min[0];
        const int jmin = idx_min[1];
        const int kmin = idx_min[2];
        amrex::Real const wx = 1.0_rt / static_cast<amrex::Real>(numx);
        amrex::Real const wy = 1.0_rt / static_cast<amrex::Real>(numy);
        amrex::Real const wz = 1.0_rt / static_cast<amrex::Real>(numz);
 
        // Interpolate over points computed above
        amrex::Real c = 0.0_rt;
        for         (int kref = 0; kref < numz; ++kref) {
            for     (int jref = 0; jref < numy; ++jref) {
                for (int iref = 0; iref < numx; ++iref) {
                    const int ii = imin+iref;
                    const int jj = jmin+jref;
                    const int kk = kmin+kref;
                    c += wx*wy*wz*arr_src(ii,jj,kk,comp);
                }
            }
        }
        return c;
    }

    void Loop ( amrex::MultiFab& mf_dst,
                const amrex::MultiFab& mf_src,
                int dcomp,
                int scomp,
                int ncomp,
                amrex::IntVect ngrow,
                amrex::IntVect crse_ratio=amrex::IntVect(1) );

    void Coarsen ( amrex::MultiFab& mf_dst,
                   const amrex::MultiFab& mf_src,
                   int dcomp,
                   int scomp,
                   int ncomp,
                   int ngrow,
                   amrex::IntVect crse_ratio=amrex::IntVect(1) );
    void Coarsen ( amrex::MultiFab& mf_dst,
                   const amrex::MultiFab& mf_src,
                   int dcomp,
                   int scomp,
                   int ncomp,
                   amrex::IntVect ngrowvect,
                   amrex::IntVect crse_ratio=amrex::IntVect(1) );
 
} // namespace ablastr::coarsen::sample
 
#endif // ABLASTR_COARSEN_SAMPLE_H_