AMReX_EB2_Level.H

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#ifndef AMREX_EB2_LEVEL_H_
#define AMREX_EB2_LEVEL_H_
#include <AMReX_Config.H>
 
#include <AMReX_ParmParse.H>
#include <AMReX_Geometry.H>
#include <AMReX_MultiFab.H>
#include <AMReX_iMultiFab.H>
#include <AMReX_LayoutData.H>
#include <AMReX_VisMF.H>
#include <AMReX_Array.H>
#include <AMReX_EBCellFlag.H>
#include <AMReX_MultiCutFab.H>
#if (AMREX_SPACEDIM == 3)
#  include <AMReX_MarchingCubes.H>
#endif
#include <AMReX_EB2_MultiGFab.H>
#include <AMReX_EB2_C.H>
#include <AMReX_EB2_IF_AllRegular.H>
 
#ifdef AMREX_USE_OMP
#include <omp.h>
#endif
 
#include <cmath>
#include <limits>
#include <map>
#include <type_traits>
#include <unordered_map>
 
namespace amrex
{
    class STLtools;
}
 
namespace amrex::EB2 {
 
class IndexSpace;
template <typename G> class GShopLevel;
template <typename G> class IndexSpaceImp;
 
class Level
{
public:
 
    bool isAllRegular () const noexcept { return m_allregular; }
    bool isOK () const noexcept { return m_ok; }
    void fillEBCellFlag (FabArray<EBCellFlagFab>& cellflag, const Geometry& geom) const;
    void fillVolFrac (MultiFab& vfrac, const Geometry& geom) const;
    void fillCentroid (MultiCutFab& centroid, const Geometry& geom) const;
    void fillCentroid (   MultiFab& centroid, const Geometry& geom) const;
    void fillBndryArea (MultiCutFab& bndryarea, const Geometry& geom) const;
    void fillBndryArea (   MultiFab& bndryarea, const Geometry& geom) const;
    void fillBndryCent (MultiCutFab& bndrycent, const Geometry& geom) const;
    void fillBndryCent (   MultiFab& bndrycent, const Geometry& geom) const;
    void fillBndryNorm (MultiCutFab& bndrynorm, const Geometry& geom) const;
    void fillBndryNorm (   MultiFab& bndrynorm, const Geometry& geom) const;
    void fillAreaFrac (Array<MultiCutFab*,AMREX_SPACEDIM> const& areafrac, const Geometry& geom) const;
    void fillAreaFrac (Array<   MultiFab*,AMREX_SPACEDIM> const& areafrac, const Geometry& geom) const;
    void fillFaceCent (Array<MultiCutFab*,AMREX_SPACEDIM> const& facecent, const Geometry& geom) const;
    void fillFaceCent (Array<   MultiFab*,AMREX_SPACEDIM> const& facecent, const Geometry& geom) const;
    void fillEdgeCent (Array<MultiCutFab*,AMREX_SPACEDIM> const& edgecent, const Geometry& geom) const;
    void fillEdgeCent (Array<   MultiFab*,AMREX_SPACEDIM> const& edgecent, const Geometry& geom) const;
    void fillLevelSet (MultiFab& levelset, const Geometry& geom) const;
 
    const BoxArray& boxArray () const noexcept { return m_grids; }
    const DistributionMapping& DistributionMap () const noexcept { return m_dmap; }
 
    Level (IndexSpace const* is, const Geometry& geom) : m_geom(geom), m_parent(is) {}
    void prepareForCoarsening (const Level& rhs, int max_grid_size, IntVect const& ngrow);
 
    const Geometry& Geom () const noexcept { return m_geom; }
    IndexSpace const* getEBIndexSpace () const noexcept { return m_parent; }
 
    IntVect const& nGrowVect () const noexcept { return m_ngrow; }
 
    void write_to_chkpt_file (const std::string& fname, bool extend_domain_face, int max_grid_size) const;
 
    bool hasEBInfo () const noexcept { return m_has_eb_info; }
    void fillCutCellMask (iMultiFab& cutcellmask, const Geometry& geom) const;
 
    void setShift (int direction, int ncells);
 
    struct FCData {
        FabArray<EBCellFlagFab> m_cellflag_fc;
        MultiFab m_volfrac_fc;
        MultiFab m_centroid_fc;
        MultiFab m_bndryarea_fc;
        MultiFab m_bndrycent_fc;
        MultiFab m_bndrynorm_fc;
        Array<MultiFab,AMREX_SPACEDIM> m_areafrac_fc;
        Array<MultiFab,AMREX_SPACEDIM> m_facecent_fc;
        Array<MultiFab,AMREX_SPACEDIM> m_edgecent_fc;
        // Covered region of the refined level, coarsened onto this level. The refined level
        // is transient, so this has to be captured while it exists. It is not the same as
        // Level::m_covered_grids: the refined level resolves the body more finely, so once
        // coarsened its covered region is the larger of the two, and it is the one that
        // matches where the face-centered data was computed.
        //
        // The fill*FC functions apply it before their ParallelCopy, and deliberately do not
        // shrink it first. A face-centered cell straddles two cell-centered cells, so the
        // ones on the covered/cut interface may themselves be cut; clearing them here and
        // letting the copy write over them is correct, because the copy writes exactly where
        // the face-centered data is valid - the nodal span of the cut boxes, which reaches
        // the interface and no further. Ordering does the shrinking, so no box has to be
        // trimmed and two adjacent covered boxes need no special treatment.
        BoxArray m_covered_grids_fc;
        bool m_built = false;
    };
 
    [[nodiscard]] static IntVect fcEdgeType (int idim, int face_dir) noexcept {
        IntVect edge_type{1};
        if (idim != face_dir) { edge_type[idim] = 0; }
        return edge_type;
    }
 
    [[nodiscard]] bool hasFCData (int face_dir) const noexcept {
        return face_dir >= 0 && face_dir < AMREX_SPACEDIM &&
               m_fc_data[face_dir] && m_fc_data[face_dir]->m_built;
    }
 
    [[nodiscard]] const FCData& getFCData (int face_dir) const {
        AMREX_ASSERT(hasFCData(face_dir));
        return *m_fc_data[face_dir];
    }
 
    void fillVolFracFC (MultiFab& vfrac, int face_dir, const Geometry& geom) const;
    void fillAreaFracFC (Array<   MultiFab*,AMREX_SPACEDIM> const& areafrac, int face_dir, const Geometry& geom) const;
    void fillAreaFracFC (Array<MultiCutFab*,AMREX_SPACEDIM> const& areafrac, int face_dir, const Geometry& geom) const;
    void fillCentroidFC (MultiFab& centroid, int face_dir, const Geometry& geom) const;
    void fillCentroidFC (MultiCutFab& centroid, int face_dir, const Geometry& geom) const;
    void fillBndryAreaFC (MultiFab& bndryarea, int face_dir, const Geometry& geom) const;
    void fillBndryAreaFC (MultiCutFab& bndryarea, int face_dir, const Geometry& geom) const;
    void fillBndryCentFC (MultiFab& bndrycent, int face_dir, const Geometry& geom) const;
    void fillBndryCentFC (MultiCutFab& bndrycent, int face_dir, const Geometry& geom) const;
    void fillBndryNormFC (MultiFab& bndrynorm, int face_dir, const Geometry& geom) const;
    void fillBndryNormFC (MultiCutFab& bndrynorm, int face_dir, const Geometry& geom) const;
    void fillEBCellFlagFC (FabArray<EBCellFlagFab>& cellflag, int face_dir, const Geometry& geom) const;
    void fillFaceCentFC (Array<   MultiFab*,AMREX_SPACEDIM> const& facecent, int face_dir, const Geometry& geom) const;
    void fillFaceCentFC (Array<MultiCutFab*,AMREX_SPACEDIM> const& facecent, int face_dir, const Geometry& geom) const;
    void fillEdgeCentFC (Array<   MultiFab*,AMREX_SPACEDIM> const& edgecent, int face_dir, const Geometry& geom) const;
    void fillEdgeCentFC (Array<MultiCutFab*,AMREX_SPACEDIM> const& edgecent, int face_dir, const Geometry& geom) const;
 
// public: // for cuda
    int coarsenFromFine (Level& fineLevel, bool fill_boundary);
    void buildCellFlag ();
    void buildCellFlagFC (int face_dir);
    void buildCutCellMask (Level const& fine_level);
 
protected:
 
    Geometry m_geom;
    IntVect  m_ngrow;
    BoxArray m_grids;
    BoxArray m_covered_grids;
    DistributionMapping m_dmap;
    MultiFab m_sdf;
#if (AMREX_SPACEDIM == 3)
    std::map<int,std::unique_ptr<MC::MCFab>> m_marching_cubes;
#endif
    MultiGFab m_mgf;
    MultiFab m_levelset;
    FabArray<EBCellFlagFab> m_cellflag;
    MultiFab m_volfrac;
    MultiFab m_centroid;
    MultiFab m_bndryarea;
    MultiFab m_bndrycent;
    MultiFab m_bndrynorm;
    Array<MultiFab,AMREX_SPACEDIM> m_areafrac;
    Array<MultiFab,AMREX_SPACEDIM> m_facecent;
    Array<MultiFab,AMREX_SPACEDIM> m_edgecent;
    iMultiFab m_cutcellmask;
    bool m_allregular = false;
    bool m_ok = false;
    bool m_has_eb_info = true;
    IntVect m_shift{0};
    IndexSpace const* m_parent;
 
    Array<std::unique_ptr<FCData>, AMREX_SPACEDIM> m_fc_data;
 
private:
    template <typename G> friend class GShopLevel;
    // So that it can update m_parent when a level changes owner.
    template <typename G> friend class IndexSpaceImp;
 
    // Need this function to work around a gcc bug.
    void setRegularLevel () {
        m_allregular = true;
        m_ok = true;
        m_has_eb_info = false;
    }
};
 
template <typename G>
class GShopLevel
    : public Level
{
public:
    GShopLevel (IndexSpace const* is, G const& gshop, const Geometry& geom, int max_grid_size,
                int ngrow, bool extend_domain_face, int num_crse_opt);
    GShopLevel (IndexSpace const* is, int ilev, int max_grid_size, int ngrow,
                const Geometry& geom, GShopLevel<G>& fineLevel);
    GShopLevel (IndexSpace const* is, const Geometry& geom);
    void define_fine (G const& gshop, const Geometry& geom,
                      int max_grid_size, int ngrow, bool extend_domain_face, int num_crse_opt);
 
#if (AMREX_SPACEDIM == 3)
    template <typename GS = G>
    requires (std::same_as<GS,STLtools>)
    void define_fine_mvmc (GS const& gshop, const Geometry& geom,
                           int max_grid_size, int ngrow, bool extend_domain_face, int num_crse_opt);
#endif
 
    static GShopLevel<G>
    makeAllRegular(IndexSpace const* is, const Geometry& geom)
    {
        GShopLevel<G> r(is, geom);
        r.setRegularLevel();
        return r;
    }
 
    void buildFCData (G const& gshop, int face_dir, int max_grid_size);
 
private:
 
    Box m_bounding_box;
 
    void prepare_grids (G const& gshop, Geometry const& geom, int max_grid_size, int ngrow,
                        bool extend_domain_face, int num_crse_opt);
 
};
 
template <typename G>
GShopLevel<G>::GShopLevel (IndexSpace const* is, const Geometry& geom)
    : Level(is, geom)
{}
 
template <typename G>
GShopLevel<G>::GShopLevel (IndexSpace const* is, G const& gshop, const Geometry& geom,
                           int max_grid_size, int ngrow, bool extend_domain_face, int num_crse_opt)
    : Level(is, geom)
{
    if (std::is_same_v<typename G::FunctionType, AllRegularIF>) {
        m_allregular = true;
        m_ok = true;
        return;
    }
 
    define_fine(gshop, geom, max_grid_size, ngrow, extend_domain_face, num_crse_opt);
}
 
template <typename G>
void
GShopLevel<G>::prepare_grids (G const& gshop, const Geometry& geom,
                              int max_grid_size, int ngrow, bool extend_domain_face, int num_crse_opt)
{
    if (amrex::Verbose() > 0 && extend_domain_face == false) {
        amrex::Print() << "AMReX WARNING: extend_domain_face=false is not recommended!\n";
    }
 
    BL_PROFILE("EB2::GShopLevel()-prepare_grids");
 
    // make sure ngrow is multiple of 16
    m_ngrow = IntVect{static_cast<int>(std::ceil(ngrow/16.)) * 16};
 
    Box const& domain = geom.Domain();
    Box domain_grown = domain;
    for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
        if (geom.isPeriodic(idim)) {
            m_ngrow[idim] = 0;
        } else {
            m_ngrow[idim] = std::min(m_ngrow[idim], domain_grown.length(idim));
        }
    }
    domain_grown.grow(m_ngrow);
    m_bounding_box = (extend_domain_face) ? domain : domain_grown;
    m_bounding_box.surroundingNodes();
 
    BoxList cut_boxes;
    BoxList covered_boxes;
 
    const int nprocs = ParallelContext::NProcsSub();
    const int iproc = ParallelContext::MyProcSub();
 
    num_crse_opt = std::max(0,std::min(8,num_crse_opt));
    for (int clev = num_crse_opt; clev >= 0; --clev) {
        IntVect crse_ratio(1 << clev);
        if (domain.coarsenable(crse_ratio)) {
            Box const& crse_bounding_box = amrex::coarsen(m_bounding_box, crse_ratio);
            Geometry const& crse_geom = amrex::coarsen(geom, crse_ratio);
            BoxList test_boxes;
            if (cut_boxes.isEmpty()) {
                covered_boxes.clear();
                test_boxes = BoxList(crse_geom.Domain());
                test_boxes.maxSize(max_grid_size);
            } else {
                test_boxes.swap(cut_boxes);
                test_boxes.coarsen(crse_ratio);
                test_boxes.maxSize(max_grid_size);
            }
 
            const Long nboxes = test_boxes.size();
            const auto& boxes = test_boxes.data();
            for (Long i = iproc; i < nboxes; i += nprocs) {
                const Box& vbx = boxes[i];
                const Box& gbx = amrex::surroundingNodes(amrex::grow(vbx,1));
                auto box_type = gshop.getBoxType(gbx&crse_bounding_box,crse_geom,RunOn::Gpu);
                if (box_type == gshop.allcovered) {
                    covered_boxes.push_back(amrex::refine(vbx, crse_ratio));
                } else if (box_type == gshop.mixedcells) {
                    cut_boxes.push_back(amrex::refine(vbx, crse_ratio));
                }
            }
 
            amrex::AllGatherBoxes(cut_boxes.data());
        }
    }
 
    amrex::AllGatherBoxes(covered_boxes.data());
 
    if (m_ngrow != 0) {
        auto grow_at_domain_boundary = [&] (BoxList& bl)
        {
            const IntVect& domlo = domain.smallEnd();
            const IntVect& domhi = domain.bigEnd();
            for (auto& b : bl) {
                for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
                    if (m_ngrow[idim] != 0) {
                        if (b.smallEnd(idim) == domlo[idim]) {
                            b.growLo(idim,m_ngrow[idim]);
                        }
                        if (b.bigEnd(idim) == domhi[idim]) {
                            b.growHi(idim,m_ngrow[idim]);
                        }
                    }
                }
            }
        };
        grow_at_domain_boundary(covered_boxes);
        grow_at_domain_boundary(cut_boxes);
    }
 
    if ( cut_boxes.isEmpty() &&
        !covered_boxes.isEmpty())
    {
        amrex::Abort("AMReX_EB2_Level.H: Domain is completely covered");
    }
 
    if (!covered_boxes.isEmpty()) {
        if (num_crse_opt > 2) { // don't want the box too big
            covered_boxes.maxSize(max_grid_size*4);
        }
        m_covered_grids = BoxArray(std::move(covered_boxes));
    }
 
    if (cut_boxes.isEmpty()) {
        m_grids = BoxArray();
        m_dmap = DistributionMapping();
        m_allregular = true;
        m_ok = true;
    } else {
        m_grids = BoxArray(std::move(cut_boxes));
        m_dmap = DistributionMapping(m_grids);
    }
}
 
template <typename G>
void
GShopLevel<G>::define_fine (G const& gshop, const Geometry& geom,
                            int max_grid_size, int ngrow, bool extend_domain_face, int num_crse_opt)
{
    BL_PROFILE("EB2::GShopLevel()-fine");
 
#ifdef AMREX_USE_FLOAT
    Real small_volfrac = 1.e-5_rt;
#else
    Real small_volfrac = 1.e-14;
#endif
    bool cover_multiple_cuts = false;
    int maxiter = 32;
    {
        ParmParse pp("eb2");
        pp.queryAdd("small_volfrac", small_volfrac);
        pp.queryAdd("cover_multiple_cuts", cover_multiple_cuts);
        pp.queryAdd("maxiter", maxiter);
    }
    maxiter = std::min(100000, maxiter);
 
    prepare_grids(gshop, geom, max_grid_size, ngrow, extend_domain_face, num_crse_opt);
 
    if (m_allregular) { return; }
 
    m_mgf.define(m_grids, m_dmap);
    const int ng = GFab::ng;
    MFInfo mf_info;
    mf_info.SetTag("EB2::Level");
    m_cellflag.define(m_grids, m_dmap, 1, ng, mf_info);
    m_volfrac.define(m_grids, m_dmap, 1, ng, mf_info);
    m_centroid.define(m_grids, m_dmap, AMREX_SPACEDIM, ng, mf_info);
    m_bndryarea.define(m_grids, m_dmap, 1, ng, mf_info);
    m_bndrycent.define(m_grids, m_dmap, AMREX_SPACEDIM, ng, mf_info);
    m_bndrynorm.define(m_grids, m_dmap, AMREX_SPACEDIM, ng, mf_info);
    for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
        m_areafrac[idim].define(amrex::convert(m_grids, IntVect::TheDimensionVector(idim)),
                                m_dmap, 1, ng, mf_info);
        m_facecent[idim].define(amrex::convert(m_grids, IntVect::TheDimensionVector(idim)),
                                m_dmap, AMREX_SPACEDIM-1, ng, mf_info);
        IntVect edge_type{1}; edge_type[idim] = 0;
        m_edgecent[idim].define(amrex::convert(m_grids, edge_type), m_dmap, 1, ng, mf_info);
    }
 
    const auto dx = geom.CellSizeArray();
    const auto problo = geom.ProbLoArray();
 
    auto bounding_box = m_bounding_box;
    for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
        if (!extend_domain_face || geom.isPeriodic(idim)) {
            bounding_box.grow(idim,GFab::ng);
        }
    }
 
    RunOn gshop_run_on = (Gpu::inLaunchRegion() && gshop.isGPUable())
        ? RunOn::Gpu : RunOn::Cpu;
 
    bool hybrid = Gpu::inLaunchRegion() && (gshop_run_on == RunOn::Cpu);
    amrex::ignore_unused(hybrid);
 
    int iter = 0;
    for (; iter < maxiter; ++iter)
    {
        int nsmallcells = 0;
        int nmulticuts = 0;
#ifdef AMREX_USE_OMP
#pragma omp parallel if (Gpu::notInLaunchRegion()) reduction(+:nsmallcells,nmulticuts)
#endif
        {
#if (AMREX_SPACEDIM == 3)
            Array<BaseFab<Real>, AMREX_SPACEDIM> M2;
            EBCellFlagFab cellflagtmp;
#endif
            for (MFIter mfi(m_mgf); mfi.isValid(); ++mfi)
            {
                auto& gfab = m_mgf[mfi];
                const Box& vbx = gfab.validbox();
 
                auto& levelset = gfab.getLevelSet();
                if (iter == 0) {
                    gshop.fillFab(levelset, geom, gshop_run_on, bounding_box);
#ifdef AMREX_USE_GPU
                    if (hybrid) {
                        levelset.prefetchToDevice();
                    }
#endif
                }
 
                auto& cellflag = m_cellflag[mfi];
 
                gfab.buildTypes(cellflag);
 
                Array4<Real const> const& clst = levelset.const_array();
                Array4<Real      > const&  lst = levelset.array();
                Array4<EBCellFlag> const& cfg = m_cellflag.array(mfi);
                Array4<Real> const& vfr = m_volfrac.array(mfi);
                Array4<Real> const& ctr = m_centroid.array(mfi);
                Array4<Real> const& bar = m_bndryarea.array(mfi);
                Array4<Real> const& bct = m_bndrycent.array(mfi);
                Array4<Real> const& bnm = m_bndrynorm.array(mfi);
                AMREX_D_TERM(Array4<Real> const& apx = m_areafrac[0].array(mfi);,
                             Array4<Real> const& apy = m_areafrac[1].array(mfi);,
                             Array4<Real> const& apz = m_areafrac[2].array(mfi););
                AMREX_D_TERM(Array4<Real> const& fcx = m_facecent[0].array(mfi);,
                             Array4<Real> const& fcy = m_facecent[1].array(mfi);,
                             Array4<Real> const& fcz = m_facecent[2].array(mfi););
 
                auto& facetype = gfab.getFaceType();
                AMREX_D_TERM(Array4<Type_t> const& ftx = facetype[0].array();,
                             Array4<Type_t> const& fty = facetype[1].array();,
                             Array4<Type_t> const& ftz = facetype[2].array(););
 
                int nmc = 0;
                int nsm = 0;
 
#if (AMREX_SPACEDIM == 3)
                auto& edgetype = gfab.getEdgeType();
                Array4<Type_t const> const& xdg = edgetype[0].const_array();
                Array4<Type_t const> const& ydg = edgetype[1].const_array();
                Array4<Type_t const> const& zdg = edgetype[2].const_array();
 
                Array4<Real> const& xip = m_edgecent[0].array(mfi);
                Array4<Real> const& yip = m_edgecent[1].array(mfi);
                Array4<Real> const& zip = m_edgecent[2].array(mfi);
 
                if (iter == 0) {
#ifdef AMREX_USE_GPU
                    if (hybrid) {
                        Gpu::streamSynchronize();
                        for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
                            edgetype[idim].prefetchToHost();
                            m_edgecent[idim][mfi].prefetchToHost();
                        }
                    }
#endif
 
                    gshop.getIntercept({xip,yip,zip}, {xdg,ydg,zdg}, clst,
                                       geom, gshop_run_on, bounding_box);
 
#ifdef AMREX_USE_GPU
                    if (hybrid) {
                        for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
                            edgetype[idim].prefetchToDevice();
                            m_edgecent[idim][mfi].prefetchToDevice();
                        }
                    }
#endif
                } else {
                    gshop.updateIntercept({xip,yip,zip}, {xdg,ydg,zdg}, clst, geom);
                }
 
                for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
                    const Box& b = facetype[idim].box();
                    M2[idim].resize(b,3);
                }
                Array4<Real> const& xm2 = M2[0].array();
                Array4<Real> const& ym2 = M2[1].array();
                Array4<Real> const& zm2 = M2[2].array();
 
                nmc = build_faces(vbx, cfg, ftx, fty, ftz, xdg, ydg, zdg, lst,
                                  xip, yip, zip, apx, apy, apz, fcx, fcy, fcz,
                                  xm2, ym2, zm2, dx, problo, cover_multiple_cuts);
 
                cellflagtmp.resize(m_cellflag[mfi].box());
                Elixir cellflagtmp_eli = cellflagtmp.elixir();
                Array4<EBCellFlag> const& cfgtmp = cellflagtmp.array();
 
                build_cells(vbx, cfg, ftx, fty, ftz, apx, apy, apz,
                            fcx, fcy, fcz, xm2, ym2, zm2, dx, vfr, ctr,
                            bar, bct, bnm, cfgtmp, lst,
                            small_volfrac, geom, extend_domain_face, cover_multiple_cuts,
                            nsm, nmc);
 
                // Because it is used in a synchronous reduction kernel in
                // build_cells, we do not need to worry about M2's lifetime.
                // But we still need to use Elixir to extend the life of
                // cellflagtmp.
 
#elif (AMREX_SPACEDIM == 2)
                Array4<Real> const& xip = m_edgecent[0].array(mfi);
                Array4<Real> const& yip = m_edgecent[1].array(mfi);
 
                if (iter == 0) {
#ifdef AMREX_USE_GPU
                    if (hybrid) {
                        Gpu::streamSynchronize();
                        for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
                            facetype[idim].prefetchToHost();
                            m_edgecent[idim][mfi].prefetchToHost();
                        }
                    }
#endif
 
                    //                         yes, factype[1] and then [0]
                    gshop.getIntercept({xip,yip},
                                       {facetype[1].const_array(), facetype[0].const_array()},
                                       clst, geom, gshop_run_on, bounding_box);
 
#ifdef AMREX_USE_GPU
                    if (hybrid) {
                        for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
                            facetype[idim].prefetchToDevice();
                            m_edgecent[idim][mfi].prefetchToDevice();
                        }
                    }
#endif
                } else {
                    gshop.updateIntercept({xip,yip},
                                          {facetype[1].const_array(), facetype[0].const_array()},
                                          clst, geom);
                }
 
                nmc = build_faces(vbx, cfg, ftx, fty, lst, xip, yip, apx, apy, fcx, fcy,
                                  dx, problo, cover_multiple_cuts, nsm);
 
                build_cells(vbx, cfg, ftx, fty, apx, apy, dx, vfr, ctr,
                            bar, bct, bnm, lst, small_volfrac, geom, extend_domain_face,
                            nsm, nmc);
#endif
                nsmallcells += nsm;
                nmulticuts  += nmc;
            }
        }
 
        ParallelAllReduce::Sum<int>({nsmallcells,nmulticuts}, ParallelContext::CommunicatorSub());
        if (nsmallcells == 0 && nmulticuts == 0) {
            break;
        } else {
            auto ls = m_mgf.getLevelSet();
            // This is an alias MultiFab, therefore FillBoundary on it is fine.
            ls.FillBoundary(geom.periodicity());
            if (amrex::Verbose() > 0) {
                if (nsmallcells) {
                    amrex::Print() << "AMReX EB: Iter. " << iter+1 << " fixed " << nsmallcells
                                   << " small cells" << '\n';
                }
                if (nmulticuts) {
                    amrex::Print() << "AMReX EB: Iter. " << iter+1 << " fixed " << nmulticuts
                                   << " multicuts" << '\n';
                }
            }
        }
    }
 
    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(iter < maxiter, "EB: failed to fix small cells");
 
#ifdef AMREX_USE_OMP
#pragma omp parallel if (Gpu::notInLaunchRegion())
#endif
    for (MFIter mfi(m_mgf); mfi.isValid(); ++mfi)
    {
        auto& gfab = m_mgf[mfi];
        auto const& levelset = gfab.getLevelSet();
        Array4<Real const> const& clst = levelset.const_array();
 
        AMREX_D_TERM(Array4<Real> const& xip = m_edgecent[0].array(mfi);,
                     Array4<Real> const& yip = m_edgecent[1].array(mfi);,
                     Array4<Real> const& zip = m_edgecent[2].array(mfi);)
#if (AMREX_SPACEDIM == 3)
        auto const& edgetype = gfab.getEdgeType();
        Array4<Type_t const> const& xdg = edgetype[0].const_array();
        Array4<Type_t const> const& ydg = edgetype[1].const_array();
        Array4<Type_t const> const& zdg = edgetype[2].const_array();
 
        intercept_to_edge_centroid(xip, yip, zip, xdg, ydg, zdg, clst, dx, problo);
 
#elif (AMREX_SPACEDIM == 2)
        auto& facetype = gfab.getFaceType();
        Array4<Type_t const> const& ftx = facetype[0].const_array();
        Array4<Type_t const> const& fty = facetype[1].const_array();
        //                                  fty then ftx
        intercept_to_edge_centroid(xip, yip, fty, ftx, clst, dx, problo);
#endif
    }
 
    m_levelset = m_mgf.getLevelSet();
 
    m_ok = true;
}
 
#if (AMREX_SPACEDIM == 3)
template <typename G>
template <typename GS>
requires (std::same_as<GS,STLtools>)
void
GShopLevel<G>::define_fine_mvmc (GS const& gshop, const Geometry& geom,
                                 int max_grid_size, int ngrow, bool extend_domain_face, int num_crse_opt)
{
    BL_PROFILE("EB2::GShopLevel()-fine-mvmc");
 
    prepare_grids(gshop, geom, max_grid_size, ngrow, extend_domain_face, num_crse_opt);
 
    if (m_allregular) { return; }
 
    MC::Initialize();
 
    m_sdf.define(amrex::convert(m_grids,IntVect(1)), m_dmap, 1, IntVect(1));
    gshop.fillSignedDistance(m_sdf, m_sdf.nGrowVect(), geom);
 
    for (MFIter mfi(m_sdf,MFItInfo().DisableDeviceSync()); mfi.isValid(); ++mfi) {
        m_marching_cubes[mfi.index()] = std::make_unique<MC::MCFab>();
    }
 
    MFItInfo info{};
 
#if defined(AMREX_USE_OMP) && !defined(AMREX_USE_GPU)
    info.SetDynamic(true);
#pragma omp parallel
#endif
    for (MFIter mfi(m_sdf,info); mfi.isValid(); ++mfi) {
        amrex::MC::marching_cubes(geom, m_sdf[mfi], *m_marching_cubes[mfi.index()]);
    }
 
    MC::write_stl("test.stl", m_marching_cubes);
 
    m_ok = false; // xxxxx TODO
}
#endif
 
template <typename G>
GShopLevel<G>::GShopLevel (IndexSpace const* is, int /*ilev*/, int max_grid_size, int /*ngrow*/,
                           const Geometry& geom, GShopLevel<G>& fineLevel)
    : Level(is, geom)
{
    if (fineLevel.isAllRegular()) {
        m_allregular = true;
        m_ok = true;
        return;
    }
 
    BL_PROFILE("EB2::GShopLevel()-coarse");
 
    const BoxArray& fine_grids = fineLevel.m_grids;
    const BoxArray& fine_covered_grids = fineLevel.m_covered_grids;
 
    const int coarse_ratio = 2;
    const int min_width = 8;
    bool coarsenable = fine_grids.coarsenable(coarse_ratio, min_width)
        && (fine_covered_grids.empty() || fine_covered_grids.coarsenable(coarse_ratio));
 
    m_ngrow = amrex::coarsen(fineLevel.m_ngrow,2);
    if (amrex::scale(m_ngrow,2) != fineLevel.m_ngrow) {
        m_ngrow = IntVect::TheZeroVector();
    }
 
    if (coarsenable)
    {
        int ierr = coarsenFromFine(fineLevel, true);
        m_ok = (ierr == 0);
    }
    else
    {
        Level fine_level_2(is, fineLevel.m_geom);
        fine_level_2.prepareForCoarsening(fineLevel, max_grid_size, amrex::scale(m_ngrow,2));
        int ierr = coarsenFromFine(fine_level_2, false);
        m_ok = (ierr == 0);
    }
}
 
template <typename G>
void
GShopLevel<G>::buildFCData (G const& gshop, int face_dir, int max_grid_size)
{
    BL_PROFILE("EB2::GShopLevel::buildFCData");
 
    AMREX_ASSERT(face_dir >= 0 && face_dir < AMREX_SPACEDIM);
 
    // Allocate FC data structure if needed
    if (!m_fc_data[face_dir]) {
        m_fc_data[face_dir] = std::make_unique<FCData>();
    }
 
    if (m_fc_data[face_dir]->m_built) { return; }
 
    if (m_allregular) {
        // An all-regular level carries no MultiFabs, and there is nothing to coarsen. Mark the
        // face-centered data built anyway so that hasFCData() is true and a face-centered factory
        // can be constructed: the fill*FC functions fill the regular values for such a level
        // without reading anything, exactly as their cell-centered counterparts do.
        m_fc_data[face_dir]->m_built = true;
        return;
    }
 
    // **********************************************************************
    // STEP1: Get or build the one-level-finer CC data
    // **********************************************************************
 
    Level const* refined_cc_level = nullptr;
    std::unique_ptr<GShopLevel<G>> transient_level;
 
    // Always create transient refined CC level to avoid grid mismatch
    // with application-defined BoxArrays (ERF EB-FC development)
    Geometry refined_geom = amrex::refine(m_geom, 2);
    transient_level = std::make_unique<GShopLevel<G>>(
        m_parent, gshop, refined_geom,
        max_grid_size, m_ngrow[0] > 0 ? m_ngrow[0] : 4, true, 0); // xxxxx TODO: should we use IndexSpace's member variables extend_domain_face and num_crse_opt?
 
    if (!transient_level->isOK()) {
        amrex::Abort("GShopLevel::buildFCData: failed to build refined level");
    }
    refined_cc_level = transient_level.get();
 
    // **********************************************************************
    // STEP2: Check multi-cut error
    // **********************************************************************
 
    // Everything below is local. m_grids, m_dmap and m_levelset describe the cell-centered
    // level that the IndexSpace hands to every EBFArrayBoxFactory built from it, so building
    // face-centered data must not touch them: overwriting m_grids would leave Level::boxArray()
    // describing a different region than the cell-centered data it belongs to, and redefining
    // m_levelset on those grids would silently change the level set that cell-centered
    // factories created afterwards report.
    //
    // The grids are coarsened from the refined level rather than taken from m_grids so that the
    // DistributionMapping stays compatible with the refined data we read below.
    const BoxArray fc_base_grids = amrex::coarsen(refined_cc_level->m_grids, 2);
    if (!refined_cc_level->m_covered_grids.empty()) {
        m_fc_data[face_dir]->m_covered_grids_fc =
            amrex::coarsen(refined_cc_level->m_covered_grids, 2).simplified();
    }
    const DistributionMapping fc_dmap = refined_cc_level->m_dmap;
 
    // Face-centered data provides no level set, so nothing here coarsens one. The multi-cut check
    // below only needs an MFIter over the coarse boxes, walking alongside the refined level set
    // that shares this DistributionMapping, so this MultiFab is declared without data.
    auto const& f_levelset = refined_cc_level->m_levelset;
    MultiFab crse_boxes(amrex::convert(fc_base_grids,IntVect::TheNodeVector()), fc_dmap, 1, 0,
                        MFInfo{}.SetAlloc(false));
 
    int mvmc_error = 0;
 
    if (Gpu::notInLaunchRegion())
    {
#ifdef AMREX_USE_OMP
#pragma omp parallel reduction(max:mvmc_error)
#endif
        for (MFIter mfi(crse_boxes,true); mfi.isValid(); ++mfi)
        {
            const Box& ccbx = mfi.tilebox(IntVect::TheCellVector());
            auto const& fine = f_levelset.const_array(mfi);
 
            int tile_error = 0;
            amrex::LoopOnCpu(ccbx,
            [=,&tile_error] (int i, int j, int k) noexcept
            {
                int ierror = check_mvmc(i,j,k,fine);
                tile_error = std::max(tile_error,ierror);
            });
 
            mvmc_error = std::max(mvmc_error, tile_error);
        }
    }
    else
    {
        ReduceOps<ReduceOpMax> reduce_op;
        ReduceData<int> reduce_data(reduce_op);
        using ReduceTuple = typename decltype(reduce_data)::Type;
 
        for (MFIter mfi(crse_boxes); mfi.isValid(); ++mfi)
        {
            const Box& ndbx = mfi.validbox();
            const Box& ccbx = amrex::enclosedCells(ndbx);
            auto const& fine = f_levelset.const_array(mfi);
            reduce_op.eval(ndbx, reduce_data,
            [=] AMREX_GPU_DEVICE (int i, int j, int k) -> ReduceTuple
            {
                int ierror;
                if (ccbx.contains(IntVect{AMREX_D_DECL(i,j,k)})) {
                    ierror = check_mvmc(i,j,k,fine);
                } else {
                    ierror = 0;
                }
                return {ierror};
            });
        }
        ReduceTuple rv = reduce_data.value(reduce_op);
        mvmc_error = amrex::max(0, amrex::get<0>(rv));
    }
 
    {
        bool b = mvmc_error;
        ParallelAllReduce::Or(b, ParallelContext::CommunicatorSub());
        mvmc_error = b;
    }
    if (mvmc_error) {
        amrex::Abort("GShopLevel::buildFCData: MVMC error");
    }
 
    // **********************************************************************
    // STEP3: Define FC data structures
    // **********************************************************************
 
    // FC MultiFabs
    auto& fc_cellflag = m_fc_data[face_dir]->m_cellflag_fc;
    MultiFab& fc_volfrac = m_fc_data[face_dir]->m_volfrac_fc;
    MultiFab& fc_centroid = m_fc_data[face_dir]->m_centroid_fc;
    MultiFab& fc_bndryarea = m_fc_data[face_dir]->m_bndryarea_fc;
    MultiFab& fc_bndrycent = m_fc_data[face_dir]->m_bndrycent_fc;
    MultiFab& fc_bndrynorm = m_fc_data[face_dir]->m_bndrynorm_fc;
    auto& fc_areafrac = m_fc_data[face_dir]->m_areafrac_fc;
    auto& fc_facecent = m_fc_data[face_dir]->m_facecent_fc;
    auto& fc_edgecent = m_fc_data[face_dir]->m_edgecent_fc;
 
    // Index types of the face-centered data. One rule covers all of it: face_dir is nodal,
    // because that is how a box spans staggered cells - there is one more of them than there
    // are cell-centered cells, and nodal is how AMReX says so. The remaining directions carry
    // whatever type the cell-centered path would give.
    //
    //   cellflag / volfrac / centroid / bndry*   nodal in face_dir alone, i.e. (N,C,C) for
    //                                            face_dir=0, (C,N,C) for 1, (C,C,N) for 2.
    //                                            These are the staggered cells themselves.
    //   areafrac[idim] / facecent[idim]          the same, for every idim.
    //   edgecent[idim]                           cell in idim and nodal elsewhere, as in the
    //                                            cell-centered path, with face_dir forced nodal.
    //
    // areafrac and facecent are kept uniform across idim on purpose. The cell-centered path
    // gives each direction its own nodal index type (areafrac[0] is (N,C,C), areafrac[1] is
    // (C,N,C), ...); carrying that over to a grid already staggered in face_dir would put three
    // different index types in play at once for no real gain. Here all three are simply indexed
    // by the staggered cell they belong to, and areafrac[idim](i,j,k) is that cell's low face in
    // direction idim, with areafrac[idim](i+1,j,k) its high one.
    //
    // Indexing by the staggered cell is why face_dir has to be nodal even here. The valid box
    // then holds every staggered cell the box owns, which is what coarsen_from_fine below fills
    // and what the fill*FC ParallelCopy can hand out. A cell-typed face_dir would stop one short
    // and leave the last staggered cell of every box in the ghost region, where the copy cannot
    // reach it: the covered-region mask in fill*FC would clear that plane with nothing able to
    // write it back.
 
    // Define FC MultiFabs
    BoxArray fc_grids = amrex::convert(fc_base_grids, IntVect::TheDimensionVector(face_dir));
    const int ng = 3;
    fc_cellflag.define(fc_grids, fc_dmap, 1, ng);
    fc_volfrac.define(fc_grids, fc_dmap, 1, ng);
    fc_centroid.define(fc_grids, fc_dmap, AMREX_SPACEDIM, ng);
    fc_bndryarea.define(fc_grids, fc_dmap, 1, ng);
    fc_bndrycent.define(fc_grids, fc_dmap, AMREX_SPACEDIM, ng);
    fc_bndrynorm.define(fc_grids, fc_dmap, AMREX_SPACEDIM, ng);
 
    for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
        fc_areafrac[idim].define(fc_grids, fc_dmap, 1, ng);
        fc_facecent[idim].define(fc_grids, fc_dmap, AMREX_SPACEDIM-1, ng);
        fc_edgecent[idim].define(amrex::convert(fc_base_grids, Level::fcEdgeType(idim,face_dir)),
                                 fc_dmap, 1, ng);
    }
 
    // **********************************************************************
    // STEP4: Coarsen from refined CC to FC with staggered averaging
    // **********************************************************************
 
    // Fine CC MultiFabs
    auto const& cc_cellflag = refined_cc_level->m_cellflag;
    MultiFab const& cc_volfrac = refined_cc_level->m_volfrac;
    MultiFab const& cc_centroid = refined_cc_level->m_centroid;
    MultiFab const& cc_bndryarea = refined_cc_level->m_bndryarea;
    MultiFab const& cc_bndrycent = refined_cc_level->m_bndrycent;
    MultiFab const& cc_bndrynorm = refined_cc_level->m_bndrynorm;
    auto const& cc_areafrac = refined_cc_level->m_areafrac;
    auto const& cc_facecent = refined_cc_level->m_facecent;
    auto const& cc_edgecent = refined_cc_level->m_edgecent;
 
    int error = 0;
 
    if (Gpu::notInLaunchRegion())
    {
#ifdef AMREX_USE_OMP
#pragma omp parallel reduction(max:error)
#endif
        for (MFIter mfi(fc_volfrac,true); mfi.isValid(); ++mfi)
        {
            // Coarse FC arrays
            auto const& cvol = fc_volfrac.array(mfi);
            auto const& ccent = fc_centroid.array(mfi);
            auto const& cba = fc_bndryarea.array(mfi);
            auto const& cbc = fc_bndrycent.array(mfi);
            auto const& cbn = fc_bndrynorm.array(mfi);
            AMREX_D_TERM(auto const& capx = fc_areafrac[0].array(mfi);,
                         auto const& capy = fc_areafrac[1].array(mfi);,
                         auto const& capz = fc_areafrac[2].array(mfi););
            AMREX_D_TERM(auto const& cfcx = fc_facecent[0].array(mfi);,
                         auto const& cfcy = fc_facecent[1].array(mfi);,
                         auto const& cfcz = fc_facecent[2].array(mfi););
            AMREX_D_TERM(auto const& cecx = fc_edgecent[0].array(mfi);,
                         auto const& cecy = fc_edgecent[1].array(mfi);,
                         auto const& cecz = fc_edgecent[2].array(mfi););
            auto const& cflag = fc_cellflag.array(mfi);
 
            // Fine CC arrays
            auto const& fvol = cc_volfrac.const_array(mfi);
            auto const& fcent = cc_centroid.const_array(mfi);
            auto const& fba = cc_bndryarea.const_array(mfi);
            auto const& fbc = cc_bndrycent.const_array(mfi);
            auto const& fbn = cc_bndrynorm.const_array(mfi);
            AMREX_D_TERM(auto const& fapx = cc_areafrac[0].const_array(mfi);,
                         auto const& fapy = cc_areafrac[1].const_array(mfi);,
                         auto const& fapz = cc_areafrac[2].const_array(mfi););
            AMREX_D_TERM(auto const& ffcx = cc_facecent[0].const_array(mfi);,
                         auto const& ffcy = cc_facecent[1].const_array(mfi);,
                         auto const& ffcz = cc_facecent[2].const_array(mfi););
            AMREX_D_TERM(auto const& fecx = cc_edgecent[0].const_array(mfi);,
                         auto const& fecy = cc_edgecent[1].const_array(mfi);,
                         auto const& fecz = cc_edgecent[2].const_array(mfi););
            auto const& fflag = cc_cellflag.const_array(mfi);
 
            Box const& bx = mfi.validbox();
            Box const& ndgbx = mfi.grownnodaltilebox(-1,2);
 
            int tile_error = 0;
            amrex::LoopOnCpu(ndgbx,
            [=,&tile_error] (int i, int j, int k) noexcept
            {
                amrex::ignore_unused(j,k);
                int ierr = coarsen_from_fine(AMREX_D_DECL(i,j,k), bx, 2,
                                             cvol,ccent,cba,cbc,cbn,
                                             AMREX_D_DECL(capx,capy,capz),
                                             AMREX_D_DECL(cfcx,cfcy,cfcz),
                                             AMREX_D_DECL(cecx,cecy,cecz),
                                             cflag,fvol,fcent,fba,fbc,fbn,
                                             AMREX_D_DECL(fapx,fapy,fapz),
                                             AMREX_D_DECL(ffcx,ffcy,ffcz),
                                             AMREX_D_DECL(fecx,fecy,fecz),
                                             fflag, face_dir);
                tile_error = std::max(tile_error,ierr);
            });
 
            error = std::max(error,tile_error);
        }
    }
    else
    {
        ReduceOps<ReduceOpMax> reduce_op;
        ReduceData<int> reduce_data(reduce_op);
        using ReduceTuple = typename decltype(reduce_data)::Type;
 
        for (MFIter mfi(fc_volfrac); mfi.isValid(); ++mfi)
        {
            auto const& cvol = fc_volfrac.array(mfi);
            auto const& ccent = fc_centroid.array(mfi);
            auto const& cba = fc_bndryarea.array(mfi);
            auto const& cbc = fc_bndrycent.array(mfi);
            auto const& cbn = fc_bndrynorm.array(mfi);
            AMREX_D_TERM(auto const& capx = fc_areafrac[0].array(mfi);,
                         auto const& capy = fc_areafrac[1].array(mfi);,
                         auto const& capz = fc_areafrac[2].array(mfi););
            AMREX_D_TERM(auto const& cfcx = fc_facecent[0].array(mfi);,
                         auto const& cfcy = fc_facecent[1].array(mfi);,
                         auto const& cfcz = fc_facecent[2].array(mfi););
            // We use MultiArray4 instead of Array4 here
            // to be below the 2 kB kernel parameter limit for SYCL
            AMREX_D_TERM(auto const& cecx = fc_edgecent[0].arrays();,
                         auto const& cecy = fc_edgecent[1].arrays();,
                         auto const& cecz = fc_edgecent[2].arrays(););
            auto const& cflag = fc_cellflag.array(mfi);
 
            auto const& fvol = cc_volfrac.const_array(mfi);
            auto const& fcent = cc_centroid.const_array(mfi);
            auto const& fba = cc_bndryarea.const_array(mfi);
            auto const& fbc = cc_bndrycent.const_array(mfi);
            auto const& fbn = cc_bndrynorm.const_array(mfi);
            AMREX_D_TERM(auto const& fapx = cc_areafrac[0].const_array(mfi);,
                         auto const& fapy = cc_areafrac[1].const_array(mfi);,
                         auto const& fapz = cc_areafrac[2].const_array(mfi););
            AMREX_D_TERM(auto const& ffcx = cc_facecent[0].const_array(mfi);,
                         auto const& ffcy = cc_facecent[1].const_array(mfi);,
                         auto const& ffcz = cc_facecent[2].const_array(mfi););
            AMREX_D_TERM(auto const& fecx = cc_edgecent[0].const_arrays();,
                         auto const& fecy = cc_edgecent[1].const_arrays();,
                         auto const& fecz = cc_edgecent[2].const_arrays(););
            auto const& fflag = cc_cellflag.const_array(mfi);
 
            const int lidx = mfi.LocalIndex();
            Box const& bx = mfi.validbox();
            Box const& gbx = amrex::grow(bx,2);
            Box const& ndgbx = amrex::surroundingNodes(gbx);
 
            reduce_op.eval(ndgbx, reduce_data,
            [=] AMREX_GPU_DEVICE (int i, int j, int k) -> ReduceTuple
            {
                amrex::ignore_unused(j,k);
                int ierr = coarsen_from_fine(AMREX_D_DECL(i,j,k), bx, 2,
                                             cvol,ccent,cba,cbc,cbn,
                                             AMREX_D_DECL(capx,capy,capz),
                                             AMREX_D_DECL(cfcx,cfcy,cfcz),
                                             AMREX_D_DECL(cecx[lidx],cecy[lidx],cecz[lidx]),
                                             cflag,fvol,fcent,fba,fbc,fbn,
                                             AMREX_D_DECL(fapx,fapy,fapz),
                                             AMREX_D_DECL(ffcx,ffcy,ffcz),
                                             AMREX_D_DECL(fecx[lidx],fecy[lidx],fecz[lidx]),
                                             fflag, face_dir);
                return {ierr};
            });
        }
 
        ReduceTuple rv = reduce_data.value(reduce_op);
        error = amrex::max(0, amrex::get<0>(rv));
    }
 
    {
        bool b = error;
        ParallelAllReduce::Or(b, ParallelContext::CommunicatorSub());
        error = b;
    }
 
    m_fc_data[face_dir]->m_built = true;
 
    if (!error) {
        buildCellFlagFC(face_dir);
    }
}
 
}
 
#endif