// Cactus grid hierarchy extension

  // TODO: Remove unique_ptr once AmrCore has move constructors

#include <AMReX_MultiFabUtil.H>

void Restrict(int level);

  // Restrict
  for (int level = (ghext->leveldata.size()) - 2; level >= 0; --level)
    Restrict(level);

    CCTK_Traverse(cctkGH, "CCTK_POSTSTEP");

    // Restrict
    for (int level = (ghext->leveldata.size()) - 2; level >= 0; --level)
      Restrict(level);

    CCTK_Traverse(cctkGH, "CCTK_POSTSTEP");

void Restrict(int level) {
  auto &leveldata = ghext->leveldata.at(level);
  const auto &fineleveldata = ghext->leveldata.at(level + 1);
  for (int gi = 0; gi < int(leveldata.groupdata.size()); ++gi) {
    auto &groupdata = leveldata.groupdata.at(gi);
    const auto &finegroupdata = fineleveldata.groupdata.at(gi);
    // If there is more than one time level, then we don't restrict
    // the oldest.
    int ntls = groupdata.mfab.size();
    int restrict_tl = ntls > 1 ? ntls - 1 : ntls;
    const IntVect reffact{2, 2, 2};
    for (int tl = 0; tl < restrict_tl; ++tl) {
      amrex::average_down(*finegroupdata.mfab.at(tl), *groupdata.mfab.at(tl),
                          ghext->amrcore->Geom(level + 1),
                          ghext->amrcore->Geom(level), 0, groupdata.numvars,
                          reffact);
    }
  }
}

        tag[idx] = r <= 0.5 / cctk_levfac[0];

        tag[idx] = r <= 0.5 / cctk_levfac[0] - 0.5 * dx[0];