// Expext coarse grid data to be valid
        for (int vi = 0; vi < groupdata.numvars; ++vi)
          if (!(coarsegroupdata.valid.at(tl).at(vi).valid_int &&
                coarsegroupdata.valid.at(tl).at(vi).valid_bnd)) {
            valid_t all_valid;
            all_valid.valid_int = true;
            all_valid.valid_bnd = true;
            CCTK_VERROR(
                "MakeNewLevelFromCoarse before prolongation: Grid function "
                "\"%s\" is invalid on refinement level %d, time "
                "level %d; expected valid %s, found valid %s",
                CCTK_FullVarName(coarsegroupdata.firstvarindex + vi),
                coarseleveldata.level, tl, string(all_valid).c_str(),
                string(coarsegroupdata.valid.at(tl).at(vi)).c_str());
          }

          assert(coarsegroupdata.valid.at(tl).at(vi).valid_int &&
                 coarsegroupdata.valid.at(tl).at(vi).valid_bnd);