struct ScalarGroupData : public CommonGroupData {
      vector<vector<CCTK_REAL> > data; // [time level][var index]
      int dimension;
      int activetimelevels;
      int lsh[dim];
      int ash[dim];
      int gsh[dim];
      int nghostzones[dim];
      int bbox[2*dim];
      int lbnd[dim];
      int ubnd[dim];
      ScalarGroupData() {
        dimension = -1;
        activetimelevels = -1;
        for (int d = 0; d < dim; d++) {
          lsh[d] = -1;
          ash[d] = -1;
          gsh[d] = -1;
          lbnd[d] = -1;
          ubnd[d] = -1;
          bbox[2*d] = bbox[2*d+1] = -1;
          nghostzones[d] = -1;
        }
      }
      friend YAML::Emitter &operator<<(YAML::Emitter &yaml,
                                       const ScalarGroupData &scalargroupdata);
    };
    // TODO: right now this is sized for the total number of groups
    vector<unique_ptr<ScalarGroupData> > scalargroupdata; // [group index]