code: private void computeSumItemSizes() {
          for (int d = 0; d < nbDims; d++) {
              long sum = 0;
              for (int i = 0; i < iSizes[d].length; i++) {
                  sum += iSizes[d][i];
              }
              this.sumISizes[d] = sum;
          }
  
      }
docs: Compute the sum of the item sizes for each dimension.