code: private void setW() {
          if( saveW ) {
              W.col0 = Y.col0;
              W.col1 = Y.col1;
              W.row0 = Y.row0;
              W.row1 = Y.row1;
          } else {
              W.col1 = Y.col1 - Y.col0;
              W.row0 = Y.row0;
          }
      }
docs: Sets the submatrix of W up give Y is already configured and if it is being cached or not.