docs: public static void outerProd(DMatrixD1 x, DMatrixD1 y, DMatrix1Row A ) {
          int m = A.numRows;
          int n = A.numCols;
  
          int index = 0;
          for( int i = 0; i < m; i++ ) {
              double xdat = x.get(i);
              for( int j = 0; j < n; j++ ) {
                  A.set(index++ ,  xdat*y.get(j) );
              }
          }
      }