public double normF () {
      double f = 0;
      for (int i = 0; i < m; i++) {
         for (int j = 0; j < n; j++) {
            f = Maths.hypot(f,A[i][j]);
         }
      }
      return f;
   }
public double normF ( ) { double f = 0 ; for ( int i = 0 ; i < m ; i ++ ) { for ( int j = 0 ; j < n ; j ++ ) { f = Maths . hypot ( f , A [ i ] [ j ] ) ; } } return f ; }
Frobenius norm
@return    sqrt of sum of squares of all elements.