docs: private final void MultiplyAv(int n, double[] v, double[] Av){
          for (int i=0; i<n; i++){
              Av[i] = 0;
              for (int j=0; j<n; j++) Av[i] += A(i,j)*v[j];
          }
      }
  
      /* multiply vector v by matrix A transposed */
      private final void MultiplyAtv(int n, double[] v, double[] Atv){
          for (int i=0;i<n;i++){
              Atv[i] = 0;
              for (int j=0; j<n; j++) Atv[i] += A(j,i)*v[j];
          }
      }
  
      /* multiply vector v by matrix A and then by matrix A transposed */
      private final void MultiplyAtAv(int n, double[] v, double[] AtAv){
          double[] u = new double[n];
          MultiplyAv(n,v,u);
          MultiplyAtv(n,u,AtAv);
      }
  }