function pow_inf(A);

 [n,n] = size(A);
 nval = n
 s = eig(A);
 [d,ii] = max(abs(s));
 lam0 = s(ii);
 t = zeros(20,1);
 s = lam0*ones(20,1);

 v =  randn(n,1); v = v/norm(v,'inf');
 for j = 1:20,
    w = A*v;
    [lam, i ] = max(abs(w));
    lam = w(i);
    v = w/lam;
    t(j) = lam;
 end
 format long e
 lambda_vals_INF = [t abs(t-s)]