A = rand(80);
L = zeros(80);
U = zeros(80);
for k = 1:80
      U(k,k:80) = A(k,k:80) - L(k,1:k-1)*U(1:k-1,k:80);
      L(k+1:80,k) = (A(k+1:80,k)-L(k+1:80,1:k-1)*U(1:k-1,k))/U(k,k);
end
L = L + eye(80);
norm(L,inf)
norm(U,inf)
norm(L*U-A,inf)
[L1,U1]=lu(A);
norm(L1,inf)
norm(U1,inf)
norm(L1*U1-A,inf)
