-cgm = conjugate_gradient_method(A, b, x0, 1e-6, 1000);
-pcgm = preconditioned_conjugate_gradient_method(A, M, b, x0, 1e-6, 1000);
-diff = norm(cgm - pcgm);
+cgm = conjugate_gradient_method(A, b, x0, tolerance, max_iterations);
+pcgm = preconditioned_conjugate_gradient_method(A, ...
+ M, ...
+ b, ...
+ x0, ...
+ tolerance, ...
+ max_iterations);
+diff = norm(cgm - pcgm, 'inf');