fastest way to evaluate $\arg\zeta\left(\frac{1}{2}+i\text{t}\right) $

Question

Possible Duplicate:
evaluation of $ \operatorname{Arg}\zeta (1/2+is) $ ??

If we consider

$$\arg\zeta\left(\frac{1}{2} + i\text{t}\right) = \text{Im }\log\zeta\left(\frac{1}{2}+i\text{t}\right)$$

for big values of '$t$' what is the FASTEST method (numerical method) to evaluate the Argument of the Riemann zeta function along the critical line?

$$\arg\zeta\left(\frac{1}{2}+i\text{t}\right) $$