Re: Nanosim vs. Hspice
Nanosim is useful for system level design and verification where you just want to verify your algorithms. But to simulate in circuit-level, you should use Hspice, because its algorithms are very powerful and in the most conditions can converge to the correct results. As you know, in this level the number of components are large and you will get lots of differential equations with higher orders. But other analog simulators don't have efficient algorithms for circuit-level simulation.
Regards,
KH