Thanks for your reply, and sorry for not giving complete description.
I am running transient simulation and I need to get SNR of the whole
system, and in this case I need to have 2^18 fft points, that's the
reason why my simulation takes a long time.
2)Yes I use Spectre. Sorry, that was a typo, I meant APS. The version of Spectre is 220.127.116.117.
I am just using resistors, capacitors and transistors, and all
components are real. Actually when I use VCVS as opamp, it would take
less time for a simulation to be completed.
4) I am not getting
any warning about that, so I am sure it's not a problem with the
circuit, and it's normal for my circuit to take that much time. So I'm just trying to find a way to do parallel simulation, if available, to save time.