The Principle of Automatic Sweeping

Hi all.

I want to know how automatic sweep of dc analysis works. 

I'm doing now a DC sweep analysis with 192 corner patterns.

In this simulation, I need to verify thresholds of a CMOS Inverter in 1 mV order sweeping the input voltage.

I've already known the rough value of the threshold(which is under 1V), so the sweeping steps need to be fine only around the threshold.

However, I also have to check the leak current at the input voltage = 0V/3.5V/5.5V.

So I want set the sweeping range from 0V to 5.5V,

but if I run this simulation with linear sweep of 1mV step from 0V to 5.5V, it takes over 1 hour.

So  I want to make sure if  sweeping step become finer when the output values abruptly changes in automatic sweeping method,

and how the principle is like. 

Thank you.