Formal Identification of DC Operating Points in Integrated Circuits and some Lessons in (Ir) Reproducible Research in Computational Math

IAM Seminar
October 7, 2013 10:00 pm

Speaker:  Ian Mitchell

URL for Speaker:

Location:  LSK 460

Intended Audience:  IAM members

Local Contact:

Brian Wetton

A DC operating point is an equilibrium toward which a circuit will be drawn for sufficiently nearby initial conditions when any inputs are held fixed. DC operating points may or may not be desirable features in a circuit — in an oscillator they represent lockup, but in a memory element they are the mechanism whereby discrete state is stored. Consequently, it is useful to identify a circuit’s DC operating points. Because the circuit is naturally drawn towards them, the most common technique to identifying such equilibria is through simulation; however, it is quite possible for the domain of attraction of an equilibrium to be small enough that simulation is unlikely to find it, yet large enough to cause occasional problems. In this joint work with Mohamed Zaki & Mark Greenstreet, we strung together a collection of public software from the formal verification and numerical analysis communities to rigourously identify and classify all potential DC operating points for surprisingly complex circuit models. Unfortunately, the resulting workflow has proved fragile, and significant effort would be required for reproduction and/or extension. In the second half of the talk I will discuss some tools and techniques that would have significantly improved the reproducibility of the results had they been adopted.