Department of Computer Science & Engineering

Well over a decade ago, many believed that an engine of growth driving the semiconductor and computing industries, captured nicely by Gordon Moore’s remarkable prophecy (Moore’s law), was speeding towards a dangerous cliff-edge. Ranging from expression of concern to doomsday scenarios, the exact time when serious hurdles would beset us varied quite a bit—some of the more optimistic warnings giving Moore’s law till 2020! Needless to say, a lot of people have spent time and effort with great success to find ways for substantially extending the time when we would encounter the dreaded cliff-edge, if not avoid it altogether. When faced with this issue, I decided to consider a different approach—one which suggested falling off the metaphorical cliff as a design choice, but in a controlled manner. This would result in devices that could switch and produce bits that are correct, namely have the intended value, only with a probabilistic guarantee. As a result, the results could in fact be incorrect. Such devices and associated circuits and computing structures are now broadly referred to as inexact designs, circuits and architectures. In this talk, I will start with the beginnings of this idea in 2002—one that Technology Review labeled as being heretical in their TR10 citation—and give an overview of a range of ideas that my students and other groups around the world have been developing since, that embody inexact computing today. Despite being probabilistic, inexact designs can be significantly more efficient in the energy they consume, their speed of execution and area needs, which makes them attractive for resilient applications which can tolerate error. I will also contrast this style of design with traditional approaches with a rich history, aimed at realizing reliable computing from unreliable elements, starting with von Neumann’s influential lectures and further developed elegantly by Shannon-Weaver and others.

Bio: Krishna V. Palem is the Ken and Audrey Kennedy Professor at Rice University with appointments in Computer Science, in Electrical and Computer Engineering and in Statistics. He founded and directed the NTU-Rice Institute on Sustainable and Applied Infodynamics (ISAID), and is a scholar in the Baker Institute for Public Policy. Concurrently, he was a Nanyang Visiting Professor in the School of Physical and Mathematical Sciences at the Nanyang Technological University (NTU), Singapore. He was a Moore Distinguished Faculty Fellow at Caltech in 2006-2007, and a Schonbrunn Fellow at the Hebrew University of Jerusalem in 1999, where he was recognized for excellence in teaching. His advisee Suren Talla was awarded the Janet Fabri Prize for outstanding dissertation in 2001, and his related work on the foundations of architecture assembly for designing reconfigurable embedded SoC architectures, developed at Proceler Inc. which he co-founded and served as a CTO, was a nominee for the Analysts Choice Awards as one of the (four) outstanding technologies of 2002.

More recently, he has pioneered a novel technology entitled Probabilistic CMOS (PCMOS) for enabling ultra low-energy embedded computing, with his students. In this context, his student Lakshmi Chakrapani's research was recognized through an outstanding dissertation award by Sigma Xi in 2008. PCMOS has also been recognized by a best-paper award at the IEEE-ACM CASES 2006 conference in Seoul, as one of the ten technologies 'likely to change the way we live' by MIT's Technology Review, and as one of the seven 'emerging world changing technologies' by IEEE as part of its 125th anniversary celebrations. Broadly, he has led efforts internationally in the area of embedded systems and their compiler optimizations, for which he has been named a Fellow of the IEEE, the ACM and AAAS. In 2012, Forbes (India) ranked him second on the list of eighteen scientists who are ``...some of the finest minds of Indian origin.” He is the recipient of the 2008 W. Wallace McDowell Award, IEEE Computer Society's highest technical award and one of computing's most prestigious individual honors.