Date:

September 4, 2015 - 4:00pm to 5:00pm

Location:

110 MLH

Speaker:

Douglas W. Jones

University of Iowa

Ternary computing (that is, computers that use base 3) may seem eccentric, but it has a history dating back to the early 1960s and there is growing interest in it today, thanks to the slow demise of Moore's Law. Ternary arithmetic requires particular attention. Multiplication and division by two, operations we take for granted to be inexpensive, are no longer trivial. I show how two n-trit (ternary digit) numbers can be added in O(log n) time, and both division by two and remainder after division by 2 can be done using O(log n) add operations. Finally, research on ternary computing requires support for ternary computing on binary computers. BCT (binary coded ternary) is an obvious solution to this problem, and I show how BCT arithmetic can be done efficiently on a binary computer.

**Bio:** Douglas Jones has been on the computer science faculty at Iowa since 1980. He has a BS in physics from Carnegie-Mellon, and an MS and PhD in computer science from the University of Illinois at Urbana. While his work for the past decade has focused on elections, a significant part of his work in the 1980s focused on discrete-event simulation, and in the 1990s, he worked on real-time control of stepping motors. His Iowa Logic Simulator was, for a time, heavily used in teaching digital logic, back when the CS department taught that, and he has worked on efficient implementation of BCD arithmetic on binary computers. All of this background comes together in his recent work on ternary computing.